Chapter 4: Stretching for Impaired Mobility

The term mobility can be described based on two different but interrelated parameters. It is often defined as the ability of structures or segments of the body to move or be moved to allow the presence of range of motion for functional activities (functional ROM).² It can also be defined as the ability of an individual to initiate, control, or sustain active movements of the body to perform simple to complex motor skills (functional mobility).^42,124 Mobility, as it relates to functional ROM, is associated with joint integrity as well as the flexibility (i.e., extensibility of soft tissues that cross or surround joints—muscles, tendons, fascia, joint capsules, ligaments, nerves, blood vessels, skin), which are necessary for unrestricted, pain-free movements of the body during functional tasks of daily living. The ROM needed for the performance of functional activities does not necessarily mean full or "normal" ROM.

Sufficient mobility of soft tissues and ROM of joints must be supported by a requisite level of muscle strength and endurance and neuromuscular control to allow the body to accommodate to imposed stresses placed upon it during functional movement and, thus, to enable an individual to be functionally mobile. Moreover, soft tissue mobility, neuromuscular control, and muscular endurance and strength consistent with demand are thought to be an important factor in the prevention of injury or re-injury of the musculoskeletal system.^{62,72,76,81,128,139,169}

Hypomobility (restricted motion) caused by adaptive shortening of soft tissues can occur as the result of many disorders or situations. Factors include: (1) prolonged immobilization of a body segment; (2) sedentary lifestyle; (3) postural malalignment and muscle imbalances; (4) impaired muscle performance (weakness) associated with an array of musculoskeletal or neuromuscular disorders; (5) tissue trauma resulting in inflammation and pain; and (6) congenital or acquired deformities. Any factor that limits mobility—that is, causes decreased extensibility of soft tissues—may also impair muscular performance.⁸⁷ Hypomobility, in turn, can lead to activity limitations (functional limitations) and participation restrictions (disability) in a person's life.^9,20

Just as strength and endurance exercises are essential interventions to improve impaired muscle performance or reduce the risk of injury, stretching interventions become an integral component of an individualized rehabilitation program when restricted mobility adversely affects function and increases the risk of injury. Stretching exercises also are considered an important element of fitness and sport-specific conditioning programs designed to promote wellness and reduce the risk of injury or re-injury.^{62,128,139,169} Stretching is a general term used to describe any therapeutic maneuver designed to increase the extensibility of soft tissues, thereby improving flexibility and ROM by elongating (lengthening) structures that have adaptively shortened and have become hypomobile over time.^75,165

Only through a systematic examination, evaluation, and diagnosis of a patient's presenting problems can a therapist determine what structures are restricting motion and if, when, and what types of stretching procedures are indicated. Early in the rehabilitation process, manual stretching and joint mobilization/manipulation, which involve direct, "hands-on" intervention by a practitioner, may be the most appropriate techniques. Later, self-stretching exercises performed independently by a patient after careful instruction and close supervision may be a more suitable intervention. In some situations, the use of a mechanical stretching device is indicated, particularly when manual therapies have been ineffective. Regardless of the types of stretching procedures selected for an exercise program, if the gain in ROM is to become permanent, it must be complemented by an appropriate level of strength and endurance and used on a regular basis in functional activities.

The stretching interventions described in this chapter are designed to improve the extensibility of the contractile and noncontractile components of muscle-tendon units and periarticular structures. The efficacy of these interventions is explored throughout the chapter. In addition to the stretching procedures for the extremities illustrated in this chapter, self-stretching exercises for each region of the body are described and illustrated in Chapters 16 through 22. Joint mobilization procedures for extremity joints are described and illustrated in Chapter 5 and for the temporo-mandibular joints, ribs, and sacrum in Chapter 15. Spinal mobilization and manipulation techniques are presented in Chapter 16.

Flexibility

Flexibility is the ability to move a single joint or series of joints smoothly and easily through an unrestricted, pain-free ROM.^87,109 Muscle length in conjunction with joint integrity and the extensibility of periarticular soft tissues determine flexibility.² Flexibility is related to the extensibility of muscle-tendon units that cross a joint, based on their ability to relax or deform and yield to a stretch force. The arthrokinematics of the moving joint (the ability of the joint surfaces to roll and slide) as well as the ability of periarticular connective tissues to deform also affect joint ROM and an individual's overall flexibility.

Dynamic and Passive Flexibility

Dynamic flexibility. This form of flexibility, also referred to as active mobility or active ROM, is the degree to which an active muscle contraction moves a body segment through the available ROM of a joint. It is dependent on the degree to which a joint can be moved by a muscle contraction and the amount of tissue resistance met during the active movement.

Passive flexibility. This aspect of flexibility, also referred to as passive mobility or passive ROM, is the degree to which a body segment can be passively moved through the available ROM and is dependent on the extensibility of muscles and connective tissues that cross and surround a joint. Passive flexibility is a prerequisite for—but does not ensure—dynamic flexibility.

Hypomobility

Hypomobility refers to decreased mobility or restricted motion. A wide range of pathological processes can restrict movement and impair mobility. There are many factors that may contribute to hypomobility and stiffness of soft tissues, the potential loss of ROM, and the development of contractures. These factors are summarized in Table 4.1.

Contracture

Restricted motion can range from mild muscle shortening to irreversible contractures. Contracture is defined as the adaptive shortening of the muscle-tendon unit and other soft tissues that cross or surround a joint resulting in significant resistance to passive or active stretch and limitation of ROM, which may compromise functional abilities.^{11,35,53,87,113}

There is no clear delineation of how much limitation of motion from loss of soft tissue extensibility must exist to designate the limitation of motion as a contracture. In one reference,⁸⁷ contracture is defined as an almost complete loss of motion, whereas the term shortness is used to denote partial loss of motion. The same resource discourages the use of the term tightness to describe restricted motion due to adaptive shortening of soft tissue despite its common usage in the clinical and fitness settings to describe mild muscle shortening. However, another resource⁷⁵ uses the term muscle tightness to denote adaptive shortening of the contractile and noncontractile elements of muscle.

Designation of Contractures by Location

Contractures are described by identifying the action of the shortened muscle. If a patient has shortened elbow flexors and cannot fully extend the elbow, he or she is said to have an elbow flexion contracture. When a patient cannot fully abduct the leg because of shortened adductors of the hip, he or she is said to have an adduction contracture of the hip.

Contracture Versus Contraction

The terms contracture and contraction (the process of tension developing in a muscle during shortening or lengthening) are not synonymous and should not be used interchangeably.

Types of Contracture

One way to clarify what is meant by the term contracture is to describe contractures by the pathological changes in the different types of soft tissues involved.³⁴

Myostatic contracture. In a myostatic (myogenic) contracture, although the musculotendinous unit has adaptively shortened and there is a significant loss of ROM, there is no specific muscle pathology present.³⁴ From a morphological perspective, although there may be a reduction in the number of sarcomere units in series, there is no decrease in individual sarcomere length. Myostatic contractures can be resolved in a relatively short time with stretching exercises.^34,53

Pseudomyostatic contracture. Impaired mobility and limited ROM may also be the result of hypertonicity (i.e., spasticity or rigidity) associated with a central nervous system lesion, such as a cerebrovascular accident, a spinal cord injury, or traumatic brain injury.^34,53 Muscle spasm or guarding and pain may also cause a pseudomyostatic contracture. In both situations, the involved muscles appear to be in a constant state of contraction, giving rise to excessive resistance to passive stretch. Hence, the term pseudomyostatic contracture or apparent contracture is used. If neuromuscular inhibition procedures to reduce muscle tension temporarily are applied, full, passive elongation of the apparently shortened muscle is then possible.

Arthrogenic and periarticular contracture. An arthrogenic contracture is the result of intra-articular pathology. These changes may include adhesions, synovial proliferation, joint effusion, irregularities in articular cartilage, or osteophyte formation.⁵³ A periarticular contracture develops when connective tissues that cross or attach to a joint or the joint capsule lose mobility, thus restricting normal arthrokinematic motion.

Fibrotic contracture and irreversible contracture. Fibrous changes in the connective tissue of muscle and periarticular structures can cause adherence of these tissues and subsequent development of a fibrotic contracture. Although it is possible to stretch a fibrotic contracture and eventually increase ROM, it is often difficult to re-establish optimal tissue length.³⁵

Permanent loss of extensibility of soft tissues that cannot be reversed by nonsurgical intervention may occur when normal muscle tissue and organized connective tissue are replaced with a large amount of relatively nonextensible, fibrotic adhesions and scar tissue³⁵ or even heterotopic bone. These changes can occur after long periods of immobilization of tissues in a shortened position or after tissue trauma and the subsequent inflammatory response. The longer a fibrotic contracture exists or the greater the replacement of normal muscle and connective tissue with nonextensible adhesions and scar tissue or bone, the more difficult it becomes to regain optimal mobility of soft tissues and the more likely it is that the contracture will become irreversible.^35,69,155

Selective Stretching

Selective stretching is a process whereby the overall function of a patient may be improved by applying stretching techniques selectively to some muscles and joints but allowing limitation of motion to develop in other muscles or joints. When determining which muscles to stretch and which to allow to become slightly shortened, the therapist must always keep in mind the functional needs of the patient and the importance of maintaining a balance between mobility and stability for maximum functional performance.

The decision to allow restrictions to develop in selected muscle-tendon units and joints typically is made in patients with permanent paralysis. For example:

• In a patient with spinal cord injury, stability of the trunk is necessary for independence in sitting. With thoracic and cervical lesions, the patient does not have active control of the back extensors. If the hamstrings are routinely stretched to improve or maintain their extensibility and moderate hypomobility is allowed to develop in the extensors of the low back, this enables a patient to lean into the slightly shortened structures and have some degree of trunk stability for long-term sitting. However, the patient must still have enough flexibility for independence in dressing and transfers. Too much limitation of motion in the low back can decrease function.

• Allowing slight hypomobility to develop in the long flexors of the fingers while maintaining mobility of the wrist enables the patient with spinal cord injury, who lacks innervation of the intrinsic finger muscles, to regain the ability to grasp by using a tenodesis action.

Overstretching and Hypermobility

Overstretching is a stretch well beyond the normal length of muscle and ROM of a joint and the surrounding soft tissues,⁸⁷ resulting in hypermobility (excessive mobility).

• Creating selective hypermobility by overstretching may be necessary for certain healthy individuals with normal strength and stability, who participate in sports that require extensive flexibility.

• Overstretching becomes detrimental and creates joint instability when the supporting structures of a joint and the strength of the muscles around a joint are insufficient and cannot hold a joint in a stable, functional position during activities. Instability of a joint often causes pain and may predispose a person to musculoskeletal injury.

Overview of Interventions to Increase Mobility of Soft Tissues

Many therapeutic interventions have been designed to improve the mobility of soft tissues and consequently, increase ROM and flexibility. Stretching and mobilization/manipulation are general terms that describe any therapeutic maneuver that increases the extensibility of restricted soft tissues.

The following are terms that describe a number of techniques designed to increase soft tissue extensibility and joint mobility, only some of which are addressed in depth in this chapter.

Stretching: Manual or Mechanical/Passive or Assisted

A sustained or intermittent external, end-range stretch force, applied with overpressure and by manual contact or a mechanical device, elongates a shortened muscle-tendon unit and periarticular connective tissues by moving a restricted joint just past the available ROM. If the patient is as relaxed as possible, it is called passive stretching. If the patient assists in moving the joint through a greater range, it is called assisted stretching.

Self-Stretching

Any stretching exercise that is carried out independently by a patient after instruction and supervision by a therapist is referred to as self-stretching. The terms self-stretching and flexibility exercises are often used interchangeably. However, some practitioners prefer to limit the definition of flexibility exercises to stretching exercises that are part of a general conditioning and fitness program carried out by individuals without mobility impairments. Active stretching is another term sometimes used to denote self-stretching procedures. However, stretching exercises that incorporate inhibition or facilitation techniques into stretching maneuvers also have been referred to as active stretching.¹⁶⁸

Neuromuscular Facilitation and Inhibition Techniques

Neuromuscular facilitation and inhibition procedures are purported to relax tension in shortened muscles reflexively prior to or during muscle elongation. Because the use of inhibition or facilitation techniques to assist with muscle elongation is associated with an approach to exercise known as proprioceptive neuromuscular facilitation (PNF),^145,158 many clinicians and some authors refer to these combined inhibition/facilitation/ muscle lengthening procedures by a number of terms, including PNF stretching,^31,38,138 active inhibition,⁷⁵ active stretching,¹⁶⁸ or facilitated stretching.¹²⁵ Stretching procedures based on principles of PNF are discussed in a later section of this chapter.

Muscle Energy Techniques

Muscle energy techniques are manipulative procedures that have evolved out of osteopathic medicine and are designed to lengthen muscle and fascia and to mobilize joints.^23,28,167 The procedures employ voluntary muscle contractions by the patient in a precisely controlled direction and intensity against a counterforce applied by the practitioner. Because principles of neuromuscular inhibition are incorporated into this approach, another term used to describe these techniques is postisometric relaxation.

Joint Mobilization/Manipulation

Joint manipulative techniques are skilled manual therapy interventions specifically applied to joint structures to modulate pain and treat joint impairments that limit ROM.^70,83 Principles of use and basic techniques for the extremity joints are described and illustrated in detail in Chapter 5. Mobilization with movement techniques for the extremities are described and illustrated throughout the regional chapters (see Chapters 17 to 22). Techniques for the ribs, sacrum, and temporomandibular joints are presented in Chapter 15, and spinal techniques are in Chapter 16.

Soft Tissue Mobilization/Manipulation

Soft tissue manipulative techniques are designed to improve muscle extensibility and involve the application of specific and progressive manual forces (e.g., by means of sustained manual pressure or slow, deep stroking) to effect change in the myofascial structures that can bind soft tissues and impair mobility. Techniques, including friction massage,^75,147 myofascial release,^{22,68,100,147} acupressure,^75,147,157 and trigger point therapy,^100,147,157 are designed to improve tissue mobility by manipulating connective tissue that binds soft tissues. Although they are useful adjuncts to manual stretching procedures, specific techniques are not described in this textbook.

Neural Tissue Mobilization (Neuromeningeal Mobilization)

After trauma or surgical procedures, adhesions or scar tissue may form around the meninges and nerve roots or at the site of injury at the plexus or peripheral nerves. Tension placed on the adhesions or scar tissue leads to pain or neurological symptoms. After tests to determine neural tissue mobility are conducted, the neural pathway is mobilized through selective procedures.^21,75 These maneuvers are described in Chapter 13.

Indications and Contraindications for Stretching

There are situations in which stretching exercises are appropriate and safe; however, there are also instances when stretching should not be implemented. Boxes 4.1 and 4.2 list indications and contraindications for the use of stretching interventions.

Potential Benefits and Outcomes of Stretching

Increased Flexibility and ROM

The primary effect and expected outcome of a program of stretching exercises is to restore or increase the extensibility of the muscle-tendon unit and, therefore, regain or achieve the flexibility and ROM required for necessary or desired functional activities. A considerable body of evidence has shown that the various types of stretching exercises, particularly static and PNF stretching procedures, improve flexibility and increase ROM. (The parameters of stretching exercises that determine effectiveness, such as intensity, duration, and frequency, necessary to improve flexibility and ROM are discussed later in this chapter.)

The underlying mechanisms for stretch-induced gains in ROM include biomechanical and neural changes in the contractile and noncontractile elements of the muscle-tendon unit. These changes are thought to be the result of increased muscle extensibility and length or decreased muscle stiffness (passive muscle-tendon tension).^{57,106,108,114,133} (These underlying effects are discussed in the next section of this chapter.) There is also speculation that increased ROM following stretching may be the result, at least in part, of a change in an individual's perception or tolerance of the sensation associated with stretching.^93,162

General Fitness

In addition to improving flexibility and ROM, stretching exercises routinely are recommended for warm-up prior to or cool-down following strenuous physical activity. They are also considered to be an essential part of conditioning programs for general fitness, for recreational or workplace activities, and for training in preparation for competitive sports.

