1. Neuromuscular Electrical Stimulation (NMES)
Mohammed TA, Omar, Ph.D. PT
Rehabilitation Health Sciences

2. Neuromuscular Electrical Stimulation (NMES)
Neuromuscular electrical nerve stimulation (NMES) is electrical Stimulation of The Excitable Tissue (Nerve & Muscle) Using Surface Electrodes to Induce Muscle Contraction Aiming to.
Muscle re-education
Prevention/Retardation of disuse atrophy
Muscle strength/endurance
Muscle pump contractions
Increasing range of motion
Reducing edema

3. What is the Motor Point? To trace motor point
A point on the skin where an electrical stimulus will cause the maximum contraction of an underlying muscle.
Area of greatest excitability on the surface of the skin overlying superficial muscles that can produce maximum contraction with minimum amount of current intensity.
Motor point is the region in muscle where a great density of terminal motor end plates is found near the surface.
The point where the motor nerve enters the muscle.
Motor point lies at muscles belly between the proximal one third and distal 2/3 of muscle belly or fleshy part of the muscle fibers.
To trace motor point
Interrupted direct current at 1ms (1000µs) for innervated muscle
Interrupted direct current at 100ms for denervated muscle

4. Position of the MP of quadriceps and gastrocnemii
What is the Motor Point?
To trace motor point
Interrupted direct current at 1ms (1000µs) for innervated muscle
Interrupted direct current at 100ms for denervated muscle
Position of the MP of quadriceps and gastrocnemii

5. Chart for Motor Point

6. Clinical practice ES parameters F(1-2Hz) Intensity (start 1mA)
Pulse duration µseconds
Pen electrodes (active)
Dispersive electrode
Alcohol swap (cotton) and markers
A, B, C, D,
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7. What is the Motor Unit? Motor unit
It is a single motor neuron (alpha motor neuron from anterior horn cell and all the muscle fibers it stimulate.
Each motor unit supplies from muscles fibers.
Dependent on movement precisions
e.g. Gastrocnemius 2,000 muscle fibers per motor neuron
Motor neuron determines fiber type .

8. What is the Motor Unit?

9. Sensory Nerve Impulses
When sensory nerve is stimulated the downward traveling impulse has no effect, while the upward traveling impulse is appreciated at the conscious level of the brain.
Orthodromic propagation: is propagation of nerve impulse toward the sensory cortex.
Antiodromic propagation: is propagation of nerve impulse toward the periphery (sensory receptors on the skin).
Long pulse duration ≥ 10ms (comfortable stabbing sensation).
Short pulse duration of ≤ 1ms (mild/moderate prickling sensation).

10. Motor Nerve Impulses
When motor nerve is stimulated the upward traveling impulse is unable to pass the first synapse, while downward traveling impulse passes to the muscles supplied with that nerve causing the contraction.
Antidromic Propagation: it is a propagation of nerve impulse proximally toward the CNS.
Orthdromic Propagation: it is a propagation of nerve impulse periphery toward neuromuscular junction.
When a stimulus is applied to nerve trunk, or innervated muscle impulse pass to all the muscles that nerve supplies below the point at which it is stimulated, causing them to contract.

11. Strength Duration Curve (SD)
The SD curve is a graph representation of a quantitieves non liner relationship between intensity and duration of current to determine whether a muscle is innervated, or denervated.
It depends on;
Numbers of motor units recruitment
Intensity of current.
Frequency
Placement of electrodes.

12. Strength Duration Curve (SD)
Rheobase is a minimal intensity of the current required to produce a minimal visually perceptible muscle contraction (300ms).
Normal values of Rheobase are (2-18mA, 5-35volts)
Chronaxie is a minimal pulse duration required to produce a minimal perceptible response in a muscle, at twice the intensity of rheobase.
Chronaxie of innervated muscles is less than 1ms (range ms).
Chronaxie of fully denervated muscle may be 30 to 50 ms

13. Muscles that have loss nerve supply.
Denervated Muscles;
Muscles that have loss nerve supply.
Deneravtion ranges from complete denervation (CD) to partial deneravation (PD).
Complete denervation (CD), all motor unit loses all innervation
Partial denervation (PD) some of motor unit in the muscles lose its innervation
Results in Atrophy or Wasting
Muscle atrophy is a reduction in size of muscles (disease/ disuse).
Muscle wasting is the unintentional loss of 5–10% of muscle mass.
Normal Innervation: All nerve fibers supplying the muscle are intact

14. Stimulation of Denervated Muscles
Physiological & chemical characteristics of denervated muscles
Long Duration Interrupted direct current (LIDC)
Current parameters and specifications
Effect of ES on denervated muscles

15. Physiological &chemical Characteristics of Denervated Muscles
Decrease size, and diameter of muscles fibers.
Decrease amount of tension generated
Increase time required for contraction
Degenerative changes progress until muscle is reinnervated by axons regenerating across site of lesion (2-6months)
If reinnervation does not occur within 2 years fibrous connective tissue replaces contractile elements and recovery of muscle function is not possible

16. EFFECTS of DENERVATION in SKELETAL MUSCLES
Paralysis (immediately):
Fasiculation (immediately): spontaneous firing of the injured axon, causing twitching of motor units.
Fibrillation (days) : spontaneous twitching of individual muscle fibers due changes in muscle excitability (e.g., Na channels)
Muscle atrophy (>1 week):
Receptiveness to innervation: allows reinnervation of the muscle by motor axons

