Electrical stimulating currents

Electrical stimulating currents are among the therapeutic modalities most often used by the sports therapist. The effects of electrical current passing through biological tissues may be physiological, chemical, or thermal. All biological tissue has some response to this current flow. The type and extent of the response depends on (1) the type of tissue and physiological response characteristics and (2) the parameters of the electrical current applied, that is, its intensity, duration, waveform, modulation, and polarity. Biological tissue responds to electrical energy in a manner similar to how it normally functions and grows.

Clinically, the sports therapist uses electrical currents for several purposes: (1) producing muscle contraction through stimulation of nerve muscle, (2) stimulating sensory nerves to help treat pain, (3) creating an electrical field on the skin surface to drive ions into tissues (iontophoresis), and (4) creating an electrical field within the tissues to stimulate or alter the healing process (medical galvanism). In a sports-medicine environment, the major therapeutic uses of electricity center on muscle contraction, sensory stimulation, or both.

To produce any physiological response in the nerve and muscle fibers, an electrical current must be of sufficient intensity and last long enough to equal or exceed the nerve membrane's basic threshold for excitation. When this occurs, depolarization of the nerve fiber results in an action potential.

Different types (sizes) of nerves have different thresholds for depolarization. The strength/duration curves in Figure below represent graphically the thresholds for depolarization of sensory, motor, and pain nerve fibers. If current intensity or duration is increased to a level great enough to reach the minimal threshold for depolarization of sensory fibers, the electrical current can be felt. If current intensity or duration is increased further, a muscle contraction may be elicited by reaching the threshold for depolarization of the motor fibers. If the intensity/duration continues to increase, eventually a level is reached that causes depolarization of the smaller fibers and pain. By simply changing current intensity, current duration, or some combination of the two, very different physiological responses can be achieved.

Traditionally, various types of electric currents have been classified by attaching specific names, such as high volt, low volt, alternating, direct, interferential, Russian, and microamperage (MENS). Electrical stimulators that output any of these varieties of current (with the possible exception of some new MENS units in which the intensity is not great enough) can produce any of these physiological responses if the current parameters are adjusted appropriately. Thus a discussion of the physiological effects of electrical current on the stimulation of sensory nerves and motor nerves is appropriate.

3.1. Listen to the text “Electrical Simulating Currents”.

3.2. Read and translate the text.

3.3. Give its main idea in your native language.

3.4. Answer the questions.

1. Are electrical stimulating currents often used by the sports therapists? 2.

What kinds of effect could be from electrical currents passing through biological tissues? 3. What do the type and extent of biological tissue response depend on? 4. Similar to what does biological tissue respond to electrical energy? 5. For what purposes do the sports therapists use electrical currents clinically? 6. How intensive and long must an electrical current be in order to produce response in the nerve and muscle fibers? 7. When does depolarization of the nerve fiber result in an action potential? 8. Do different types (sizes) of nerves have different thresholds for depolarization? 9. At which type of depolarization threshold can the electrical current be felt? 10. What occurs if current intensity or duration is increased further? 11. At what level does that cause depolarization of the smaller fibers and pain? 13. How can very different physiological responses be achieved? 14. What are the traditional names of various types of electric currents? 15. The electrical stimulators that output any of these varieties of current can produce any of these physiological responses if the current parameters are adjusted appropriately, can’t they?

Strength-duration curves Curves represent the thresholds for depolarization of the various types of nerve fibers. Ab, Sensory nerves; Ad, motor fibers; C, pain fibers

3.5. Discuss the text “Electrical Stimulating Currents” using the Figure below.

3.6. Translate the following into English.

РУССКИЙ ТОК (RUSSIAN CURRENT)

Русский ток является относительно новым типом токов, используемых спортивными врачами. Это переменный ток (AC current) высокой частоты (at a high frequency), испускаемый сериями зарядов (импульсов) (produced in a series of “bursts”). Благодаря импульсивному характеру достигается большая интенсивность тока, а для спортсмена такая процедура более терпима (the athlete will have a high tolerance to the current). Увеличивается интенсивность стимуляции, стимулируется большое число мышечных волокон, и ярче выражены сокращения (a stronger contraction occurs). При использовании для укрепления мышц этот ток наиболее эффективен в сочетании с активным мышечным сокращением при преодолении сопротивления (с усилием) (when combined with active muscle contraction against resistance).

3.7. Retell the oral topic “Therapeutic Modalities in Rehabilitation”.