motor point

A motor point is a specific skin area where the targeted muscle is best stimulated with the smallest amount of current amplitude and the shortest pulse duration

1. MOTOR POINTS

2. OBJECTIVES: Motor Point Definition Location Advantages Reactions Physiological effects Currents Electrodes Indications Contraindications Precautions Application principles Motor points of muscles

3. Motor point CLINICALLY; A motor point is a specific skin area where the targeted muscle is best stimulated with the smallest amount of current amplitude and the shortest pulse duration ANATOMICALLY; This same motor point is defined as the surface entry point of a bundle of motor nerve fibers into a fasicle of muscle fibers

4. LOCATION Motor points are frequently at the junction of the upper and middle one-thirds of the fleshy belly of the muscles Motor points vary from person to person. Motor point of deeper muscles are difficult to locate. Deeply placed muscles may be stimulated where they emerge from beneath the more superficial ones

5. WHY TRACING OF MOTOR POINT IS ESSENTIAL???? Tracing of a motor point is essential for; 1-Plotting of a SD curve of a muscle 2-Locating the general area for electrode placement for surged faradic stimulation of innervated muscles

6. ADVANTAGES OF MOTOR POINT STIMULATION The current intensity required to produce muscle contraction is minimum, compared to any other area on the muscle belly, thus causing mild sensory irritation.

7. ADVANTAGES OF MOTOR POINTS Specific muscle performs its own individual action and that the optimum contraction of each can be obtained. It may therefore be selected when training a new muscle action or when isolation of one muscle is indicated; e.g. the vastus medialis may be stimulated to overcome a quadriceps lag,or abductor hallucis for muscle weakness.

8. REACTIONS The application of an electrical stimulus on the skin (motor points), via an electrode, will cause the following reactions: Can cause the underlying muscle to contract and will elicit the greatest muscular contraction. Can cause pumping action on blood vessels, improving the venous return, thus inc. in blood flow to the area. Can produce muscle contraction in a partially denervated muscle.

9. PHYSIOLOGICAL EFFECTS

10. EXCITABILITY OF NERVE CELLS When a nerve is stimulated the stimulus causes a fall in the potential difference across the plasma membrane which is termed as ACTION POTENTIAL + + + + + + + ++ + - - - - - - - - - - - - - - - K + Na +

11. STAGES OF AP RESTING STAGE DEPOLARIZATION STAGE REPOLALARIZATION STAGE

12. Resting stage This is membrane potential of nerve fibers when they are not transmitting signals The RMP in excitable cells as in nerve cells is -70mV and muscle cells is approximately -90mV

13. DEPOLARIZATION STAGE This is the change in the resting membrane potential from -90mV to 0mV and then to a positive value 35mV

14. REPOLARIZATION STAGE This is a change in the membrane potential from positive to a negative value 35mV to -90mV

15. - 90 -80 -70 -60 -50 -40 -30 -20 -10 0 +10 +20 +30 +40 mv Threshold of muscle and nerve Action potential of nerve Action potential of muscle

16. CURRENTS USED

17. Most commonly used currents for stimulatory purposes of nerve and muscles are; Faradic type of current Russian current High Voltage current TENS (burst mode)

18. FARADIC TYPE CURRENT An interrupted direct currents with a pulse duration of 0.2 to 1 msec. The most comfortable pulse is 0.1 at 70 Hz

19. RUSSIAN CURRENT A 2500 Hz AC modulated every 10ms to provide 50 bursts per sec.

20. HIGH VOLTAGE CURRENT A twin-spike Waveform: monophasic pulsed current pulse duration: 5-65 s Freq : 1-120 pps (low pps ) Peak amp: 500 V (2000-2500 mA) 5-65 µs

21. TENS (burst mode) Frequency : 50 to 100 pps Phase/pulse duration: 50 to 200 microsecond Amplitude : comfortable /intermittent Electrode placement : over motor points Duration of treatment : 15 to 20 minutes Indications: acute as well as chronic pain.

22. Effect of Pulse Frequency on Muscle Contractions 1 pulse per second Twitch Contraction The amount of time between pulses – the interpulse interval – is long enough to allow the muscle fibers to return to their original position 20 pulses per second Summation The amount of time between pulses allows some elongation of the fibers, but not to their starting point. 40 pulses per second Tonic Contraction The current is flowing so rapidly that there is not sufficient time to allow the fibers to elongate

23. ELECTRODES USED

24. SIZE OF ELECTRODES Current density inversely proportional to the electrode contact area

25. METHODS OF ELECTRODE PLACEMENT UNIPOLAR (Bifurcated) BIPOLAR QUARDRIPOLAR

26. Metal electrode ( small lint/sponge pad with a flat plate-electrode.) Carbonised Rubber Electrode Specialised probe

27. Unipolar Motor Point Stimulation Electrodes of 2 different sizes Active Electrode – placed where the treatment effect occurs; may be bifurcated Dispersive Electrode – completes the circuit; fastened to a body part @ a distant location (large body mass) Site of stimulation: motor point for stronger response Smaller sized electrode has higher current density (stronger effect) Little or no stimulation should occur under dispersive electrode

28. Bipolar Motor Point Stimulation Electrodes equal or near-equal size electrodes Both electrodes are located in target treatment area Equal amount of current from each electrode Effective for stimulating muscle groups or very large muscles

29. Quadripolar Motor Point Stimulation Uses 2 sets of electrodes, 2 from each own channel. Electrodes from two or more circuits positioned so that currents geometrically intersect.

30. INDICATIONS Muscle strengthening and or muscle exercise Treatment of disuse atrophy Muscle re-education of movement Muscle contraction in partially denervated muscles Pumping actions.

31. CONTRAINDICATION Cardiac disability Demand-type pacemakers Pregnancy (over lumbar and abdominal area) Menstruation (over lumbar and abdominal area) Cancerous lesions (over area) Sites of infection (over area) Epilepsy In the presence of electronic monitoring equipment Exposed metal implants

32. PRECAUTIONS Sensory loss over treatment site Open wounds Extreme edema or severe obesity Areas of sensitivity Carotid sinus Esophagus Larynx Pharynx Around the eyes Temporal region Upper thorax

33. APPLICATION PRINCIPLES Conduct general safety checks with respect to the equipment. Check the patient for contraindications Explain the treatment fully to the patient Collect the necessary equipment ES, electrodes, wiring Soap & water for cleaning the skin Contact gel / sponge, tape / straps

34. Cont ……… Position the patient in the comfortable position The skin should be uncovered & examined for any contraindications to treatment Test the equipment as appropriate; demonstrate the technique to the patient. Wash the skin over the region of electrode contact. Soaking the skin for 3-4 min either in a bath or with a warm, damp pad may reduce skin resistance. Select appropriate treatment parameters.

35. Cont …… Always turn all intensity dials to zero before beginning the treatment Place the electrodes as appropriate for the treatment. Increase intensity until desired result is produced Never lift the active electrode from the skin or replace it without turning the intensity to zero. Terminate the treatment; check the skin condition Keep a full record of the treatment

36. MOTOR POINTS OF MUSCLES IN DIFFERENT REGION/PART OF THE BODY

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