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Introduction

This chapter describes the therapeutic objectives, methods, and effects of a therapeutic electrical current applied to the human body.

• The primary effects of electrotherapy are the result of the depolarization of sensory, motor, or pain nerves. Other effects are caused by electrochemical changes in the tissue and any resulting muscle contraction. Chapter 12 describes the different electrical parameters that can be applied and modified, each type of current producing unique effects within the tissues and causing a wide range of therapeutic responses (Table 12-1).

TABLE 12-1Therapeutic Uses of Electrical Currents

The type of current, the current's parameters (intensity, phase duration, and pulse frequency), and the electrode size and arrangement can produce specific physiological events and target specific tissues. Electrical stimulation has little, if any, direct effect on the cellular-level inflammation response, but this does not imply that it does not have a useful role in injury management.

The Body Circuit

The human body is a mass of tissues and fluids, each having varying ability to conduct an electrical current based on its water content. As the percentage of the water in tissue increases, its ability to transmit electricity increases.

Tissues are either excitable or nonexcitable. Excitable tissues such as nerves, muscle fibers, and cell membranes are influenced directly by the electrical current. Nonexcitable tissues such as bone, cartilage, tendons, adipose tissue, and ligaments do not directly respond to current flow but may be indirectly influenced by the electrical fields caused by the current (Fig. 12-1).

Figure 12-1.

Flow of Therapeutic Electrical Current. At the skin-electrode interface the flow of electrons is exchanged for the flow of ions within the body. Within the tissues, the current has multiple paths from which to choose. Positively charged ions move toward the cathode (–) and away from the anode (+). Negatively charged ions move toward the anode (+) and away from the cathode (−).

The outer layer of the skin has a low water content, making it an electrical resistor. Bone, tendons, fascia, and adipose tissue are also poor conductors of electrical currents because of their low water content (20% to 30%). Cell membranes have the greatest resistance to current flow. Muscle, nerve, and blood have a high water content (70% to 75%) and are good conductors of electrical currents. The internal organs, especially the heart, have a low ...

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