Other Potential Benefits

Potential benefits and outcomes traditionally attributed to stretching exercises by practitioners include the prevention or reduction of the risk of soft tissue injuries, reduced postexercise (delayed onset) muscle soreness, and enhanced physical performance.^{48,72,76,81,139,144,170} However, the evidence to support these assumptions is inconclusive.

Injury prevention and reduced postexercise muscle soreness. Although decreased flexibility has been shown to be associated with a greater risk of musculotendinous injuries in the lower extremities,¹⁶⁹ the question of whether a program of stretching exercises can prevent or reduce the risk of injuries has not been answered conclusively. Few studies have suggested that stretching, as part of a warm-up routine immediately before vigorous physical activity, prevents or reduces the risk of injury. The vast majority of studies, analyzed in several critical reviews of the literature, have indicated that there is little, if any, link between an acute bout of stretching for warm-up prior to a strenuous event and the prevention or reduction of the likelihood of soft tissue injuries ^{73,128,133,150} or the severity or duration of postexercise, delayed-onset muscle soreness.⁷³

Enhanced performance. Another suggested benefit and outcome frequently attributed to stretching is enhanced physical performance, such as increased muscular strength, power, or endurance or improvements in physical functioning, including walking or running speed and jumping abilities.

Consequently, it is common practice for an individual, who is participating in a fitness or sport-related training program, to perform stretching exercises prior to a strength training session. Stretching is also commonly performed just before participation in an athletic event requiring strength or power, such as sprinting or performing a vertical jump. However, neither practice is based on sound scientific evidence.

To effectively evaluate the impact of stretching on physical performance, a distinction must be made between a bout of stretching carried out just before a strenuous activity (acute or pre-event stretching) and a program of stretching exercises performed on a regular basis over a period of weeks (chronic stretching). A systematic review of the literature¹³² and subsequent studies³² indicate that acute stretching either has no effect or decreases—rather than enhances—muscle performance (strength, power, or endurance) immediately following the stretching session. Acute stretching also provides no benefit or has a negative effect on the performance of activities that require strength, such as sprinting or jumping.^{57,117,132,140}

Based on a limited number of studies, performing stretching exercises as part of a comprehensive conditioning program on a regular basis over a period of weeks (chronic stretching) not only increases flexibility but also appears to have beneficial effects on physical performance. This approach to stretching has been found to improve strength or power^{64,91,132,140,170} perhaps because of an alteration in the length-tension relationships of the stretched muscles. Participating in a stretching program on a regular basis also has been shown to improve gait economy^63,64 and enhance the performance of physical activities, such as sprinting and jumping abilities.^132,140

The ability of the body to move freely—that is, without restrictions and with control during functional activities—is dependent on the passive extensibility of soft tissues as well as active neuromuscular control. Motion is necessary for the health of tissues in the body.¹¹⁵ As mentioned previously, the soft tissues that can become restricted and impair mobility are muscles with their contractile and noncontractile elements and various types of connective tissue (tendons, ligaments, joint capsules, fascia, skin). For the most part, decreased extensibility of connective tissue, not the contractile elements of muscle tissue, is the primary cause of restricted ROM in both healthy individuals and patients with impaired mobility as the result of injury, disease, or surgery.

Morphological adaptations of tissues often accompany immobilization. Each type of soft tissue has unique properties that affect its response to immobilization and its ability to regain extensibility after immobilization. When stretching procedures are applied to these soft tissues, the direction, velocity, intensity (magnitude), duration, and frequency of the stretch force as well as tissue temperature, tension, and stiffness affect the responses of the various types of soft tissue and the outcome of stretching programs.

Mechanical characteristics of contractile and noncontractile soft tissue and the neurophysiological properties of contractile tissue affect tissue lengthening. Aside from these properties, there is also some thought that increased extensibility of the muscle-tendon unit following stretching is the result of a modification of the sensation of stretch, such as the onset of end-range discomfort, perceived by an individual.^108,162

Most of the information on the biomechanical, biochemical, and neurophysiological responses of soft tissues to immobilization and remobilization is derived from animal studies; as such, the exact physiological mechanism by which stretching procedures produce an increase in the extensibility of human tissues is still unclear. However, recent studies using ultrasound imaging on musculotendinous tissue in a noninvasive in vivo state in humans have provided confirmation of previous experiments on tendon adaptability to stress using isolated material.^92,105 An understanding of the properties of these tissues and their responses to immobilization and stretch is the basis for selecting and applying the safest, most effective stretching procedures in a therapeutic exercise program for patients with impaired mobility.^63,64

When soft tissue is stretched, elastic, viscoelastic, or plastic changes occur. Both contractile and noncontractile tissues have elastic and plastic qualities; however, only noncontractile connective tissues, not the contractile elements of muscle, have viscoelastic properties.

• Elasticity is the ability of soft tissue to return to its pre-stretch resting length directly after a short-duration stretch force has been removed.^{26,40,96,97,119}

• Viscoelasticity, or viscoelastic deformation, is a time-dependent property of soft tissue that initially resists deformation, such as a change in length, of the tissue when a stretch force is first applied. If a stretch force is sustained, viscoelasticity allows a change in the length of the tissue and then enables the tissue to return gradually to its prestretch state after the stretch force has been removed.^{96,106,107,119,149,162}

• Plasticity, or plastic deformation, is the tendency of soft tissue to assume a new and greater length after the stretch force has been removed.^{59,96,155,162}

Mechanical Properties of Contractile Tissue

Muscle is composed of both contractile and noncontractile connective tissues. The contractile elements of muscle (Fig. 4.1) give it the characteristics of contractility and irritability.

The noncontractile connective tissue in and around muscle (Fig. 4.2) has the same properties as all connective tissue, including the ability to resist deforming forces.^26,106,107 The connective tissue structures, which act as a "harness" of a muscle, are the endomysium, which is the innermost layer that separates individual muscle fibers and myofibrils; the perimysium, which encases fiber bundles; and the epimysium, which is the enveloping fascial sheath around the entire muscle. It is the connective tissue framework of muscle that is the primary source of a muscle's resistance to passive elongation.^26,35,119 When contractures develop, adhesions in and between collagen fibers resist and restrict movement.³⁵

Contractile Elements of Muscle

Individual muscles are composed of many muscle fibers that lie in parallel with one another. A single muscle fiber is made up of many myofibrils. Each myofibril is composed of even smaller structures called sarcomeres, which lie in series (end-to-end) within a myofibril. The sarcomere is the contractile unit of the myofibril and is composed of overlapping myofilaments of actin and myosin that form cross-bridges. The sarcomere gives a muscle its ability to contract and relax. When a motor unit stimulates a muscle to contract, the actin-myosin filaments slide together, and the muscle actively shortens. When a muscle relaxes, the cross-bridges slide apart slightly, and the muscle returns to its resting length (Fig. 4.3).

Mechanical Response of the Contractile Unit to Stretch and Immobilization

There are a number of changes that occur over time in the anatomical structure and physiological function of the contractile units (sarcomeres) in muscle if a muscle is stretched during an exercise or if it is immobilized in either a lengthened or shortened position for an extended period of time and then remobilized. A discussion of these changes follows. Of course, the noncontractile structures in and around muscle also affect a muscle's response to stretch and immobilization.^33,96,149 Those responses and adaptations are discussed later in the chapter.

Response to Stretch

When a muscle is stretched and elongates, the stretch force is transmitted to the muscle fibers via connective tissue (endomysium and perimysium) in and around the fibers. It is hypothesized that molecular interactions link these non-contractile elements to the contractile unit of muscle, the sarcomere.⁴⁰

During passive stretch, both longitudinal and lateral force transduction occurs.⁴⁰ When initial lengthening occurs in the series elastic (connective tissue) component, tension rises sharply. After a point, there is mechanical disruption (influenced by neural and biochemical changes) of the cross-bridges as the filaments slide apart, leading to abrupt lengthening of the sarcomeres,^40,56,96,97 sometimes referred to as sarcomere give.⁵⁶ When the stretch force is released, the individual sarcomeres return to their resting length ^40,96,97 (see Fig. 4.3). As noted previously, the tendency of muscle to return to its resting length after short-term stretch is called elasticity. If longer lasting or more permanent (viscoelastic or plastic) length increases are to occur, the stretch force must be maintained over an extended period of time.^40,96,162

Response to Immobilization and Remobilization

Morphological changes. If a muscle is immobilized for a prolonged period of time, the muscle is not used during functional activities, and consequently, the physical stresses placed on the muscle are substantially diminished. This results in decay of contractile protein in the immobilized muscle, as well as decreases in muscle fiber diameter, the number of myofibrils, and intramuscular capillary density, the outcome of which is muscle atrophy and weakness (decreased force-generating capacity of muscle).^{12,19,65,82,85,96,115,151} As the immobilized muscle atrophies, an increase in fibrous and fatty tissue in muscle also occurs.¹¹⁵

The composition of muscle affects its response to immobilization, with atrophy occurring more quickly and more extensively in tonic (slow-twitch) postural muscle fibers than in phasic (fast-twitch) fibers.^96,97 The duration and position of immobilization also affect the extent of atrophy and loss of strength and power. The longer the duration of immobilization, the greater is the atrophy of muscle and loss of functional strength. Atrophy can begin within as little as a few days to a week.^84,85,151 Not only is there a decrease in the cross-sectional size of muscle fibers over time, an even more significant deterioration in motor unit recruitment occurs as reflected by electromyographic (EMG) activity.^96,97 Both compromise the force-producing capabilities of the muscle.

Immobilization in a shortened position. As documented in animal models, when a muscle is immobilized in a shortened position for several weeks, which is often necessary after a fracture or surgical repair of a muscle tear or tendon rupture, there is a reduction in the length of the muscle and its fibers and in the number of sarcomeres in series within myofibrils as the result of sarcomere absorption.^82,96,146 This absorption occurs at a faster rate than the muscle's ability to regenerate sarcomeres in an attempt to restore itself. The decrease in the overall length of the muscle fibers and their in-series sarcomeres, in turn, contributes to muscle atrophy and weakness. It has also been suggested that a muscle immobilized in a shortened position atrophies and weakens at a faster rate than if it is held in a lengthened position over time.¹⁹

There is a shift to the left in the length-tension curve of a shortened muscle, which decreases the muscle's capacity to produce maximum tension at its normal resting length as it contracts.²⁶ The increased proportion of fibrous tissue and subcutaneous fat in muscle that occurs with immobilization contributes to the decreased extensibility of the shortened muscle but may also serve to protect the weakened muscle when it stretches.^35,65

Immobilization in a lengthened position. Sometimes a limb is immobilized in a position of maximum available length for a prolonged period of time. This occurs with some surgical procedures, such as a limb lengthening,¹³ the application of a series of positional casts (serial casts),⁷⁷ or the use of a dynamic splint to stretch a long-standing contracture and increase ROM.^11,110 There is some evidence from animal studies,¹⁴⁶ but very limited evidence from studies involving human skeletal muscle,¹³ to suggest that if a muscle is held in a lengthened position for an extended time period, it adapts by increasing the number of sarcomeres in series, sometimes referred to as myofibrillogenesis.⁴⁰ It is theorized that sarcomere number addition occurs to maintain the greatest functional overlap of actin and myosin filaments in the muscle⁹⁶ and may lead to a relatively permanent (plastic) form of muscle lengthening if the newly gained length is used on a regular basis in functional activities.

The minimum time frame necessary for a stretched muscle (fiber) to become a longer muscle (fiber) by adding sarcomeres in series is not known. In animal studies that have reported increased muscle length as the result of sarcomere number addition, the stretched muscle was continuously immobilized in a lengthened position for several weeks.⁹⁶ There is often speculation in the clinical setting, rather than direct evidence, that this same process occurs and contributes to gains in muscle length (indirectly identified by increases in joint ROM) following the use of serial casts,77 dynamic splints,110 and perhaps as the result of stretching exercises.⁴⁰ However, direct evidence of sarcomere adaptation in human skeletal muscle recently was reported following long-term, continuous limb distraction to achieve lengthening of a patient's femur.¹³

The adaptation of the contractile units of muscle (an increase or decrease in the number of sarcomeres) to prolonged positioning in either lengthened or shortened positions is transient, lasting only 3 to 5 weeks if the muscle resumes its pre-immobilization use and degree of lengthening for functional activities.^85,96 In clinical situations, this underscores the need for patients to use full-range motions during a variety of functional activities to maintain the stretch-induced gains in muscle extensibility and joint ROM.

Neurophysiological Properties of Contractile Tissue

The neurophysiological properties of the muscle-tendon unit also may influence a muscle's response to stretch and the effectiveness of stretching interventions to elongate muscle.

In particular, two sensory organs of muscle-tendon units, the muscle spindle and the Golgi tendon organ, are mechanoreceptors that convey information to the central nervous system about what is occurring in a muscle-tendon unit and that affect a muscle's response to stretch.

Muscle Spindle

The muscle spindle is the major sensory organ of muscle and is sensitive to quick and sustained (tonic) stretch (Fig. 4.4). The main function of muscle spindles is to receive and convey information about changes in the length of a muscle and the velocity of the length changes.

Muscle spindles are small, encapsulated receptors composed of afferent sensory fiber endings, efferent motor fiber endings, and specialized muscle fibers called intrafusal fibers. Intrafusal muscle fibers are bundled together and lie between and parallel to extrafusal muscle fibers that make up the main body of a skeletal muscle.^{65,78,101,127} Because intrafusal muscle fibers connect at their ends to extrafusal muscle fibers, when a muscle is stretched, intrafusal fibers are also stretched. Only the ends (polar regions), not the central portion (equatorial region), of an intrafusal fiber are contractile. Consequently, when an intrafusal muscle fiber is stimulated and contracts, it lengthens the central portion. Small-diameter motor neurons, known as gamma motor neurons, innervate the contractile polar regions of intrafusal muscle fibers and adjust the sensitivity of muscle spindles. Large-diameter alpha motor neurons innervate extrafusal fibers.

There are two general types of intrafusal fiber: nuclear bag fibers and nuclear chain fibers, so named because of the arrangement of their nuclei in the central portions of the fibers. Primary (type Ia fiber) afferent endings, which arise from nuclear bag fibers, sense and cause muscle to respond to both quick and sustained (tonic) stretch. However, secondary (type II) afferents from the nuclear chain fibers are sensitive only to tonic stretch. Primary and secondary fibers synapse on the alpha or gamma motoneurons, which when stimulated cause excitation of their own extrafusal and intrafusal fibers, respectively. There are essentially two ways to stimulate these sensory fibers by means of stretch—one is by overall lengthening of the muscle; the other is by stimulating contraction of intrafusal fibers via the gamma efferent neural pathways.

Golgi Tendon Organ

The Golgi tendon organ (GTO) is a sensory organ located near the musculotendinous junctions of extrafusal muscle fibers. The function of a GTO is to monitor changes in tension of muscle-tendon units. These encapsulated nerve endings are woven among collagen strands of a tendon and transmit sensory information via Ib fibers. These sensory organs are sensitive to even slight changes of tension on a muscle-tendon unit as the result of passive stretch of a muscle or with active muscle contractions during normal movement.

