Electrical Agents: Electrical Stimulation Techniques

1. Electrical Agents:Electrical Stimulation Techniques Body Circuit As the % of water in tissue increases, it�s ability to transmit electricity increases Tissues are either excitable (directly influenced by stimulation) or nonexcitable

3. Electrical Agents:Characteristics of Electrical Generators The current enters the body through a series circuit since the skin is relatively consistent Once in the body it may take many different paths Current prefers the path of least resistance

4. Electrical Agents:Electrodes Placement of electrodes is important for athlete comfort and efficiency Electrodes can be of different materials In most cases a medium is needed to reduce resistance between the skin and the electrode Wet sponges Conducting gels

5. Electrical Agents:Electrodes Size of electrode inversely affects the density of the current Electrode size ?= current density ? This affects comfort and effect of the current Larger electrodes produce greater contractions, but, not as specific

6. Electrical Agents:Electrodes Motor points, trigger points, acupuncture points Closer placement of electrodes vs. electrodes placed farther apart Closer = superficial Farther = deeper Direction of fibers is also important

7. Electrical Agents:Electrodes Bipolar Technique 2 leads, with equal size electrodes Monopolar Technique 1 or 2 active electrodes and a dispersive electrode Dispersive pad must be much larger than active electrodes

8. Electrical Agents:Electrodes Quadripolar Technique 2 sets of electrodes each from there own channels Current may intersect with each other

9. Electrical Agents:Movement of Electrical Current Most forms of electrical stimulation are applied transcutaneously When passed through the skin it has the potential to upset the resting potential of the axons Under the cathode = depolarization occurs Under the anode = hyperpolarization occurs

10. Electrical Agents:Selected Stimulation of Nerves Nerve�s response is based on 3 factors: Relative diameter of the nerve larger stimulated first Depth of nerve in relation to electrode sensory are closer to surface than pain/motor Duration of the pulse shorter durations require more current to stimulate a nerve type

11. Electrical Agents:Selected Stimulation of Nerves Sensory nerves are stimulated first, then motor, then pain. Pain fibers are located in between sensory and motor fibers, but, are smaller in diameter

12. Electrical Agents:Selected Stimulation of Nerves Subsensory-level From zero intensity to point athlete first feels the current Sensory-level To point of slight muscle contraction Motor-level Visable contraction without pain Noxious-level Intensity that stimulates pain fibers

13. Electrical Agents:Accommodation and Habituation Accommodation Over time it will take more intensity to cause depolarization of the nerve Habituation CNS filters out a continuous, non-meaningful stimulus This can be seen when an athlete gets use to the current

14. Electrical Agents:Movement of Electrical Current Medical Galvanism Application of low voltage DC, with a known polarity under each electrode Certain cellular and biochemical responses occur due to each polarity Galvanic stimulation is the only form of current that can elicits a muscle contraction from denervated muscle, but the phase duration is so long it also activates the C fibers

15. Electrical Agents:Movement of Electrical Current Medical Galvanism (Cont.) Physiological effects are generally opposite under the cathode or anode Symmetrical or balanced currents can not have any galvanic effects Unbalanced asymmetrical current can result in residual chemical changes is current is high enough

16. Electrical Agents:Electrical Stimulation Goals and Techniques Muscular Contractions Virtually any electric modality can achieve a contraction at a high enough intensity Contractions used to: Retard effects of atrophy Reeducate muscle Reduce edema Electrodes should be placed over motor points

17. Electrical Agents:Muscle Contractions Muscular Contractions (cont.) Large nerve closer to electrode are recruited first If nerve is denervated, then DC or monophasic with a long pulse duration can be used to depolarize the motor unit

18. Electrical Agents:Muscle Contractions Pulse Amplitude As intensity increases so does the strength of the contraction Depth of penetration increases as the peak current increases, thus recruiting more nerve fibers Pain inhibits maximal contraction of fibers

19. Electrical Agents:Muscle Contractions Pulse Frequency Pulse rate of less than 15 pps = twitch contraction Pulse rate between 15 and 40 pps = summation of stimuli This will increase to the point of tetany Further increase in frequency will promote fatigue of the muscle

20. Electrical Agents:Muscle Contractions Pulse Frequency (cont.) Strong tetanic contraction is needed to delay atrophy Low pps decreases fatigue, but, produces less force High pps are more comfortable

21. Electrical Agents:Muscle Contractions Phase Duration To recruit motor units a moderate phase duration should be used 300 to 500 microseconds Strength Augmentation Voluntary contractions are better than electrically induced contractions

22. Electrical Agents:Pain Control Reduce pain by assisting in the healing process or affecting pain transmission High pulse frequency, short duration, sensory level currents are thought to activate the gate control theory Low pulse frequency, long duration, high intensity and noxious stimuli are thought to stimulate release of opiates

23. Electrical Agents:Pain Control During initial phases of pain control, electricity stimulates the dorsal horn of the spinal cord The placebo effect of electrotherapy can not be overlooked

24. Electrical Agents:Circulation Electrically induced contractions increase local blood flow the same as voluntary contractions Sensory level stimulation has not been found to effect blood flow

25. Electrical Agents:Wound Healing Use of lower intensity DC may reduce the time needed for superficial wound healing by 1.5 to 2.5 times Depending on the polarity, certain inflammatory mediators can be attracted or repelled from the area

26. Electrical Agents:Wound Healing What occurs in the body: Increased circulation Increased blood clot formation Antibacterial effects Influences on migration of cells Presence of an �injury potential� (theorized to electrically control tissue repair)

27. Electrical Agents:Control and Reduction of Edema Sensory-level stimulation Attempts to stop formation of edema by preventing the fluids, plasma proteins, and other solids from escaping into surrounding tissues Motor-level stimulation attempts to assist the venous and lymphatic system in returning the edema substances back to the torso

28. Electrical Agents:Sensory-Level Stimulation for Edema Control Used in acute trauma to attempt to decrease edema formation Intensity is kept below motor threshold Why does it work? Reduction in capillary pressure and capillary permeability Produces a vascular spasm and prevents fluid from leaking out of the vessels

29. Electrical Agents:Motor-Level Stimulation for Edema Control Works by squeezing the vessels and �milking� the fluids out of the area Referred to as �muscle milking� or �muscle pump� Use 1 pps or tonic contraction with a 50% duty cycle Not as good as voluntary contractions If used limb should be elevated

30. Electrical Agents:Fracture Healing Electricity has traditionally been used to heal nonunion fractures Current research is also looking into acute fractures Theory: Bone cannot differentiate between the body�s innate charges need for normal bone growth and those from outside sources

31. Electrical Agents:Fracture Healing Devices are known as bone growth generators Generally use AC for transcutaneous use and DC for implanted electrodes Usefulness is debatable Decrease in bone growth Time out due to surgical implant & removal M.D. is the person who prescribes the unit

32. Electrical Agents General Contraindications: Cardiac disability (Stimulation of thorax or neck may effect respiration or heart) Pacemakers Pregnancy Menstration

33. Electrical Agents General Contraindications: (cont.) Cancerous lesions Sites of infections Exposed metal implants Severe obesity Epilepsy Electronic Monitoring Equipment

34. Electrical Agents Therapeutic Uses for Electricity: Controlling acute and chronic pain Reducing edema Reducing muscle spasm Reducing joint contractures Inhibiting muscle spasm Minimizing disuse atrophy Facilitating tissue healing

35. Electrical Agents Therapeutic Uses: (cont.) Facilitating muscle re-education Facilitating fracture healing Strengthening muscle