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“When health is absent Wisdom cannot reveal itself, Art cannot become manifest, Strength cannot be exerted, Wealth is useless and Reason is powerless.”

Herophilos (300 B.C.)


On completion of this chapter, the student/practitioner will be able to:

  • Discuss the role of physical agents in patient intervention.

  • List the physical agents available to the practicing therapist and note their therapeutic indications.

  • Describe the various forms of therapeutic electrical stimulation.

  • Develop evidence-based knowledge of the indications, contraindications, and applications of physical agents.

Key Terms

  • Electrical stimulation

  • Modality

  • Pain modulation

  • Physical agents


The inherent potential of the peripheral nervous system to undergo autogenic repair after injury or insult is a compelling impetus both to individuals experiencing damage or loss of function and to the practitioners addressing the associated symptoms and impairments. Although it is known that injured peripheral axons have the ability to regenerate, restoration of functional ability remains less than optimal. Nevertheless, pursuit of effective and meaningful recovery remains paramount.

Physical agents, or therapeutic modalities, represent a spectrum of adjunctive therapies used to complement or supplement other interventions, such as exercise, joint or tissue mobilization, strengthening, or stretching. Collectively, physical agents and the interventions they supplement comprise the more comprehensive intervention plan. Advances in understanding of the biophysical effects of physical agents have spurred their continued use in rehabilitation.16 Although injured peripheral nerves have demonstrated the ability to regenerate, physical agents impart specific and selective responses to mediate tissue healing that have led practitioners to select physical agents for peripheral nerve injury (PNI) intervention.7

Physical Agents

Role of Physical Agents

Physical agents are complementary, or adjunctive, interventions used with other treatment strategies to increase the probability that a desired therapeutic effect will be realized. For example, the use of electrical stimulation (ES) at a wound bed may be used to attract cells, such as fibroblasts, or influence the orientation of endothelial cells to promote and potentiate wound healing.1,8,9 Physical agents are not intended to supplant more skilled and selective interventions provided by practitioners. Rather, physical agents represent a viable supplementary class of tools for influencing healing of injured tissue.

What Are Physical Agents?

Physical agents are means of delivering and using for therapeutic purpose one or more of several types of physical energies. Therapeutic benefits are derived from the transfer of these energies to patients to stimulate tissue responses that may not be realized through other interventions. Physical agents traditionally include thermal modalities (e.g., heat and cold), electromagnetic modalities (e.g., ES and diathermy), light modalities (e.g., laser or infrared), and mechanical modalities (e.g., traction, compression, and ultrasound [US]). Table 17-1 summarizes the classes and types of ...

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