When tension develops in a muscle, the GTO fires, inhibits alpha motoneuron activity, and decreases tension in the muscle-tendon unit being stretched.^24,65,78,127 With respect to the neuromuscular system, inhibition is a state of decreased neuronal activity and altered synaptic potential, which reflexively diminishes the capacity of a muscle to contract.^76,78,101

Originally, the GTO was thought to fire and inhibit muscle activation only in the presence of high levels of muscle tension as a protective mechanism. However, the GTO has since been shown to have a low threshold for firing (fires easily), so it can continuously monitor and adjust the force of active muscle contractions during movement or the tension in muscle during passive stretch.^58,127

Neurophysiological Response of Muscle to Stretch

When a stretch force is applied to a muscle-tendon unit either quickly or over a prolonged period of time, the primary and secondary afferents of intrafusal muscle fibers sense the length changes and activate extrafusal muscle fibers via alpha motor neurons in the spinal cord, thus activating the stretch reflex and increasing (facilitating) tension in the muscle being stretched. The increased tension causes resistance to lengthening and, in turn, is thought to compromise the effectiveness of the stretching procedure.^8,44 When the stretch reflex is activated in a muscle being lengthened, decreased activity (inhibition) in the muscle on the opposite side of the joint, referred to as reciprocal inhibition, also may occur.^101,158 However, this phenomenon has been documented only in studies using animal models.^{24,98,138,162} To minimize activation of the stretch reflex and the subsequent increase in muscle tension and reflexive resistance to muscle lengthening during stretching procedures, a slowly applied, low-intensity, prolonged stretch is considered preferable to a quickly applied, short-duration stretch.

In contrast, the GTO, as it monitors tension in the muscle fibers being stretched, has an inhibitory impact on the level of muscle tension in the muscle-tendon unit in which it lies, particularly if the stretch force is prolonged. This effect is called autogenic inhibition.^65,101,127 Inhibition of the contractile components of muscle by the GTO is thought to contribute to reflexive muscle relaxation during a stretching maneuver, enabling a muscle to be elongated against less muscle tension. Consequently, if a low-intensity, slow stretch force is applied to muscle, the stretch reflex is less likely to be activated as the GTO fires and inhibits tension in the muscle, allowing the parallel elastic component (the sarcomeres) of the muscle to remain relaxed and to lengthen.

In summary, when critically analyzing studies of the mechanical and neurophysiological properties of muscle, current thinking suggests that improvement in muscle extensibility attributed to stretching procedures is more likely due to tensile stresses placed on the viscoelastic, noncontractile connective tissue in and around muscle than to inhibition (reflexive relaxation) of the contractile elements of muscle.^{24,106,107,108,138,149} A discussion of the effects of stretching on noncontractile soft tissue follows.

Mechanical Properties of Noncontractile Soft Tissue

Noncontractile soft tissue permeates the entire body and is organized into various types of connective tissue to support the structures of the body. Ligaments, tendons, joint capsules, fasciae, noncontractile tissue in muscles (see Fig. 4.2), and skin have connective tissue characteristics that can lead to the development of adhesions and contractures and, thus, affect the flexibility of the tissues crossing joints. When these tissues restrict ROM and require stretching, it is important to understand how they respond to the intensity and duration of stretch forces and to recognize that the only way to increase the extensibility of connective tissue is to remodel its basic architecture.³⁵

Composition of Connective Tissue

Connective tissue is composed of three types of fiber: collagen, elastin and reticulin, and nonfibrous ground substance (proteoglycans and glycoproteins).^36,69,155

Collagen fibers. Collagen fibers are responsible for the strength and stiffness of tissue and resist tensile deformation. Tropocollagen crystals form the building blocks of collagen microfibrils. Each additional level of composition of the fibers is arranged in an organized relationship and dimension (Fig. 4.5). There are six classes with 19 types³¹ of collagen; the fibers of tendons and ligaments mostly contain type I collagen, which is highly resistant to tension.¹⁵⁵ As collagen fibers develop and mature, they bind together, initially with unstable hydrogen bonding, which then converts to stable covalent bonding. The stronger the bonds, the greater is the mechanical stability of the tissue. Tissue with a greater proportion of collagen provides greater stability.

Elastin fibers. Elastin fibers provide extensibility. They show a great deal of elongation with small loads and fail abruptly without deformation at higher loads. Tissues with greater amounts of elastin have greater flexibility.

Reticulin fibers. Reticulin fibers provide tissue with bulk.

Ground substance. Ground substance is made up of proteoglycans (PGs) and glycoproteins. The PGs function to hydrate the matrix, stabilize the collagen networks, and resist compressive forces. (This is most important in cartilage and intervertebral discs.) The type and amount of PGs are proportional to the types of compressive and tensile stress that the tissue undergoes.³⁶ The glycoproteins provide linkage between the matrix components and between the cells and matrix opponents. In essence, the ground substance is mostly an organic gel containing water that reduces friction between fibers, transports nutrients and metabolites, and may help prevent excessive cross-linking between fibers by maintaining space between fibers.^45,155

Mechanical Behavior of Noncontractile Tissue

The mechanical behavior of the various noncontractile tissues is determined by the proportion of collagen and elastin fibers and by the structural orientation of the fibers. The proportion of proteoglycans (PGs) also influences the mechanical properties of connective tissue. Those tissues that withstand high tensile loads are high in collagen fibers; those that withstand greater compressive loads have greater concentrations of PGs. The composition of the tissue changes when the load changes.³⁶

Collagen is the structural element that absorbs most of the tensile stress. Its mechanical behavior is explained with reference to the stress-strain curve described in the following paragraphs. Collagen fibers elongate quickly under light loads (wavy fibers align and straighten). With increased loads, tension in the fibers increases, and the fibers stiffen. The fibers strongly resist the tensile force, but with continued loading, the bonds between collagen fibers begin to break. When a substantial number of bonds are broken, the fibers fail. When tensile forces are applied, the maximum elongation of collagen is less than 10%, whereas elastin may lengthen 150% and return to its original configuration. Collagen is five times as strong as elastin. The alignment of collagen fibers in various tissues reflects the tensile forces acting on that tissue (see Fig. 4.5):

• In tendons, collagen fibers are parallel and can resist the greatest tensile load. They transmit forces to the bone created by the muscle.

• In skin, collagen fibers are random and weakest in resisting tension.

• In ligaments, joint capsules, and fasciae, the collagen fibers vary between the two extremes, and they resist multidirectional forces. Ligaments that resist major joint stresses have a more parallel orientation of collagen fibers and a larger cross-sectional area.¹²¹

Interpreting Mechanical Behavior of Connective Tissue: The Stress-Strain Curve

The stress-strain curve illustrates the mechanical strength of structures (Fig. 4.6) and is used to interpret what is happening to connective tissue under stress loads.^36,153,155 When a tensile force is applied to a structure, it produces elongation; the stress-strain curve illustrates the strength properties, stiffness, and amount of energy the material can store before failure of the structure.

• Stress is force (or load) per unit area. Mechanical stress is the internal reaction or resistance to an external load.

• Strain is the amount of deformation or lengthening that occurs when a load (or stretch force) is applied.

Types of Stress

There are three kinds of stress that cause strain to structures:

• Tension—a force applied perpendicular to the cross-sectional area of the tissue in a direction away from the tissue. A stretching force is a tension stress.

• Compression—a force applied perpendicular to the cross-sectional area of the tissue in a direction toward the tissue. Muscle contraction and loading of a joint during weight bearing cause compression stresses in joints.

• Shear—a force applied parallel to the cross-sectional area of the tissue.

Regions of the Stress-Strain Curve

Toe region. That area of the stress-strain curve in which there is considerable deformation without the use of much force is called the toe region. This is the range in which most functional activity normally occurs. Collagen fibers at rest are wavy and are situated in a three-dimensional matrix, so some distensibility in the tissue occurs by straightening and aligning the fibers.

Elastic range/linear phase. Strain is directly proportional to the ability of tissue to resist the force. This occurs when tissue is taken to the end of its ROM, and gentle stretch is applied. With stress in this phase, the collagen fibers line up with the applied force; the bonds between fibers and between the surrounding matrix are strained; some microfailure between the collagen bonds begins; and some water may be displaced from the ground substance. There is complete recovery from this deformation, and the tissue returns to its original size and shape when the load is released if the stress is not maintained for any length of time. (See the following discussion on creep and stress-relaxation for prolonged stretch.)

Elastic limit. The point beyond which the tissue does not return to its original shape and size is the elastic limit.

Plastic range. The range beyond the elastic limit extending to the point of rupture is the plastic range. Tissue strained in this range has permanent deformation when the stress is released. In this range, there is sequential failure (microfailure) of the bonds between collagen fibrils and eventually of collagen fibers. Heat is released and absorbed in the tissue. Because collagen is crystalline, individual fibers do not stretch but, instead, rupture. In the plastic range, it is the rupturing of fibers that results in increased length and is what probably occurs during stretching procedures.

Ultimate strength. The greatest load the tissue can sustain is its ultimate strength. Once this load is reached, there is increased strain (deformation) without an increase in stress required (macrofailure). The region of necking is reached in which there is considerable weakening of the tissue, and it rapidly fails. The therapist must be cognizant of the tissue feel when stretching because as the tissue begins necking, if the stress is maintained, there could be complete tearing of the tissue. Experimentally, maximum tensile deformation of isolated collagen fibers prior to failure is 7% to 8%. Whole ligaments may withstand strain of 20% to 40%.¹²¹

Failure. Rupture of the integrity of the tissue is called failure.

Structural stiffness. The slope of the linear portion of the curve (elastic range) is known as Young's modulus or modulus of elasticity and represents the stiffness of the tissue.³⁶ Tissues with greater stiffness have a higher slope in the elastic region of the curve, and there is less elastic deformation (elongation) under stress. Contractures and scar tissue have greater stiffness, probably because of a greater degree of bonding between collagen fibers and their surrounding matrix. Tissues with less stiffness demonstrate greater elongation under similar loads.³⁶

Time and Rate Influences on Tissue Deformation

Because connective tissue has viscoelastic properties, the amount of time and the rate at which a stress (load) is applied will affect the behavior of the tissue.

Creep. When a load is applied for an extended period of time, the tissue elongates, and does not return to its original length (Fig. 4.7 A). This change in length is related to the viscosity of the tissue and is therefore time-dependent. The amount of deformation depends on the amount of force and the rate at which the force is applied. Low-magnitude loads, usually in the elastic range and applied for long periods, increase the deformation of connective tissue and allow gradual rearrangement of collagen fiber bonds (remodeling) and redistribution of water to surrounding tissues.^{35,97,149,153} Increasing the temperature of the part increases the creep and therefore the distensibility of the tissue.^160,164 Complete recovery from creep may occur over time, but not as rapidly as a single strain. Patient reaction dictates the time a specific load is tolerated.

Stress-relaxation. When a force (load) is applied to stretch a tissue and the length of the tissue is kept constant, after the initial creep, there is a decrease in the force required to maintain that length, and the tension in the tissue decreases³⁵ (Fig. 4.7 B). This, like creep, is related to the viscoelastic qualities of the connective tissue and redistribution of the water content. Stress-relaxation is the underlying principle used in prolonged stretching procedures in which the stretch position is maintained for several hours or days. Recovery (i.e., no change) versus permanent changes in length is dependent on the amount of deformation and the length of time the deformation is maintained.³⁵

Cyclic loading and connective tissue fatigue. Repetitive loading of tissue increases heat production and may cause failure below the yield point. The greater the applied load, the fewer number of cycles needed for failure. A recent study that observed damage to rabbit medial collateral ligaments under various cyclic and static loading conditions confirmed that cyclic loading caused damage (as measured by decreased modulus) earlier than static loading.¹⁵²

This principle can be used for stretching by applying repetitive (cyclic) loads at a submaximal level on successive days. The intensity of the load is determined by the patient's tolerance. A minimum load is required for this failure. Below the minimum load an apparently infinite number of cycles do not cause failure. This is the endurance limit. Examples of connective tissue fatigue from cyclic loading are stress fractures and overuse syndromes, neither of which is desired as a result of stretching. Therefore, periodically, time is allowed between bouts of cyclic stretching to allow for remodeling and healing in the new range.

Summary of Mechanical Principles for Stretching Connective Tissue

• Connective tissue deformation (stretch) occurs to different degrees at different intensities of force and at different rates of application. It requires breaking of collagen bonds and realignment of the fibers for there to be permanent elongation or increased flexibility. Failure of tissue begins as microfailure of fibrils and fibers before complete failure of the tissue occurs. Complete tissue failure can occur as a single maximal event (acute tear from a traumatic injury or manipulation that exceeds the failure point) or from repetitive submaximal stress (fatigue or stress failure from cyclic loading). Microfailure (needed for permanent lengthening) also occurs with creep, stress-relaxation, and controlled cyclic loading.

• Healing and adaptive remodeling capabilities allow the tissue to respond to repetitive and sustained loads if time is allowed between bouts. This is important for increasing both flexibility and tensile strength of the tissue. If healing and remodeling time is not allowed, a breakdown of tissue (failure) occurs as in overuse syndromes and stress fractures. Intensive stretching is usually not done every day in order to allow time for healing. If the inflammation from the microruptures is excessive, additional scar tissue, which could become more restrictive, is laid down.³⁵

• It is imperative that the individual use any newly gained range to allow the remodeling of tissue and to train the muscle to control the new range, or the tissue eventually returns to its shortened length.

Changes in Collagen Affecting Stress-Strain Response

Effects of Immobilization

There is weakening of the tissue because of collagen turnover and weak bonding between the new, nonstressed fibers. There is also adhesion formation because of greater cross-linking between disorganized collagen fibers and because of decreased effectiveness of the ground substance maintaining space and lubrication between the fibers.^45,153 The rate of return to normal tensile strength is slow. For example, after 8 weeks of immobilization, the anterior cruciate ligament in monkeys failed at 61% of maximum load; after 5 months of reconditioning, it failed at 79%; after 12 months of reconditioning, it failed at 91%.^120,122 There was also a reduction in energy absorbed and an increase in compliance (decreased stiffness) prior to failure following immobilization. Partial and near-complete recovery followed the same 5-month and 12-month pattern.¹²⁰

Effects of Inactivity (Decrease of Normal Activity)

There is a decrease in the size and amount of collagen fibers, resulting in weakening of the tissue.³⁶ There is a proportional increase in the predominance of elastin fibers, resulting in increased compliance. Recovery takes about 5 months of regular cyclic loading. Physical activity has a beneficial effect on the strength of connective tissue.

Effects of Age

There is a decrease in the maximum tensile strength and the elastic modulus, and the rate of adaptation to stress is slower. There is an increased tendency for overuse syndromes, fatigue failures, and tears with stretching.¹²¹

Effects of Corticosteroids

There is a long-lasting deleterious effect on the mechanical properties of collagen with a decrease in tensile strength.³⁶ There is fibrocyte death next to the injection site with delay in reappearance up to 15 weeks.¹²¹

Effects of Injury

Excessive tensile loading can lead to rupture of ligaments and tendons at musculotendinous junctions.³⁶ Healing follows a predictable pattern (see Chapter 10), with bridging of the rupture site with newly synthesized type III collagen. This is structurally weaker than mature type I collagen. Remodeling progresses, and eventually collagen matures to type I. Remodeling usually begins about 3 weeks postinjury and continues for several months to a year, depending on the size of the connective tissue structure and magnitude of the tear.

Other Conditions Affecting Collagen

Nutritional deficiencies, hormonal imbalances, and dialysis may predispose connective tissue to injury at lower levels of stress than normal.³⁶

As with other forms of therapeutic exercise, such as strengthening exercises and endurance training, there are a number of essential elements that determine the effectiveness and outcomes of stretching interventions. The determinants (parameters) of stretching, all of which are interrelated, include alignment and stabilization of the body during stretching; the intensity (magnitude), duration, speed, frequency, and mode (type) of stretch; and the integration of neuromuscular inhibition or facilitation and functional activities into stretching programs. By manipulating the determinants of stretching interventions, which are defined in Box 4.3, a therapist has many options from which to choose when designing stretching programs that are safe and effective and meet the needs, functional goals, and capabilities of many patients. Each of these determinants is discussed in this section of the chapter.

