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Muscle performance is the capacity of a muscle to do work (force × distance).10 Despite this simple definition, muscle performance is a complex component of functional movement and is influenced by all the body systems. Factors that affect muscle performance include the muscle morphology and physiology; neurological, biochemical, and biomechanical influences; and metabolic, cardiovascular, respiratory, cognitive, and emotional function. A healthy and fully functioning muscular system is critical for meeting the physical demands imposed on the body and for allowing individuals to be mobile, recreate, work, and pursue meaningful experiences.

The key elements of muscle performance are strength, power, and endurance.10 If any one or more of these elements is impaired, activity limitations and participation restrictions or increased risk of mobility deficits may ensue. Factors such as injury, disease, immobilization, disuse, and inactivity may impair muscle performance, leading to weakness and muscle atrophy. When deficits in muscle performance are present, resistance exercises are an appropriate therapeutic intervention.

Resistance exercise is an activity in which dynamic or static muscle contraction is resisted by an outside force applied manually or mechanically.91,236 Resistance exercise, also referred to as resistance training,7,8,159 is an essential element of rehabilitation programs for persons with impaired muscle performance. In addition, resistance exercise is an integral component of conditioning programs for those who wish to promote or maintain health and physical well-being, enhance performance of motor skills, and reduce the risk of injury and disease.7,8,230

A comprehensive examination and evaluation of the patient or client help a therapist determine whether a program of resistance exercise is warranted and likely to be effective. Many factors will influence this decision and help determine how the exercises are designed, implemented, and progressed. Factors to be considered include the underlying pathology; the extent and severity of muscle performance impairments; the presence of other deficits; the stage of tissue healing after injury or surgery; and the patient’s or client’s age, overall level of fitness, and ability to cooperate and learn. Once a resistance exercise program is developed and prescribed, the therapist should either implement the program directly or teach and supervise the exercise before transitioning to an independent, home-based program.

This chapter provides information on resistance exercise, identifies the determinants of resistance training programs, summarizes the principles and guidelines for application of manual and mechanical resistance exercise, and explores a variety of regimens for resistance training. It also addresses the available scientific evidence on the relationship between improvements in muscle performance and enhanced functional abilities. The specific techniques described and illustrated in this chapter focus on manual resistance exercise for the extremities, primarily used during the early phase of rehabilitation. Additional exercises performed independently by the patient or client using resistance equipment are described and illustrated in Chapters 16, 17, 18, 19, 20, ...

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