Many of the investigations comparing the type, intensity, duration, and frequency of stretching have been carried out with healthy, young adults as subjects. The findings and recommendations of these studies are difficult to generalize and apply to patients with long-standing contractures or other forms of tissue restriction. Therefore, many decisions, particularly those related to the type, intensity, duration, and frequency of stretching, must continue to be based on a balance of scientific evidence and sound clinical judgments by the therapist.

There are four broad categories of stretching exercises: static stretching, cyclic (intermittent) stretching, ballistic stretching, and stretching techniques based on the principles of PNF.^39,48,74,173 Each of these forms of stretching are effective in elongating muscle and increasing ROM. Each can be carried out in various manners—that is, manually or mechanically, passively or actively, and by a therapist or independently by a patient—giving rise to many terms that are used in the literature to describe stretching interventions. The stretching interventions listed in Box 4.4 are defined and discussed in this section.

Alignment and Stabilization

Just as appropriate alignment and effective stabilization are fundamental components of muscle testing and goniometry as well as ROM and strengthening exercises, they are also essential elements of effective stretching.

Alignment

Proper alignment or positioning of the patient and the specific muscles and joints to be stretched is necessary for patient comfort and stability during stretching. Alignment influences the amount of tension present in soft tissue and consequently affects the ROM available in joints. Alignment of the muscles and joint to be stretched as well as the alignment of the trunk and adjacent joints must all be considered. For example, to effectively stretch the rectus femoris (a muscle that crosses two joints), the lumbar spine and pelvis should be maintained in a neutral position as the knee is flexed and the hip extended. The pelvis should not tilt anteriorly nor should the low back hyperextend; the hip should not abduct or remain flexed (Fig. 4.8 A and B). When a patient is self-stretching to increase shoulder flexion, the trunk should be erect, not slumped (Fig. 4.9 A and B).

NOTE: Throughout this and later chapters, recommendations for appropriate alignment and positioning during stretching procedures are identified. If it is not possible for a patient to be placed in or assume the recommended postures because of discomfort, restrictions of motion of adjacent joints, inadequate neuromuscular control, or insufficient cardiopulmonary capacity, the therapist must critically analyze the situation to determine an alternative position.

Stabilization

To achieve an effective stretch of a specific muscle or muscle group and associated periarticular structures, it is imperative to stabilize (fixate) either the proximal or distal attachment site of the muscle-tendon unit being elongated. Either site may be stabilized, but for manual stretching, it is common for a therapist to stabilize the proximal attachment and move the distal segment, as shown in Figure 4.10 A.

For self-stretching procedures, a stationary object, such as a chair or a doorframe, or active muscle contractions by the patient may provide stabilization of one segment as the other segment moves. During self-stretching, it is often the distal attachment that is stabilized as the proximal segment moves (Fig. 4.10 B).

Stabilization of multiple segments of a patient's body also helps maintain the proper alignment necessary for an effective stretch. For example, when stretching the iliopsoas, the pelvis and lumbar spine must maintain a neutral position as the hip is extended to avoid stress to the low back region. Sources of stabilization include manual contacts, body weight, or a firm surface, such as a table, wall, or floor.

Intensity of Stretch

The intensity (magnitude) of a stretch force is determined by the load placed on soft tissue to elongate it. There is general agreement among clinicians and researchers that stretching should be applied at a low-intensity by means of a low-load.^{1,11,13,30,48,74,99,103} Low-intensity stretching in comparison to high-intensity stretching makes the stretching maneuver more comfortable for the patient and minimizes voluntary or involuntary muscle guarding, so a patient can either remain relaxed or assist with the stretching maneuver.

Low-intensity stretching (coupled with a long-duration of stretch) results in optimal rates of improvement in ROM without exposing tissues, possibly weakened by immobilization, to excessive loads and potential injury.^99,103 Low-intensity stretching has also been shown to elongate dense connective tissue, a significant component of chronic contractures, more effectively and with less soft tissue damage and postexercise soreness than a high-intensity stretch.³

Duration of Stretch

One of the most important decisions a therapist must make when selecting and implementing a stretching intervention (stretching exercises or use of a mechanical stretching device) is to determine the duration of stretch that is expected to be safe, effective, practical, and efficient for each situation.

The duration of stretch refers to the period of time a stretch force is applied and shortened tissues are held in a lengthened position. Duration most often refers to how long a single cycle of stretch is applied. If more than one repetition of stretch (stretch cycle) is carried out during a treatment session (which is most often the case), the cumulative time of all the stretch cycles reflects the total duration of stretch, also referred to as the total elongation time.

In general, the shorter the duration of a single stretch cycle, the greater the number of repetitions applied during a stretching session. Many combinations have been studied.

Despite many studies over several decades, there continues to be a lack of agreement on the "ideal" combination of the duration of a single stretch cycle and the number of repetitions of stretch that should be applied in a daily stretching program to achieve the greatest and most sustained stretch-induced gains in ROM or reduction of muscle stiffness. The duration of stretch must be put in context with other stretching parameters, including intensity, frequency, and mode of stretch. Key findings from a number of studies are summarized in Box 4.5.

Several descriptors are used to differentiate between a long-duration versus a short-duration stretch. Terms such as static, sustained, maintained, and prolonged are all used to describe a long-duration stretch, whereas terms such as cyclic, intermittent, or ballistic are used to characterize a short-duration stretch. There is no specific time period assigned to any of these descriptors, nor is there a time frame that distinguishes a long-duration from a short-duration stretch.

Static Stretching

Static stretching* is a commonly used method of stretching in which soft tissues are elongated just past the point of tissue resistance and then held in the lengthened position with a sustained stretch force over a period of time. Other terms used interchangeably are sustained, maintained, or prolonged stretching. The duration of static stretch is predetermined prior to stretching or is based on the patient's tolerance and response during the stretching procedure.

In research studies, the term "static stretching" has been linked to durations of a single stretch cycle ranging from as few as 5 seconds to 5 minutes per repetition when either a manual stretch or self-stretching procedure is employed. ^† If a mechanical device provides the static stretch, the time frame can range from almost an hour to several days or weeks.^{17,77,80,99,103,110} (See additional information on mechanical stretching later in this section.)

Static stretching is well accepted as an effective form of stretching to increase flexibility and ROM^{1,39,74,75,93,118,133,162} and has been considered a safer form of stretching than ballistic stretching for decades.⁴³ Early research established that tension created in muscle during static stretching is approximately half that created during ballistic stretching.¹⁵⁹ This is consistent with our current understanding of the viscoelastic properties of connective tissue, which lies in and around muscles, as well as the neurophysiological properties of the contractile elements of muscle.

As discussed in the previous section of this chapter, non-contractile soft tissues are known to yield to a low-intensity, continuously applied stretch force, as used in static stretching. Furthermore, a low-intensity, slowly applied, continuous, end-range static stretch does not appear to cause significant neuromuscular activation (evidence of increased EMG activity) of the stretched muscle.^24,108 However, the assertion that static stretching contributes to neuromuscular relaxation (inhibition) of the stretched muscle, as the result of activation of the GTO, is not supported by experimental evidence in human research studies.^24,98,138

Static Progressive Stretching

Static progressive stretching is a term that characterizes how static stretching is applied for maximum effectiveness. The shortened soft tissues are held in a comfortably lengthened position until a degree of relaxation is felt by the patient or therapist. Then the shortened tissues are incrementally lengthened even further and again held in the new end-range position for an additional duration of time.^17,80 This approach involves continuous displacement of a limb by varying the stretch force (stretch load) to capitalize on the stress-relaxation properties of soft tissue¹¹¹ (see Fig. 4.7 B).

Most studies that have explored the merits of static progressive stretching have examined the effectiveness of a dynamic orthosis (see Fig. 4.13), which allows the patient to control the degree of displacement of the limb.^17,80 Manual stretching and self-stretching procedures are also routinely applied in this manner.

Cyclic (Intermittent) Stretching

A relatively short-duration stretch force that is repeatedly but gradually applied, released, and then reapplied is described as a cyclic (intermittent) stretch.^{14,52,112,143} Cyclic stretching, by its very nature, is applied for multiple repetitions (stretch cycles) during a single treatment session. With cyclic stretching, the end-range stretch force is applied at a slow velocity, in a controlled manner, and at relatively low-intensity. For these reasons, cyclic stretching is not synonymous with ballistic stretching, which is characterized by high-velocity movements.

The differentiation between cyclic stretching and static stretching based on the duration that each stretch is applied is not clearly defined in the literature. According to some authors, in cyclic stretching, each cycle of stretch is held between 5 and 10 seconds.^52,143 However, investigators in other studies refer to stretching that involves 5- and 10-second stretch cycles as static stretching.^27,130 There is also no consensus on the optimal number of repetitions of cyclic stretching during a treatment session. Rather, this determination is often based on the patient's response to stretching.

Based on clinical experience, some therapists hold the opinion that appropriately applied, end-range cyclic stretching is as effective but more comfortable for a patient than a static stretch of comparable intensity, particularly if the static stretch is applied continuously for more than 30 seconds. There is some evidence to support this opinion. Although there have been few studies on cyclic or intermittent stretching (aside from those on ballistic stretching), cyclic loading has been shown to increase flexibility as effectively or more effectively than static stretching.^112,143

Speed of Stretch

Importance of a Slowly Applied Stretch

To minimize muscle activation during stretching and reduce the risk of injury to tissues and poststretch muscle soreness, the speed of stretch should be slow.^60,63,135 The stretch force should be applied and released gradually. A slowly applied stretch is less likely to increase tensile stresses on connective tissues^98,106,107 or to activate the stretch reflex. Remember, the Ia fibers of the muscle spindle are sensitive to the velocity of muscle lengthening. A slow rate stretch also affects the viscoelastic properties of connective tissue, making them more compliant. In addition, a stretch force applied at a low-velocity is easier for the therapist or patient to control and is, therefore, safer than a high-velocity stretch.

Ballistic Stretching

A rapid, forceful intermittent stretch—that is, a high-speed and high-intensity stretch—is commonly called ballistic stretching.^{1,7,8,48,135,173} It is characterized by the use of quick, bouncing movements that create momentum to carry the body segment through the ROM to stretch shortened structures. Although both static stretching and ballistic stretching have been shown to improve flexibility equally, ballistic stretching is thought to cause greater trauma to stretched tissues and greater residual muscle soreness than static stretching.¹⁶³

Consequently, although ballistic stretching has been shown to increase ROM safely in young, healthy subjects participating in a conditioning program,⁷¹ it is, for the most part, not recommended for elderly or sedentary individuals or patients with musculoskeletal pathology or chronic contractures. The rationale for this recommendation is³⁵:

• Tissues, weakened by immobilization or disuse, are easily injured.

• Dense connective tissue found in chronic contractures does not yield easily with high-intensity, short-duration stretch; rather, it becomes more brittle and tears more readily.

High-Velocity Stretching in Conditioning Programs and Advanced-Phase Rehabilitation

Although controversial, there are situations in which high-velocity stretching is appropriate for carefully selected individuals. For example, a highly trained athlete involved in a sport, such as gymnastics, that requires significant dynamic flexibility may need to incorporate high-velocity stretching in a conditioning program. Also, a young, active patient in the final phase of rehabilitation, who wishes to return to high-demand recreational or sport activities after a musculoskeletal injury, may need to perform carefully progressed, high-velocity stretching activities prior to beginning plyometric training or simulated, sport-specific exercises or drills.

If high-velocity stretching is employed, rapid, but low-load (low-intensity) stretches are recommended, paying close attention to effective stabilization. The following self-stretching progression is designed as a transition from static stretching to ballistic stretching to improve dynamic flexibility.¹⁷³

• Static stretching → Slow, short end-range stretching → Slow, full-range stretching → Fast, short end-range stretching → Fast, full-range stretching.

• The stretch force is initiated by having the individual actively contract the muscle group opposite the muscle and connective tissues to be stretched.

Frequency of Stretch

Frequency of stretching refers to the number of bouts (sessions) per day or per week a patient carries out a stretching regimen. The recommended frequency of stretching is based on the underlying cause of impaired mobility, the quality and level of healing of tissues, the chronicity and severity of a contracture, as well as a patient's age, use of corticosteroids, and previous response to stretching. Because few studies have attempted to determine the optimal frequency of stretching within a day or a week, it is not possible to draw evidence-based guidelines from the literature. As with decisions on the most appropriate number of repetitions of stretch in an exercise session, most suggestions are based on opinion. Frequency on a weekly basis ranges from two to five sessions, allowing time for rest between sessions for tissue healing and to minimize postexercise soreness. Ultimately, the decision is based on the clinical discretion of the therapist and the response and needs of the patient.

A therapist must be aware of any breakdown of tissues with repetitive stretch. A fine balance between collagen tissue breakdown and repair is needed to allow an increase in soft tissue lengthening. If there is excessive frequency of loading, tissue breakdown exceeds repair. Ultimately tissue failure is a possibility. In addition, if there is progressive loss of ROM over time rather than a gain in range, continued low-grade inflammation from repetitive stress can cause excessive collagen formation and hypertrophic scarring.

Mode of Stretch

The mode of stretch refers to the form of stretch or the manner in which stretching exercises are carried out. Mode of stretch can be defined by whom or what is applying the stretch force or whether the patient is actively participating in the stretching maneuver. Categories include, but are not limited to, manual and mechanical stretching or self-stretching as well as passive, assisted, or active stretching. Regardless of the form of stretching selected and implemented, it is imperative that the shortened muscle remains relaxed and that the restricted connective tissues yield as easily as possible to the stretch. To accomplish this, stretching procedures should be preceded by either low-intensity active exercise or therapeutic heat to warm up the tissues that are to be lengthened.

There is no best form or type of stretching. What is important is that the therapist and patient have many modes of stretching from which to choose. Box 4.6 lists some questions a therapist needs to answer to determine which forms of stretching are most appropriate and most effective for each patient at different stages of a rehabilitation program.

Manual Stretching

Characteristics. During manual stretching, a therapist or other trained practitioner or caregiver applies an external force to move the involved body segment slightly beyond the point of tissue resistance and available ROM. The therapist manually controls the site of stabilization as well as the direction, speed, intensity, and duration of stretch. As with ROM exercises (described in Chapter 3), manual stretching can be performed passively, with assistance from the patient, or even independently by the patient.

Manual stretching typically employs a controlled, end-range, static, progressive stretch applied at an intensity consistent with the patient's comfort level. It is held for 15 to 60 seconds and repeated for at least several repetitions.

Effectiveness. Despite widespread use of manual stretching in the clinical setting, its effectiveness for increasing the extensibility of range-limiting muscle-tendon units is debatable. Although some investigators ⁴⁴ have found that manual stretching increases muscle length and ROM in nonimpaired subjects, the short-duration of stretch that typically occurs with manual stretching may be why other investigators have reported a negligible effect from a manual stretching program,⁶⁶ especially in the presence of long-standing contractures associated with tissue pathology.⁹⁹

Application. The following are points to consider about the use of manual stretching.

• Manual stretching may be most appropriate in the early stages of a stretching program when a therapist wants to determine how a patient responds to varying intensities or durations of stretch and when optimal stabilization is most critical.

• Manual stretching performed passively is an appropriate choice for a therapist or caregiver if a patient cannot perform self-stretching owing to a lack of neuromuscular control of the body segment to be stretched.

• If a patient has control of the body segment to be stretched, it is often helpful to ask the patient to assist the therapist with the manual stretching maneuver, particularly if the patient is apprehensive about moving and is having difficulty relaxing. For example, if the patient concentrically contracts the muscle opposite the short muscle and assists with joint movement, the range-limiting muscle tends to relax reflexively, thus decreasing muscle tension interfering with elongation. This is one of several stretching procedures based on proprioceptive neuromuscular facilitation techniques that are discussed later in this chapter.

• Using procedures and hand placements similar to those described for self-ROM exercises (see Chapter 3), a patient can also independently lengthen range-limiting muscles and periarticular tissues with manual stretching. As such, this form of stretching is usually referred to as self-stretching and is discussed in more detail as the next topic in this section.

NOTE: Specific guidelines for the application of manual stretching, as well as descriptions and illustrations of manual stretching techniques for the extremities (Figures 4.16 through 4.36), are presented in later sections of this chapter.

Self-Stretching

Characteristics. Self-stretching (also referred to as flexibility exercises or active stretching) is a type of stretching procedure a patient carries out independently after careful instruction and supervised practice. Self-stretching enables a patient to maintain or increase the ROM gained as the result of direct intervention by a therapist. This form of stretching is often an integral component of a home exercise program and is necessary for long-term self-management of many musculoskeletal and neuromuscular disorders.

Effectiveness. Teaching a patient to carry out self-stretching procedures correctly and safely is fundamental for preventing re-injury or future dysfunction. Proper alignment of the body or body segments is critical for effective self-stretching. Sufficient stabilization of either the proximal or distal attachment of a shortened muscle is necessary but can be difficult to achieve with self-stretching. Every effort should be made to see that restricted structures are stretched specifically and that adjacent structures are not overstretched.

Application. The guidelines for the intensity, speed, duration, and frequency of stretch that apply to manual stretching are also appropriate for self-stretching procedures. Static stretching for a 30- to 60-second duration per repetition is considered the safest type of stretching for a self-stretching program.

Self-stretching exercises can be carried out in several ways.

• Using positions for self-ROM exercises described in Chapter 3, a patient can passively move the distal segment of a restricted joint with one or both hands to elongate a shortened muscle while stabilizing the proximal segment (Fig. 4.11 A).

• If the distal attachment of a shortened muscle is fixed (stabilized) on a support surface, body weight can be used as the source of the stretch force to elongate the shortened muscle-tendon unit (Fig. 4.11 B).

• Neuromuscular inhibition, using PNF stretching techniques, can be integrated into self-stretching procedures to promote relaxation in the muscle that is being elongated.

• Low-intensity active stretching (referred to by some as dynamic ROM⁸), using repeated, short-duration, end-range active muscle contractions of the muscle opposite the shortened muscle is another form of self-stretching exercise.^8,161,168

Mechanical Stretching

Characteristics. Mechanical stretching devices apply a very low-intensity stretch force (low-load) over a prolonged period of time to create relatively permanent lengthening of soft tissues, presumably due to plastic deformation.

There are many ways to use equipment to stretch shortened tissues and increase ROM. The equipment can be as simple as a cuff weight or weight-pulley system or as sophisticated as some adjustable orthotic devices or automated stretching machines.^{11,17,80,95,99,103,110,143} These mechanical stretching devices provide either a constant load with variable displacement or constant displacement with variable loads.

Effectiveness. Studies^17,80 about the efficacy of the two categories of mechanical loading devices base their effectiveness on the soft tissue properties of either creep or stress-relaxation, which occur within a short period of time, as well as plastic deformation, which occurs over an extended period of time.

Be cautious of studies or product information that report "permanent" lengthening as the result of use of mechanical stretching devices. The term, "permanent," may mean that length increases were maintained for as little as a few days or a week after use of a stretching device has been discontinued. Long-term follow-up may indicate that tissues have returned to their shortened state if the newly gained motion has not been used regularly in daily activities.

Application. It is often the responsibility of a therapist to recommend the type of stretching device that is most suitable and teach a patient how to safely use the equipment and monitor its use in the home setting. A therapist may also be involved in the fabrication of serial casts or splints.

Each of the following forms of mechanical stretching has been shown to be effective, particularly in reducing longstanding contractures.

• An effective stretch load applied with a cuff weight (Fig. 4.12) can be as low as a few pounds.⁹⁹

• Some devices, such as the Joint Active Systems" adjustable orthosis (Fig. 4.13), allow a patient to control and adjust the load (stretch force) during a stretching session.^17,80

• With other devices, the load is preset prior to the application of the splint, and the load remains constant while the splint is in place.

Duration of Mechanical Stretch

Mechanical stretching involves a substantially longer overall duration of stretch than is practical with manual stretching or self-stretching exercises. The duration of mechanical stretch reported in the literature ranges from 15 to 30 minutes to as long as 8 to 10 hours at a time^17,57,80 or continuous throughout the day except for time out of the device for hygiene and exercise.¹¹ Serial casts are worn for days or weeks at a time before being removed and then reapplied.⁷⁷ The time frame is dependent on the type of device employed, the cause, severity, and chronicity of impairment, and patient tolerance. The longer durations of stretch are required for patients with chronic contractures as the result of neurological or musculoskeletal disorders rather than healthy subjects with only mild hypomobility.^{17,77,80,99,103,111,116}

Proprioceptive Neuromuscular Facilitation Stretching Techniques

PNF stretching techniques,^{24,74,108,123,138} sometimes referred to as active stretching¹⁶⁸ or facilitative stretching,¹²⁵ integrate active muscle contractions into stretching maneuvers purportedly to inhibit or facilitate muscle activation and to increase the likelihood that the muscle to be lengthened remains as relaxed as possible as it is stretched.

The traditional explanation of the underlying mechanisms of PNF stretching is that reflexive relaxation occurrs during the stretching maneuvers, as the result of autogenic or reciprocal inhibition. In turn, inhibition leads to decreased tension in muscle fibers and, therefore, decreased resistance to elongation by the contractile elements of the muscle when stretched. However, this explanation has come into question in recent years.

Current thinking suggests that gains in ROM during or following PNF stretching techniques cannot be attributed solely to autogenic or reciprocal inhibition, which involves the spinal processing of proprioceptive information. Rather, increased ROM is the result of more complex mechanisms of sensorimotor processing, most likely combined with viscoelastic adaptation of the muscle-tendon unit and changes in a patient's tolerance to the stretching maneuver.^24,108,138

Regardless of the ongoing controversy about why PNF stretching techniques are effective, the results of numerous studies have demonstrated that the various PNF stretching techniques increase flexibility and ROM.^{8,38,52,123,135,168,170} However, the degree of neuromuscular relaxation associated with the PNF stretching maneuvers investigated was not determined in these studies. There is also evidence from some studies^108,135 that PNF stretching yields greater gains in ROM than static stretching, but there is no consensus on whether one PNF technique is significantly superior to another.

Types of PNF Stretching

There are several types of PNF stretching procedures, all of which have been shown to improve ROM VIDEO 4.1 . They include:

• Hold-relax (HR) or contract-relax (CR)

• Agonist contraction (AC)

• Hold-relax with agonist contraction (HR-AC).

With classic PNF, these techniques are performed with combined muscle groups acting in diagonal patterns^125,126,158 but have been modified in the clinical setting and in a number of studies and resources^{8,29,68,76,108,123,168} by stretching in a single plane or opposite the line of pull of a specific muscle group. (For a description of the PNF diagonal patterns, refer to Chapter 6.)

Hold-Relax and Contract-Relax

With the HR and CR procedures,29,76,108,123,125,126 the range-limiting target muscle is first lengthened to the point of tissue resistance or to the extent that is comfortable for the patient. The patient then performs a prestretch, end-range, isometric contraction (for about 5 seconds) followed by voluntary relaxation of the range-limiting target muscle. The limb is then passively moved into the new range as the range-limiting muscle is elongated. A sequence for using the HR and CR technique to stretch shortened pectoralis major muscles bilaterally and increase horizontal abduction of the shoulders is illustrated in Figure 4.14.

NOTE: Although the terms CR and HR often are used interchangeably, in classic PNF, the descriptions of the techniques are not identical. Both techniques are performed in diagonal patterns, but in the CR technique, the rotators of the limb are allowed to contract concentrically while all other muscle groups of the diagonal pattern contract isometrically during the prestretch phase of the procedure. In contrast, in the HR technique, the prestretch isometric contraction occurs in all muscles of the diagonal pattern.^126,158

Practitioners in the clinical and athletic training settings have reported that the HR and CR techniques appear to make passive elongation of muscles more comfortable for a patient than manual passive stretching.⁷⁶ A commonly held assumption is that neuromuscular relaxation, reflected by a decrease in EMG activity, possibly as the result of autogenic inhibition, occurs following the sustained, prestretch, isometric contraction of the muscle to be lengthened.^102,125,126 Some investigators^49,108 have challenged this assumption, attributing the gains in flexibility to the viscoelastic properties of the muscle-tendon unit. Their studies revealed evidence of a postcontraction sensory discharge (increased EMG activity) in the range-limiting muscle, suggesting that there was lingering tension in the muscle after the prestretch isometric contraction and that the range-limiting muscle was not reflexively relaxed prior to stretch. However the results of another study³⁰ indicated no evidence of a postcontraction elevation in EMG activity with the HR or CR techniques.

In light of the mixed evidence about the degree of neuro-muscular relaxation occurring, practitioners must determine the effectiveness of the HR or CR techniques based on the responses of their patients.

PRECAUTION: It is not necessary for the patient to perform a maximal isometric contraction of the range-limiting target muscle prior to stretch. Multiple repetitions of maximal prestretch isometric contractions have been shown to result in an acute increase in arterial blood pressure, most notably after the third repetition.³¹ To minimize the adverse effects of the Valsalva maneuver (elevation in blood pressure associated with a high-intensity effort), have the patient breathe regularly while performing submaximal (low-intensity) isometric contractions held for about 5 seconds with each repetition of the HR or CR procedure. From a practical perspective, a submaximal contraction is also easier for the therapist to control if the patient is strong.

Agonist Contraction

Another PNF stretching technique is the agonist contraction (AC) procedure. This term has been used by several authors^30,76,123 but can be misunderstood. The "agonist" refers to the muscle opposite the range-limiting target muscle. "Antagonist," therefore, refers to the range-limiting muscle. Think of it as the short muscle (the antagonist) preventing the full movement of the prime mover (the agonist). Dynamic range of motion (DROM)⁸ and active stretching¹⁶⁸ are other terms that have been used to describe the AC procedure.

To perform the AC procedure, the patient concentrically contracts (shortens) the muscle opposite the range-limiting muscle and then holds the end-range position for at least several seconds.^24,30,76,123 The movement of the limb is controlled independently by the patient and is deliberate and slow, not ballistic. In most instances, the shortening contraction is performed without the addition of resistance. For example, if the hip flexors are the range-limiting target muscle group, the patient performs end-range, prone leg lifts by contracting the hip extensors concentrically; the end-range contraction of the hip extensors is held for several seconds. After a brief rest period, the patient repeats the procedure.

Increased muscle length and joint ROM using the AC procedure have been reported. However, when the effectiveness of the AC technique has been compared to static stretching, the evidence is mixed.

In addition to the results of studies on the AC stretching procedure, clinicians have observed the following.

• The AC technique seems to be especially effective when significant muscle guarding restricts muscle lengthening and joint movement and is less effective in reducing chronic contractures.

• This technique is also useful when a patient cannot generate a strong, pain-free contraction of the range-limiting muscle, which must be done during the HR and CR procedures.

• This technique is also useful for initiating neuromuscular control in the newly gained range to re-establish dynamic flexibility.

• The AC technique is least effective if a patient has close to normal flexibility.

PRECAUTIONS: Avoid full-range, ballistic movements when performing concentric contractions of the agonist muscle group. Rest after each repetition to avoid muscle cramping when the agonist is contracting in a very shortened portion of its range.

Classic PNF theory suggests that when the agonist (the muscle opposite the range-limiting muscle) is activated and contracts concentrically, the antagonist (the range-limiting muscle) is reciprocally inhibited, allowing it to relax and lengthen more readily.^125,130 However, the theoretical mechanism of reciprocal inhibition has been substantiated only in animal studies.¹²⁷ Evidence of reciprocal inhibition during the AC procedure has not been demonstrated in human subjects^24,127,138 In fact, an increase of EMG activity, not reciprocal inhibition, has been identified in the range-limiting muscle during application of the AC stretching procedure.^30,123

Hold-Relax with Agonist Contraction

The HR-AC stretching technique combines the HR and AC procedures. The HR-AC technique is also referred to as the CR-AC procedure²⁴ or slow reversal hold-relax technique.¹⁵⁸ To perform the HR-AC procedure, move the limb to the point that tissue resistance is felt in the range-limiting target muscle; then have the patient perform a resisted, prestretch isometric contraction of the range-limiting muscle followed by voluntary relaxation of that muscle and an immediate concentric contraction of the muscle opposite the range-limiting muscle.^30,125,158

For example, to stretch knee flexors, extend the patient's knee to a comfortable, end-range position and then have the patient perform an isometric contraction of the knee flexors against resistance for about 5 seconds. Tell the patient to voluntarily relax and then actively extend the knee as far as possible, holding the newly gained range for several seconds.

PRECAUTIONS: Follow the same precautions as described for both the HR and AC procedures.

Integration of Function into Stretching

Importance of Strength and Muscle Endurance

As previously discussed, the strength of soft tissue is altered when it is immoblized for a period of time.^25,115 The magnitude of peak tension produced by muscle decreases, and the tensile strength of noncontractile tissues decreases. A muscle group that has been overstretched because its opposing muscle group has been in a shortened state for an extended period of time also becomes weak.^87,96,97 Therefore, it is critical to begin low-load resistance exercises to improve muscle performance (strength and endurance) as early as possible in a stretching program.

Initially, it is important to place emphasis on developing neuromuscular control and strength of the agonist, the muscle group opposite the muscle that is being stretched. For example, if the elbow flexors are the range-limiting muscle group, emphasize contraction of the elbow extensors in the gained range. Complement stretching the hamstrings to reduce a knee flexion contracture by using the quadriceps in the new range. Early use of the agonist enables the patient to elongate the hypomobile structures actively and use the recently gained ROM.

As ROM approaches a "normal" or functional level, the muscles that were shortened and then stretched must also be strengthened to maintain an appropriate balance of strength between agonists and antagonists throughout the ROM. Manual and mechanical resistance exercises are effective ways to load and strengthen muscles, but functional weight-bearing activities, such as those mentioned below also strengthen antigravity muscle groups.

Use of Increased Mobility for Functional Activities

As mentioned previously, gains in flexibility and ROM achieved as the result of a stretching program are transient, lasting only about 4 weeks after cessation of stretching.¹⁶⁶ The most effective means of achieving permanent increases in ROM and reducing functional limitations is to integrate functional activities into a stretching program to use the gained range on a regular basis. Use of functional activities to maintain mobility lends diversity and interest to a stretching program.

Active movements should be within the pain-free ROM. Examples of movements of the upper or lower extremities or spine that are components of daily activities include reaching, grasping, turning, twisting, bending, pushing, pulling, and squatting to name just a few. As soon as even small increases in tissue extensibility and ROM have been achieved, have the patient use the gained range by performing motions that simulate functional activities. Later, have the patient use all of the available ROM while actually doing specific functional tasks.

Functional movements that are practiced should complement the stretching program. For example, if a patient has been performing stretching exercises to increase shoulder mobility, have the patient fully use the available ROM by reaching as far as possible behind the back and overhead when grooming or dressing or by reaching for or placing objects on a high shelf (Fig. 4.15). Gradually increase the weight of objects placed on or removed from a shelf to strengthen shoulder musculature simultaneously.

If the focus of a stretching program has been to increase knee flexion after removal of a long-leg cast, emphasize flexing both knees before standing up from a chair or when stooping to pick up an object from the floor. These weight-bearing activities also strengthen the quadriceps that became weak while the leg was immobilized and the quadriceps were held in a shortened position.

The following guidelines are central to the development and implementation of stretching interventions. The results of an examination and evaluation of a patient's status determine the need for and types of stretching procedures that will be most effective in a patient's plan of care. This section identifies general guidelines to be addressed before, during, and after stretching procedures as well as guidelines specific to the application of manual stretching. Special considerations for teaching self-stretching exercises and using mechanical stretching devices are listed in Boxes 4.7 and 4.8.

Examination and Evaluation of the Patient

• Carefully review the patient's history and perform a thorough systems review.

• Select and perform appropriate tests and measurements. Determine the ROM available in involved and adjacent joints and if either active or passive mobility is impaired.

• Determine if hypomobility is related to other impairments of body structure or function and if it is causing activity limitations (functional limitations) or participation restrictions (disability).

• Ascertain if—and if so, which—soft tissues are the source of the impaired mobility. In particular, differentiate between joint capsule, periarticular, noncontractile tissue, and muscle length restrictions as the cause of limited ROM. Be sure to assess joint play and fascial mobility.

• Evaluate the irritability of the involved tissues and determine their stage of healing. When moving the patient's extremities or spine, pay close attention to the patient's reaction to movements. This not only helps identify the stage of healing of involved tissues, it helps determine the probable dosage (such as intensity and duration) of stretch that stays within the patient's comfort range.

• Assess the underlying strength of muscles in which there is limitation of motion and realistically consider the value of stretching the range-limiting structures. An individual must have the capability of developing adequate strength to control and use the new ROM safely.

• Be sure to determine what outcome goals (i.e., functional improvements) the patient is seeking to achieve as the result of the intervention program and determine if those goals are realistic.

• Analyze the impact of any factors that could adversely affect the projected outcomes of the stretching program.

Preparation for Stretching

• Review the goals and desired outcomes of the stretching program with the patient. Obtain the patient's consent to initiate treatment.

• Select the stretching techniques that will be most effective and efficient.

• Warm up the soft tissues to be stretched by the application of local heat or by active, low-intensity exercises. Warming up tight structures may increase their extensibility and may decrease the risk of injury from stretching.

• Have the patient assume a comfortable, stable position that allows the correct plane of motion for the stretching procedure. The direction of stretch is exactly opposite the direction of the joint or muscle restriction.

• Explain the procedure to the patient and be certain he or she understands.

• Free the area to be stretched of any restrictive clothing, bandages, or splints.

• Explain to the patient that it is important to be as relaxed as possible. Also, explain that the stretching procedures are geared to his or her tolerance level.

Application of Manual Stretching Procedures

• Move the extremity slowly through the free range to the point of tissue restriction.

• Grasp the areas proximal and distal to the joint in which motion is to occur. The grasp should be firm but not uncomfortable for the patient. Use padding, if necessary, in areas with minimal subcutaneous tissue, reduced sensation, or over a bony surface. Use the broad surfaces of your hands to apply all forces.

• Firmly stabilize the proximal segment (manually or with equipment) and move the distal segment.

• To stretch a multijoint muscle, stabilize either the proximal or distal segment to which the range-limiting muscle attaches. Stretch the muscle over one joint at a time and then over all joints simultaneously until the optimal length of soft tissues is achieved. To minimize compressive forces in small joints, stretch the distal joints first and proceed proximally.

• Consider incorporating a prestretch, isometric contraction of the range-limiting muscle (the hold-relax procedure) theoretically designed to relax the muscle reflexively prior to stretching it.

• To avoid joint compression during the stretching procedure, apply gentle (grade I) distraction to the moving joint.

• Apply a low-intensity stretch in a slow, sustained manner. Remember, the direction of the stretching movement is directly opposite the line of pull of the range-limiting muscle. Ask the patient to assist you with the stretch, or apply a passive stretch to lengthen the tissues. Take the hypomobile soft tissues to the point of firm tissue resistance and then move just beyond that point. The force must be enough to place tension on soft tissue structures but not so great as to cause pain or injure the structures. The patient should experience a pulling sensation, but not pain, in the structures being stretched. When stretching adhesions of a tendon within its sheath, the patient may experience a "stinging" sensation.

• Maintain the stretched position for 30 seconds or longer. During this time, the tension in the tissues should slowly decrease. When tension decreases, move the extremity or joint a little farther to progressively lengthen the hypomobile tissues.

• Gradually release the stretch force and allow the patient and therapist to rest momentarily while maintaining the range-limiting tissues in a comfortably elongated position. Then repeat the sequence several times.

• If the patient does not seem to tolerate a sustained stretch, use several very slow, gentle, intermittent stretches with the muscle in a lengthened position.

• If deemed appropriate, apply selected soft tissue mobilization procedures, such as fascial massage or cross-fiber friction massage, at or near the sites of adhesion during the stretching maneuver.

After Stretching

• Apply cold to the soft tissues that have been stretched and allow these structures to cool in a lengthened position. Cold may minimize poststretch muscle soreness that can occur as the result of microtrauma during stretching. When soft tissues are cooled in a lengthened position, increases in ROM are more readily maintained.^78,111

• Regardless of the type of stretching intervention used, have the patient perform active ROM and strengthening exercises through the gained range immediately after stretching. With your supervision and feedback, have the patient use the gained range by performing simulated functional movement patterns that are part of daily living, occupational, or recreational tasks.

• Develop a balance in strength in the antagonistic muscles in the new range, so there is adequate neuromuscular control and stability as flexibility increases.

There are a number of general precautions that apply to all forms of stretching interventions. In addition, some special precautions must be taken when advising patients about stretching exercises that are part of community-based fitness programs or commercially available exercise products marketed to the general public.

General Precautions

• Do not passively force a joint beyond its normal ROM. Remember, normal (typical) ROM varies among individuals. In adults, flexibility is greater in women than in men.¹⁷² When treating older adults, be aware of age-related changes in flexibility.

• Use extra caution in patients with known or suspected osteoporosis due to disease, prolonged bed rest, age, or prolonged use of steroids.

• Protect newly united fractures; be certain there is appropriate stabilization between the fracture site and the joint in which the motion takes place.

• Avoid vigorous stretching of muscles and connective tissues that have been immobilized for an extended period of time. Connective tissues, such as tendons and ligaments, lose their tensile strength after prolonged immobilization.⁹⁶ High-intensity, short-duration stretching procedures tend to cause more trauma and resulting weakness of soft tissues than low-intensity, long-duration stretch.

• Progress the dosage (intensity, duration, and frequency) of stretching interventions gradually to minimize soft tissue trauma and postexercise muscle soreness. If a patient experiences joint pain or muscle soreness lasting more than 24 hours after stretching, too much force has been used during stretching, causing an inflammatory response. This, in turn, causes increased scar tissue formation. Patients should experience no more residual discomfort than a transitory feeling of tenderness.

• Avoid stretching edematous tissue, as it is more susceptible to injury than normal tissue. Continued irritation of edematous tissue usually causes increased pain and edema.

• Avoid overstretching weak muscles, particularly those that support body structures in relation to gravity.

Special Precautions for Mass-Market Flexibility Programs

In an effort to develop and maintain a desired level of fitness, many people, young and old, participate in physical conditioning programs at home or in the community. Self-stretching exercises are an integral component of these programs. As a result, individuals frequently learn self-stretching procedures in fitness classes or from popular videos or television programs. Although much of the information in these resources is usually safe and accurate, there may be some errors and potential problems in flexibility programs designed for the mass market.

Common Errors and Potential Problems

Nonselective or poorly balanced stretching activities. General flexibility programs may include stretching regions of the body that are already mobile or even hypermobile but may neglect regions that are tight from faulty posture or inactivity. For example, in the sedentary population, some degree of hypomobility tends to develop in the hip flexors, trunk flexors, shoulder extensors and internal rotators, and scapular protractors from sitting in a slumped posture. Yet, many commercially available flexibility routines overemphasize exercises that stretch posterior muscle groups, already overstretched, and fail to include exercises to stretch the tight anterior structures. Consequently, faulty postures may worsen rather than improve.

Insufficient warm-up. Individuals involved in flexibility programs often fail to warm up prior to stretching.

Ineffective stabilization. Programs often lack effective methods of self-stabilization. Therefore, an exercise may fail to stretch the intended tight structures and may transfer the stretch force to structures that are already mobile or even hypermobile.

Use of ballistic stretching. Although a less common problem than in the past, some exercise routines still demonstrate stretches using ballistic maneuvers. Because this form of stretching is not well controlled, it increases the likelihood of postexercise muscle soreness and significant injury to soft tissues.

Excessive intensity. The phrase "no pain, no gain" is often used inappropriately as the guideline for intensity of stretch. An effective flexibility routine should be progressed gradually and should not cause pain or excessive stress to tissues.

Abnormal biomechanics. Some popular stretching exercises do not respect the biomechanics of the region. For example, the "hurdler's" stretch is designed to stretch unilaterally the hamstrings of one lower extremity and the quadriceps of the opposite extremity but imposes unsafe stresses on the medial capsule and ligaments of the flexed knee.

Insufficient information about age-related differences. One flexibility program does not fit all age groups. As a result of the normal aging process, mobility of connective tissues diminishes.^3,4,82 Consequently, elderly individuals, whose physical activity level has diminished with age, typically exhibit less flexibility than young adults. Even an adolescent after a growth spurt temporarily exhibits restricted flexibility, particularly in two-joint muscle groups. Flexibility programs marketed to the general public may not be sensitive to these normal, age-related differences in flexibility and may foster unrealistic expectations.

Strategies for Risk Reduction

• Whenever possible, assess the appropriateness and safety of exercises in a "prepackaged" flexibility program.

• If a patient you are treating is participating in a community-based fitness class, review the exercises in the program and determine their appropriateness and safety for your patient.

• Stay up-to-date on current exercise programs, products, and trends by monitoring the content and safety and your patient's use of home exercise videotapes.

• Determine whether a class or video is geared for individuals of the same age or with similar pathological conditions.

• Eliminate or modify those exercises that are inconsistent with the intervention plan you have developed for your patient.

• See that the flexibility program maintains a balance of mobility between antagonistic muscle groups and emphasizes stretching those muscle groups that often become shortened with age, faulty posture, or sedentary lifestyle.

• Teach your patient basic principles of self-stretching and how to apply those principles to select safe and appropriate stretching exercises and to avoid those that perpetuate impairments or have no value.

• Make sure your patient understands the importance of warming up prior to stretching. Give suggestions on how to warm up before stretching.

• Be certain that the patient knows how to provide effective self-stabilization to isolate stretch to specific muscle groups.

• Teach your patient how to determine the appropriate intensity of stretch; be sure your patient knows that, at most, postexercise muscle soreness should be mild and last no more than 24 hours.

Practitioners managing patients with structural or functional impairments, including chronic pain, muscle guarding or imbalances, and restricted mobility, may find it useful to integrate complementary therapies that address the body, mind, and spirit, such as relaxation training, Pilates exercises, yoga, or tai chi into a patient's plan of care to improve function and quality of life. Other interventions that are useful adjuncts to a stretching program include superficial or deep heat, cold, massage, biofeedback, and joint traction.

Complementary Exercise Approaches

Relaxation Training

Relaxation training, using methods of general relaxation (total body relaxation), has been used for many years by a variety of practitioners^{51,55,79,136,156,} to help patients learn to relieve or reduce pain, muscle tension, anxiety or stress, and associated physical impairments or medical conditions including tension headaches, high blood pressure, and respiratory distress. Volumes have been written by health professionals from many disciplines on topics such as chronic pain management, progressive relaxation, biofeedback, stress and anxiety management, and imagery. A brief overview of techniques is presented in this section.

There are a number of physiological, behavioral, cognitive, and emotional responses that occur during total body relaxation.¹⁵⁶ These key indicators are summarized in Box 4.9.

Common Elements of Relaxation Training

Relaxation training involves a reduction in muscle tension in the entire body or the region that is painful or restricted by using conscious effort and thought. Training occurs in a quiet environment with low lighting and soothing music or an auditory cue on which the patient may focus. The patient performs deep breathing exercises or visualizes a peaceful scene. When giving instructions, the therapist uses a soft tone of voice.

Examples of Approaches to Relaxation Training

Autogenic training. This approach, advocated by Schultz and Luthe¹³⁶ and Engle,⁵¹ involves conscious relaxation through autosuggestion and a progression of exercises as well as meditation.

Progressive relaxation. This technique, pioneered by Jacobson,⁷⁹ uses systematic, distal to proximal progression of voluntary contraction and relaxation of muscles. It is sometimes incorporated into childbirth education.

Awareness through movement. The system of therapy developed by Feldenkrais⁵⁵ combines sensory awareness, movements of the limbs and trunk, deep breathing, conscious relaxation procedures, and self-massage to alter muscle imbalances and abnormal postural alignment to remediate muscle tension and pain.

Sequence for Progressive Relaxation Techniques

• Place the patient in a quiet area and in a comfortable position, and be sure that restrictive clothing is loosened.

• Have the patient breathe in a deep, relaxed manner.

• Ask the patient to contract the distal musculature in the hands or feet voluntarily for several (5 to 7) seconds and then consciously relax those muscles for 20 to 30 seconds.

• Suggest that the patient try to feel a sense of heaviness in the hands or feet and a sense of warmth in the muscles just relaxed.

• Progress to a more proximal area of the body and have the patient actively contract and actively relax the more proximal musculature. Eventually have the patient isometrically contract and consciously relax the entire extremity.

• Suggest to the patient that he or she should feel a sense of relaxation and warmth throughout the entire limb and eventually throughout the whole body.

Pilates

Pilates is an approach to exercise that combines Western theories of biomechanics, core stability, and motor control with Eastern theories of the interaction of body, mind, and spirit.⁵ Components of a Pilates exercise session typically include deep breathing and core stabilization exercises, focus on activation and relaxation of specific muscle groups, posture control and awareness training, strength training (primarily using body weight as resistance), balance exercises, and flexibility exercises.¹⁴²

Although Pilates training often is part of community-based fitness programs for healthy adults, increasingly, therapists are incorporating elements of Pilates into individualized intervention programs for patients with a variety of diagnoses. Despite limited research, the effects and benefits of Pilates exercises on function (including improved flexiblity, strength, and pain control) and the quality of life in healthy individuals¹³⁷ and those with impairments are beginning to be documented.^86,134

Heat

Warming up prior to stretching is an important element of rehabilitation and fitness programs. It is well documented in human and animal studies that as intramuscular temperature increases, the extensibility of contractile and noncontractile soft tissues likewise increases. In addition, as the temperature of muscle increases, the amount of force required and the time the stretch force must be applied decrease.^{94,95,131,164} There is also a decrease in the rate of firing of the type II efferents from the muscle spindles and an increase in the sensitivity of the GTO, which makes it more likely to fire.⁵⁸ In turn, it is believed that when tissues relax and more easily lengthen, stretching is associated with less muscle guarding and is more comfortable for the patient.^94,95

Methods of Warm-Up

Superficial heat (hot packs, paraffin) or deep-heating modalities (ultrasound, shortwave diathermy) provide different mechanisms to heat tissues.^113,129 These thermal agents are used primarily to heat small areas such as individual joints, muscle groups, or tendons and may be applied prior to or during the stretching procedure.^6,47,89,131 There is no consensus as to whether heating modalities should be applied prior to or during the stretching procedure.

Low-intensity, active exercises, which generally increase circulation and core body temperature, also have been used as a mechanism to warm up large muscle groups prior to stretching.^44,61,89,141 Some common warm-up exercises are a brief walk, nonfatiguing cycling on a stationary bicycle, use of a stair-stepping machine, active heel raises, or a few minutes of active arm exercises.

Effectiveness of Warm-up Methods

The use of heat alone (a thermal agent or warm-up exercises) without stretching has been shown to have either little or no effect on improving muscle flexibility.^18,44,71,143 Although some evidence indicates that heat combined with stretching produces greater long-term gains in tissue length than stretching alone,^46,47 the results of other studies have shown comparable improvement in ROM with no significant differences between conditions.^{44,61,71,89,148}

Cold

The application of cold prior to stretching (cryostretching) compared to heat has been studied.^90,148 Advocates suggest its use to decrease muscle tone and make the muscle less sensitive during stretch in healthy subjects⁶⁷ and in patients with spasticity or rigidity secondary to upper motor neuron lesions.¹⁵⁸ The use of cold immediately after soft tissue injury effectively decreases pain and muscle spasm.⁹⁰ However, once soft tissue healing and scar formation begin, cold makes healing tissues less extensible and more susceptible to microtrauma during stretching.^35,94 Cooling soft tissues in a lengthened position after stretching has been shown to promote more lasting increases in soft tissue length and minimize poststretch muscle soreness.⁹⁵

Massage

Massage for Relaxation

Local muscle relaxation can be enhanced by massage, particularly with light or deep stroking techniques.^41,147 In some approaches to stress and anxiety or pain management, self-massage, using light stroking techniques (effleurage), is performed during the relaxation process.⁵⁵ In sports and conditioning programs,^10,147 massage has been used for general relaxation purposes or to enhance recovery after strenuous physical activity, although the efficacy of the latter is not well founded.¹⁵⁴ Because massage has been shown to increase circulation to muscles and decrease muscle spasm, it is a useful adjunct to stretching exercises.

Soft Tissue Mobilization/Manipulation Techniques

Another broad category of massage is soft tissue mobilization/ manipulation. Although these techniques involve various forms of deep massage, the primary purpose is not relaxation but rather, increasing the mobility of adherent or shortened connective tissues including fascia, tendons, and ligaments.²²

There are many techniques and explanations as to their effects on connective tissues, including the mechanical effects of stress and strain. Stresses are applied long enough for creep and stress-relaxation of tissues to occur. With myofascial massage,^22,100 stretch forces are applied across fascial planes or between muscle and septae. With friction massage,^37,75,147 deep circular or cross-fiber massage is applied to break up adhesions or minimize rough surfaces between tendons and their synovial sheaths. Friction massage is also used to increase the mobility of scar tissue in muscle as it heals. Theoretically, it applies stresses to scar tissue as it matures to align collagen fibers along the lines of stress for normal mobility. These forms of connective tissue massage as well as many other approaches and techniques of soft tissue mobilization are useful interventions for patients with restricted mobility.

Biofeedback

Biofeedback is another tool to help a patient learn and practice the process of relaxation. Biofeedback is also a useful means to help a patient learn how to activate a muscle, rather than relax it, such as when learning how to perform quadriceps setting exercises after knee surgery.

A patient, if properly trained, can electronically monitor and learn to reduce the amount of tension in muscles, as well as heart rate and blood pressure, through biofeedback instrumentation.^51,156 Through visual or auditory feedback, a patient can begin to sense or feel what muscle relaxation is. By reducing muscle tension, pain can be decreased and flexibility increased.

Joint Traction or Oscillation

Slight manual distraction of joint surfaces prior to or in conjunction with joint mobilization/manipulation techniques or stretching a muscle-tendon unit can be used to inhibit joint pain and spasm of muscles around a joint (see Chapter 5).^37,75,83 Pendular motions of a joint use the weight of the limb to distract the joint surfaces and simultaneously oscillate and relax the limb. The joint may be further distracted by adding a 1- or 2-lb weight to the extremity, which causes a stretch force on joint tissues.

As with the ROM exercises described in Chapter 3, the manual stretching techniques in this section are described with the patient in a supine position. Alternative patient positions, such as prone or sitting, are indicated for some motions and are noted when necessary. Manual stretching procedures in an aquatic environment are described in Chapter 9.

Effective manual stretching techniques require adequate stabilization of the patient and sufficient strength and good body mechanics of the therapist. Depending on the size (height and weight) of the therapist and the patient, modifications in the patient's position and suggested hand placements for stretching or stabilization may have to be made by the therapist.

Each description of a stretching technique is identified by the anatomical plane of motion that is to be increased followed by a notation of the muscle group being stretched. Limitations in functional ROM usually are caused by shortening of multiple muscle groups and periarticular structures, and they affect movement in combined (as well as anatomical) planes of motion. In this situation, however, stretching multiple muscle groups simultaneously using diagonal patterns (i.e., D₁ and D₂ flexion and extension of the upper or lower extremities as described in Chapter 6) is not recommended and, therefore, is not described in this chapter. The authors believe that combined, diagonal patterns are appropriate for maintaining available ROM with passive and active exercises and increasing strength in multiple muscle groups but are ineffective for isolating a stretch force to specific muscles or muscle groups of the extremities that are shortened and restricting ROM. Special considerations for each region being stretched are also noted in this section.

Prolonged passive stretching techniques using mechanical equipment are applied using the same points of stabilization as manual stretching. The stretch force is applied at a lower intensity and is applied over a much longer period than with manual stretching. The stretch force is provided by weights or splints rather than the strength or endurance of a therapist. The patient is stabilized with belts, straps, or counterweights.

NOTE: Manual stretching procedures for the musculature of the cervical, thoracic, and lumbar spine may be found in Chapter 16. Selected self-stretching techniques of the extremities and spine that a patient can do without assistance from a therapist are not described in this chapter. These exercises for each joint of the extremities can be found in Chapters 16,17,18,19,20,21,22.

Upper Extremity Stretching

The Shoulder: Special Considerations

Many muscles involved with shoulder motion attach to the scapula rather than the thorax. Therefore, when most muscles of the shoulder girdle are stretched, it is imperative to stabilize the scapula. Without scapular stabilization the stretch force is transmitted to the muscles that normally stabilize the scapula during movement of the arm. This subjects these muscles to possible overstretching and disguises the true ROM of the glenohumeral joint. Remember:

• When the scapula is stabilized and not allowed to abduct or upwardly rotate, only 120° of shoulder flexion and abduction can occur at the glenohumeral joint.

• The humerus must be externally rotated to gain full ROM of abduction.

• Muscles most apt to become shortened are those that prevent full shoulder flexion, abduction, and external rotation. It is rare to find restrictions in structures that prevent shoulder adduction and extension to neutral.

Shoulder Flexion

To increase flexion of the shoulder (stretch the shoulder extensors) (Fig. 4.16) VIDEO 4.2 .

Hand Placement and Procedure

• Grasp the posterior aspect of the distal humerus, just above the elbow.

• Stabilize the axillary border of the scapula to stretch the teres major, or stabilize the lateral aspect of the thorax and superior aspect of the pelvis to stretch the latissimus dorsi.

• Move the patient's arm into full shoulder flexion to elongate the shoulder extensors.

Shoulder Hyperextension

To increase hyperextension of the shoulder (stretch the shoulder flexors) (Fig. 4.17) VIDEO 4.3 .

Patient Position

Place the patient in a prone position.

Hand Placement and Procedure

• Support the forearm and grasp the distal humerus.

• Stabilize the posterior aspect of the scapula to prevent substitute movements.

• Move the patient's arm into full hyperextension of the shoulder to elongate the shoulder flexors.

Shoulder Abduction

To increase abduction of the shoulder (stretch the adductors) (Fig. 4.18).

Hand Placement and Procedure

• With the elbow flexed to 90°, grasp the distal humerus.

• Stabilize the axillary border of the scapula.

• Move the patient into full shoulder abduction to lengthen the adductors of the shoulder.

Shoulder Adduction

To increase adduction of the shoulder (stretch the abductors). It is rare when a patient is unable to adduct the shoulder fully to 0° (so the upper arm is at the patient's side). Even if a patient has worn an abduction splint after a soft tissue or joint injury of the shoulder, when he or she is upright the constant pull of gravity elongates the shoulder abductors so the patient can adduct to a neutral position.

Shoulder External Rotation

To increase external rotation of the shoulder (stretch the internal rotators) (Fig. 4.19) VIDEO 4.4 .

Hand Placement and Procedure

• Abduct the shoulder to a comfortable position—initially 30° or 45° and later to 90° if the glenohumoral (GH) joint is stable—or place the arm at the patient's side.

• Flex the elbow to 90° so the forearm can be used as a lever.

• Grasp the volar surface of the mid-forearm with one hand.

• Stabilization of the scapula is provided by the table on which the patient is lying.

• Externally rotate the patient's shoulder by moving the patient's forearm closer to the table. This fully lengthens the internal rotators.

PRECAUTION: Because it is necessary to apply the stretch forces across the intermediate elbow joint when elongating the internal and external rotators of the shoulder, be sure the elbow joint is stable and pain-free. In addition, keep the intensity of the stretch force very low, particularly in patients with osteoporosis.

Shoulder Internal Rotation

To increase internal rotation of the shoulder (stretch the external rotators) (Fig. 4.20).

Hand Placement and Procedure

• Abduct the shoulder to a comfortable position that allows internal rotation to occur without the thorax blocking the motion (initially to 45° and eventually to 90°).

• Flex the elbow to 90° so the forearm can be used as a lever.

• Grasp the dorsal surface of the midforearm with one hand, and stabilize the anterior aspect of the shoulder and support the elbow with your other forearm and hand.

• Move the patient's arm into internal rotation to lengthen the external rotators of the shoulder.

Shoulder Horizontal Abduction

To increase horizontal abduction of the shoulder (stretch the pectoralis muscles) (Fig. 4.21).

Patient Position

To reach full horizontal abduction in the supine position, the patient's shoulder must be at the edge of the table. Begin with the shoulder in 60° to 90° of abduction. The patient's elbow may also be flexed.

Hand Placement and Procedure

• Grasp the anterior aspect of the distal humerus.

• Stabilize the anterior aspect of the shoulder.

• Move the patient's arm below the edge of the table into full horizontal abduction to stretch the horizontal adductors.

NOTE: The horizontal adductors are usually tight bilaterally. Stretching techniques can be applied bilaterally by the therapist, or a bilateral self-stretch can be done by the patient by using a corner or wand (see Figs. 17.30,17.31,17.32).

Scapular Mobility

To have full shoulder motion, a patient must have normal scapular mobility. (See scapular mobilization/manipulation techniques in Chapter 5.)

The Elbow and Forearm: Special Considerations

Several muscles that cross the elbow, such as the biceps brachii and brachioradialis, also influence supination and pronation of the forearm. Therefore, when stretching the elbow flexors and extensors, the techniques should be performed with the forearm pronated as well as supinated.

Elbow Flexion

To increase elbow flexion (stretch the one-joint elbow extensors).

Hand Placement and Procedure

• Grasp the distal forearm just proximal to the wrist.

• With the arm at the patient's side supported on the table, stabilize the proximal humerus.

• Flex the patient's elbow just past the point of tissue resistance to lengthen the elbow extensors.

To increase elbow flexion with the shoulder flexed (stretch the long head of the triceps) (Fig. 4.22).

Patient Position, Hand Placement, and Procedure

• With the patient sitting or lying supine with the arm at the edge of the table, flex the patient's shoulder as far as possible.

• While maintaining shoulder flexion, grasp the distal forearm and flex the elbow as far as possible.

Elbow Extension

To increase elbow extension (stretch the elbow flexors) (Fig. 4.23) VIDEO 4.5 .

Hand Placement and Procedure

• Grasp the distal forearm.

• With the upper arm at the patient's side supported on the table, stabilize the scapula and anterior aspect of the proximal humerus.

• Extend the elbow just past the point of tissue resistance to lengthen the elbow flexors.

NOTE: Be sure to do this with the forearm in supination, pronation, and neutral position to stretch each of the elbow flexors.

To increase elbow extension with the shoulder extended (stretch the long head of the biceps).

Patient Position, Hand Placement, and Procedure

• With the patient lying supine close to the side of the table, stabilize the anterior aspect of the shoulder, or with the patient lying prone, stabilize the scapula.

• Pronate the forearm, extend the elbow, and then extend the shoulder.

PRECAUTION: It has been reported that heterotopic ossification (the appearance of ectopic bone in the soft tissues around a joint) can develop around the elbow after traumatic or burn injuries.⁵⁰ It is believed that vigorous, forcible passive stretching of the elbow flexors may increase the risk of this condition developing. Passive or assisted stretching, therefore, should be applied very gently and gradually in the elbow region. Use of active stretching, such as agonist contraction, might also be considered.

Forearm Supination or Pronation

To increase supination or pronation of the forearm.

Hand Placement and Procedure

• With the patient's humerus supported on the table and the elbow flexed to 90°, grasp the distal forearm.

• Stabilize the humerus.

• Supinate or pronate the forearm just beyond the point of tissue resistance.

• Be sure the stretch force is applied to the radius rotating around the ulna. Do not twist the hand, thereby avoiding stress to the wrist articulations.

• Repeat the procedure with the elbow extended. Be sure to stabilize the humerus to prevent internal or external rotation of the shoulder.

The Wrist and Hand: Special Considerations

The extrinsic muscles of the fingers cross the wrist joint and, therefore, may influence the ROM of the wrist VIDEO 4.6 . Wrist motion may also be influenced by the position of the elbow and forearm, because the wrist flexors and extensors attach proximally on the epicondyles of the humerus.

When stretching the musculature of the wrist, the stretch force should be applied proximal to the metacarpophalangeal (MCP) joints, and the fingers should be relaxed.

Patient Position

When stretching the muscles of the wrist and hand, have the patient sit in a chair adjacent to you with the forearm supported on a table to stabilize the forearm effectively.

Wrist Flexion

To increase wrist flexion.

Hand Placement and Procedure

• The forearm may be supinated, in midposition, or pronated.

• Stabilize the forearm against the table and grasp the dorsal aspect of the patient's hand.

• To elongate the wrist extensors, flex the patient's wrist and allow the fingers to extend passively.

• To further elongate the wrist extensors, extend the patient's elbow.

Wrist Extension

To increase wrist extension (Fig. 4.24).

Hand Placement and Procedure

• Pronate the forearm or place it in midposition, and grasp the patient at the palmar aspect of the hand. If there is a severe wrist flexion contracture, it may be necessary to place the patient's hand over the edge of the treatment table.

• Stabilize the forearm against the table.

• To lengthen the wrist flexors, extend the patient's wrist, allowing the fingers to flex passively.

Radial Deviation

To increase radial deviation.

Hand Placement and Procedure

• Grasp the ulnar aspect of the hand along the fifth metacarpal.

• Hold the wrist in midposition.

• Stabilize the forearm.

• Radially deviate the wrist to lengthen the ulnar deviators of the wrist.

Ulnar Deviation

To increase ulnar deviation.

Hand Placement and Procedure

• Grasp the radial aspect of the hand along the second metacarpal, not the thumb.

• Stabilize the forearm.

• Ulnarly deviate the wrist to lengthen the radial deviators.

The Digits: Special Considerations

The complexity of the relationships among the joint structures and the intrinsic and multijoint extrinsic muscles of the digits requires careful examination and evaluation of the factors that contribute to loss of function in the hand because of limitation of motion VIDEO 4.7 . The therapist must determine if a limitation is from restriction of joints, decreased extensibility of the muscle-tendon unit, or adhesions of tendons or ligaments. The digits should always be stretched individually, not simultaneously. If an extrinsic muscle limits motion, lengthen it over one joint while stabilizing the other joints. Then, hold the lengthened position and stretch it over the second joint, and so forth, until normal length is obtained. As noted in Chapter 3, begin the motion with the most distal joint to minimize shearing and compressive stresses to the surfaces of the small joints of the digits. Specific interventions to manage adhesions of tendons are described in Chapter 19.

CMC Joint of the Thumb

To increase flexion, extension, abduction, or adduction of the carpometacarpal (CMC) joint of the thumb.

Hand Placement and Procedure

• Stabilize the trapezium with your thumb and index finger.

• Grasp the first metacarpal (not the first phalanx) with your other thumb and index finger.

• Move the first metacarpal in the desired direction to increase CMC flexion, extension, abduction, and adduction.

MCP Joints of the Digits

To increase flexion, extension, abduction, or adduction of the MCP joints of the digits.

Hand Placement and Procedure

• Stabilize the metacarpal with your thumb and index finger.

• Grasp the proximal phalanx with your other thumb and index finger.

• Keep the wrist in midposition.

• Move the MCP joint in the desired direction for stretch.

• Allow the interphalangeal (IP) joints to flex or extend passively.

PIP and DIP Joints

To increase flexion or extension of the proximal and distal interphalangeal (PIP and DIP) joints.

Hand Placement and Procedure

• Grasp the middle or distal phalanx with your thumb and finger.

• Stabilize the proximal or middle phalanx with your other thumb and finger.

• Move the PIP or DIP joint in the desired direction for stretch.

Stretching Specific Extrinsic and Intrinsic Muscles of the Fingers

Elongation of extrinsic and intrinsic muscles of the hand is described in Chapter 3. To stretch these muscles beyond their available range, the same hand placement and stabilization are used as with passive ROM. The only difference in technique is that the therapist moves each segment into the stretch range.

Lower Extremity Stretching

The Hip: Special Considerations

Because muscles of the hip attach to the pelvis or lumbar spine, the pelvis must always be stabilized when lengthening muscles about the hip VIDEO 4.8 . If the pelvis is not stabilized, the stretch force is transferred to the lumbar spine, in which unwanted compensatory motion then occurs.

Hip Flexion

To increase flexion of the hip with the knee flexed (stretch the gluteus maximus).

Hand Placement and Procedure

• Flex the hip and knee simultaneously.

• Stabilize the opposite femur in extension to prevent posterior tilt of the pelvis.

• Move the patient's hip and knee into full flexion to lengthen the one-joint hip extensor.

Hip Flexion with Knee Extension

To increase flexion of the hip with the knee extended (stretch the hamstrings) (Fig. 4.25 A and B).

Hand Placement and Procedure

• With the patient's knee fully extended, support the patient's lower leg with your arm or shoulder.

• Stabilize the opposite extremity along the anterior aspect of the thigh with your other hand or a belt or with the assistance of another person.

• With the knee at 0° extension and the hip in neutral rotation, flex the hip as far as possible.

NOTE: Externally rotate the hip prior to hip flexion to isolate the stretch force to the medial hamstrings and internally rotate the hip to isolate the stretch force to the lateral hamstrings.

Alternative Therapist Position

Kneel on the mat and place the patient's heel or distal tibia against your shoulder (see Fig. 4.25 B). Place both of your hands along the anterior aspect of the distal thigh to keep the knee extended. The opposite extremity is stabilized in extension by a belt or towel around the distal thigh and held in place by the therapist's knee.

Hip Extension

To increase hip extension (stretch the iliopsoas) (Fig. 4.26) VIDEO 4.9 .

Patient Position

Have the patient positioned close to the edge of the treatment table so the hip being stretched can be extended beyond neutral. The opposite hip and knee are flexed toward the patient's chest to stabilize the pelvis and spine.

Hand Placement and Procedure

• Stabilize the opposite leg against the patient's chest with one hand, or if possible, have the patient assist by grasping around the thigh and holding it to the chest to prevent an anterior tilt of the pelvis during stretching.

• Move the hip to be stretched into extension or hyperextension by placing downward pressure on the anterior aspect of the distal thigh with your other hand. Allow the knee to extend so the two-joint rectus femoris does not restrict the range.

Alternate Position

The patient can lie prone (Fig. 4.27).

Hand Placement and Procedure

• Support and grasp the anterior aspect of the patient's distal femur.

• Stabilize the patient's buttocks to prevent movement of the pelvis.

• Extend the patient's hip by lifting the femur off the table.

Hip Extension with Knee Flexion

To increase hip extension and knee flexion simultaneously (stretch the rectus femoris).

Patient Position

Use either of the positions previously described for increasing hip extension in the supine or prone positions (see Figs. 4.26 and 4.27).

Hand Placement and Procedure

• With the hip held in full extension on the side to be stretched, move your hand to the distal tibia and gently flex the knee of that extremity as far as possible.

• Do not allow the hip to abduct or rotate.

Hip Abduction

To increase abduction of the hip (stretch the adductors) (Fig. 4.28) VIDEO 4.10 .

Hand Placement and Procedure

• Support the distal thigh with your arm and forearm.

• Stabilize the pelvis by placing pressure on the opposite anterior iliac crest or by maintaining the opposite lower extremity in slight abduction.

• Abduct the hip as far as possible to stretch the adductors.

NOTE: You may apply your stretch force cautiously at the medial malleolus only if the knee is stable and pain-free. This creates a great deal of stress to the medial supporting structures of the knee and is generally not recommended by the authors.

Hip Adduction

To increase adduction of the hip (stretch the tensor fasciae latae and iliotibial [IT] band) (Fig. 4.29) VIDEO 4.11 .

Patient Position

Place the patient in a side-lying position with the hip to be stretched uppermost. Flex the bottom hip and knee to stabilize the patient.

Hand Placement and Procedure

• Stabilize the pelvis at the iliac crest with your proximal hand.

• Flex the knee and extend the patient's hip to neutral or into slight hyperextension, if possible.

• Let the patient's hip adduct with gravity and apply an additional stretch force with your other hand to the lateral aspect of the distal femur to further adduct the hip.

NOTE: If the patient's hip cannot be extended to neutral, the hip flexors must be stretched before the tensor fasciae latae can be stretched.

Hip External Rotation

To increase external rotation of the hip (stretch the internal rotators) (Fig. 4.30 A).

Patient Position

Place the patient in a prone position, hips extended and knee flexed to 90°.

Hand Placement and Procedure

• Grasp the distal tibia of the extremity to be stretched.

• Stabilize the pelvis by applying pressure with your other hand across the buttocks.

• Apply pressure to the lateral malleolus or lateral aspect of the tibia, and externally rotate the hip as far as possible.

Alternate Position and Procedure

Sitting at the edge of a table with hips and knees flexed to 90°:

• Stabilize the pelvis by applying pressure to the iliac crest with one hand.

• Apply the stretch force to the lateral malleolus or lateral aspect of the lower leg, and externally rotate the hip.

NOTE: When you apply the stretch force against the lower leg in this manner, thus crossing the knee joint, the knee must be stable and pain-free. If the knee is not stable, it is possible to apply the stretch force by grasping the distal thigh, but the leverage is poor and there is a tendency to twist the skin.

Hip Internal Rotation

To increase internal rotation of the hip (stretch the external rotators) (Fig. 4.30 B).

Patient Position and Stabilization

Position the patient the same as when increasing external rotation, described previously.

Hand Placement and Procedure

Apply pressure to the medial malleolus or medial aspect of the tibia, and internally rotate the hip as far as possible.

The Knee: Special Considerations

The position of the hip during stretching influences the flexibility of the flexors and extensors of the knee VIDEO 4.12 . The flexibility of the hamstrings and the rectus femoris must be examined and evaluated separately from the one-joint muscles that affect knee motion.

Knee Flexion

To increase knee flexion (stretch the knee extensors) (Fig. 4.31).

Patient Position

Have the patient assume a prone position.

Hand Placement and Procedure

• Stabilize the pelvis by applying downward pressure across the buttocks.

• Grasp the anterior aspect of the distal tibia, and flex the patient's knee.

PRECAUTION: Place a rolled towel under the thigh just above the knee to prevent compression of the patella against the table during the stretch. Stretching the knee extensors too vigorously in the prone position can traumatize the knee joint and cause swelling.

Alternate Position and Procedure

• Have the patient sit with the thigh supported on the treatment table and leg flexed over the edge as far as possible.

• Stabilize the anterior aspect of the proximal femur with one hand.

• Apply the stretch force to the anterior aspect of the distal tibia and flex the patient's knee as far as possible.

NOTE: This position is useful when working in the 0° to 100° range of knee flexion. The prone position is best for increasing knee flexion from 90° to 135°.

Knee Extension

To increase knee extension in the midrange (stretch the knee flexors) (Fig. 4.32).

Patient Position

Place the patient in a prone position and put a small, rolled towel under the patient's distal femur, just above the patella.

Hand Placement and Procedure

• Grasp the distal tibia with one hand and stabilize the buttocks to prevent hip flexion with the other hand.

• Slowly extend the knee to stretch the knee flexors.

End-Range Knee Extension

To increase end-range knee extension (Fig. 4.33) VIDEO 4.13 .

Patient Position

Patient assumes a supine position.

Hand Placement and Procedure

• Grasp the distal tibia of the knee to be stretched.

• Stabilize the hip by placing your hand or forearm across the anterior thigh. This prevents hip flexion during stretching.

• Apply the stretch force to the posterior aspect of the distal tibia, and extend the patient's knee.

The Ankle and Foot: Special Considerations

The ankle and foot are composed of multiple joints VIDEO 4.14 . Consider the mobility of these joints (see Chapter 5) as well as the multijoint muscles that cross these joints when increasing ROM of the ankle and foot.

Ankle Dorsiflexion

To increase dorsiflexion of the ankle with the knee extended (stretch the gastrocnemius muscle) (Fig. 4.34).

Hand Placement and Procedure

• Grasp the patient's heel (calcaneus) with one hand, maintain the subtalar joint in a neutral position, and place your forearm along the plantar surface of the foot.

• Stabilize the anterior aspect of the tibia with your other hand.

• Dorsiflex the talocrural joint of the ankle by pulling the calcaneus in an inferior direction with your thumb and fingers while gently applying pressure in a superior direction just proximal to the heads of the metatarsals with your forearm.

To increase dorsiflexion of the ankle with the knee flexed (stretch the soleus muscle). The knee must be flexed to eliminate the effect of the two-joint gastrocnemius muscle. Hand placement, stabilization, and stretch force are the same as when stretching the gastrocnemius.

PRECAUTION: When stretching the gastrocnemius or soleus muscles, avoid placing too much pressure against the heads of the metatarsals and stretching the long arch of the foot. Overstretching the long arch of the foot can cause a flat foot or a rocker-bottom foot.

Ankle Plantarflexion

To increase plantarflexion of the ankle.

Hand Placement and Procedure

• Support the posterior aspect of the distal tibia with one hand.

• Grasp the foot along the tarsal and metatarsal areas.

• Apply the stretch force to the anterior aspect of the foot, and plantarflex the foot as far as possible.

Ankle Inversion and Eversion

To increase inversion and eversion of the ankle. Inversion and eversion of the ankle occur at the subtalar joint as a component of pronation and supination. Mobility of the subtalar joint (with appropriate strength) is particularly important for walking on uneven surfaces.

Hand Placement and Procedure

• Stabilize the talus by grasping just distal to the malleoli with one hand.

• Grasp the calcaneus with your other hand, and move it medially and laterally at the subtalar joint.

Stretching Specific Muscles of the Ankle and Foot

Hand Placement and Procedure

• Stabilize the distal tibia with your proximal hand.

• Grasp around the foot with your other hand and align the motion and force opposite the line of pull of the tendons. Apply the stretch force against the bone to which the muscle attaches distally.

  • To stretch the tibialis anterior (which inverts and dorsi-flexes the ankle): Grasp the dorsal aspect of the foot across the tarsals and metatarsals and plantarflex and abduct the foot.

  • To stretch the tibialis posterior (which plantarflexes and inverts the foot): Grasp the plantar surface of the foot around the tarsals and metatarsals and dorsiflex and abduct the foot.

  • To stretch the peroneals (which evert the foot): Grasp the lateral aspect of the foot at the tarsals and metatarsals and invert the foot.

Toe Flexion and Extension

To increase flexion and extension of the toes: It is best to stretch any musculature that limits motion in the toes individually. With one hand, stabilize the bone proximal to the restricted joint, and with the other hand, move the phalanx in the desired direction.

Neck and Trunk

Stretching techniques to increase mobility in the cervical, thoracic, and lumbar spine may be found in Chapter 16.

Self-Stretching Techniques

Examples of self-stretching techniques, performed independently by the patient after appropriate instruction, may be found in Chapters 17 through 22 (upper and lower extremities) and Chapter 16 (neck and trunk).

Critical Thinking and Discussion

1. What physical findings from an examination of a patient would lead you to decide that stretching exercises were an appropriate intervention?

2. Discuss the advantages and disadvantages of various stretching exercises, specifically manual stretching, self-stretching, and mechanical stretching. Under what circumstances would one form be a more appropriate choice than another?

3. Discuss how the effectiveness of a program of stretching activities is influenced by the responses of contractile and noncontractile soft tissues to stretch. Consider such factors as intensity, speed, duration, and frequency of stretch.

4. Discuss how your approach to and application of stretching would differ when developing stretching exercises for a healthy young adult with limited mobility in the (a) shoulder, (b) knee, or (c) ankle in contrast to an elderly individual with osteoporosis and limited motion in the same regions.

5. Explain the procedures for and rationale behind each of the following types of neuromuscular inhibition: HR, HR-AC, CR, and AC. Under what circumstances would you choose one technique over another?

6. Select a popular exercise videotape. Review and critique the flexibility exercises on the tape. Was there a balance in the flexibility exercises in the program? Were the exercises executed safely and correctly? Were the exercises appropriate for the target population?

7. Your patient has been attending Pilates classes over the past few months, but is now receiving your therapy services for management of a chronic strain of the hamstrings. How could you integrate your patient's participation in these classes with your plan of care?

Laboratory Practice

1. Manually stretch as many major muscle groups of the upper and lower extremities as is safe and practical with the patient in prone-lying, side-lying, or seated positions.

2. While considering individual muscle actions and lines of pull, demonstrate how to specifically and fully elongate the following muscles: pectoralis major, biceps brachii, brachioradialis, brachialis, triceps, extensor or flexor carpi ulnaris or radialis, flexor digitorum superficialis or pro-fundus, rectus femoris versus the iliopsoas, gastrocnemius versus soleus, and the tibialis anterior and posterior.

3. Teach your partner how to stretch major muscle groups of the upper and lower extremities using either body weight or a cuff weight as the stretch force. Be sure to include effective stabilization procedures for these stretching techniques whenever possible.

4. Using either the hold-relax or contract-relax and the hold-relax agonist contraction PNF stretching techniques, elongate at least two major muscle groups at the shoulder, elbow, wrist, hip, knee, and ankle. Be sure to position, align, and stabilize your partner properly.

5. Design an effective and efficient series of self-stretching exercises that a person who works at a desk most of the day could incorporate into a daily home fitness routine. Demonstrate and teach each self-stretching exercise to your laboratory partner.

6. Identify a recreational/sport activity that your partner enjoys (i.e., tennis, golf, cycling, jogging, etc.) and design and demonstrate a program of self-stretching exercises to prepare your partner for the activity and reduce the risk of injury.

7. Design a program of progressive relaxation exercises for total body relaxation. Then, implement the relaxation training sequence with your partner.