17. Long Duration Interrupted Direct Current
Unidirectional, interrupted direct current with following characteristic;
Pulse
duration
Inter-Pulse
Interval
Frequency
Long pulse duration (100ms-600ms)
ms PD
≥ 300ms CD
Depends on pulse duration e.g. If Pulse duration = 100ms
Frequency of 1.5 Hz.
3-5times of pulse duration.
Waveforms shape: Saw-tooth, Triangular, & Trapezoid

18. Stimulating Denervated Muscle
First 2 weeks.
Use asymmetric, biphasic waveform and pulse duration < 1 ms
After 2-3 weeks,
Interrupted DC square wave with long pulse duration > 10 ms,
AC sine wave with frequency < 10 Hz
Inter-Pause interval 3 to 5 times longer (about 3-6 seconds) than stimulus duration to minimize fatigue.
Use monopolar or bipolar electrode setup with small diameter active electrode placed over most electrically active point.
Stimulation using 3 sets of repetitions, 3/ per week

19. triangular, trapezoidal
Effects of LIDC
Neuropraxia
100ms, rectangular
Axonotmesis
ms,
triangular, trapezoidal
Neurotmesis ms
triangular, saw-tooth

20. Effect of ES on Denervated Muscles
Retardiation of denervated atrophy
Utilization of substrates
Prevent venous & lymphatic stasis
Working hypertophy
Maintenance of muscle extensibility

21. NMES- Faradic Current

22. Faradic Current Stimulation
Faradism is unevenly alternating current with each cycle consisting of two unequal phases, with frequency 1-150Hz.
B-Negative: Low intensity long duration
A-Positive: High intensity short duration A B

23. Faradic Current Stimulation
Faradic current is a short-duration interrupted Surged direct current with a pulse duration of 0.1 to 1ms, and frequency of Hz
Pulse duration (0.02-1ms)
Therapeutic selection 0.02, 0.05, 0.1 & 1ms.
PD=0.1ms , frequency of 70Hz, & Skin resistance = 50Ώ,
PD=1ms with frequency of 50Hz, and skin resistance = 1000Ώ
Polarity :Active electrodes usually the cathode (-)
Faradic currents are always surged and interrupted for treatment purposes to produce a near-normal tetanic like muscles contraction and relaxation.
Faradic current is surged so that the intensity of successive impulse increases gradually, each phase reaching a peak value greater than the preceding one, and than fail either gradually or suddenly (why).
The current is surged at variable controlled speeds ranging from 4-30surged/minute with variable rest period.
The surge can be modified to give surges of various duration, frequency and waveforms.
Faradic current will not stimulate denerveated muscles, as the current required to stimulate dennervated muscles at 1ms, is usually too great to be tolerable by the patients..

24. Faradic Current Stimulation
Faradic current is a short-duration interrupted Surged direct current with a pulse duration of 0.1 to 1ms, and frequency of Hz
Frequency:
Therapeutic frequency (0.5, 1.5, 10, 50, 75, 100 Hz)In order to achieve a constant contraction, the stimulus must be applied at rate of 30-60stimuli per seconds.
Waveforms
Rectangular shaped pulse more comfortable than triangular pulse for normal muscle contraction.
If disuse atrophy triangular waveform can be used.
Pulse duration (0.02-1ms)
Therapeutic selection 0.02, 0.05, 0.1 & 1ms.
PD=0.1ms , frequency of 70Hz, & Skin resistance = 50Ώ,
PD=1ms with frequency of 50Hz, and skin resistance = 1000Ώ
Polarity
Active electrodes usually the cathode (-)
Faradic currents are always surged and interrupted for treatment purposes to produce a near-normal tetanic like muscles contraction and relaxation.
Faradic current is surged so that the intensity of successive impulse increases gradually, each phase reaching a peak value greater than the preceding one, and than fail either gradually or suddenly (why).
The current is surged at variable controlled speeds ranging from 4-30surged/minute with variable rest period.
The surge can be modified to give surges of various duration, frequency and waveforms.
Faradic current will not stimulate denerveated muscles, as the current required to stimulate dennervated muscles at 1ms, is usually too great to be tolerable by the patients..

25. Physiological Effects of Faradic Stimulation
Sensory nerves
Mild prickling due to stimulation of sensory nerve .
Mild erythema due to local reflex vasodilatation of superficial blood vessels, which causes slight reddening of the superficial tissues.
Motor nerves
Faradic current stimulates the motor nerves /muscle, causes contraction of the muscles.
Because the stimuli repeated 50 times (50Hz) or more, the contraction is titanic.
To avoid muscle fatigue secondary to this contraction the current becomes surged
Effects on motor nerve

26. Effects of Muscle Contraction
Increased muscle metabolism.
Increase oxygen demand by the muscles.
Increase output of waste product & metabolites (carbon dioxide, lactic acid).
Dilatation of capillaries and arterioles
Increased blood flow
Increase local temperature.
Increase venous and lymphatic drainage
Changes in muscle structure (fast twitch to slow twitch )
Increase joint range of motion.

27. Therapeutic Uses and Indication of Faradic Current Stimulation

28. Facilitation of Muscle Contraction & Re-education
Pain & muscle spasm,
Quadriceps e.g. vastus medialis after knee injury & diseases
Prolonged disuse, wasting and imbalance
Intrinsic muscle of foot in case of longstanding flat foot.
Abductor hallucis in hallux valgus.
Scoliosis.
Prolonged period of immobilization
Muscle and nerve repair and transplantation.
Nerve injury (----What is the degrees of nerve injury?)
Pelvic floor Muscle (stress incontinence)

29. Improve Venous and Lymphatic drainage
Electrical stimulation of the muscle causes increase venous and lymphatic return, alter cell membrane permeability, these causes reduction of edema.
The treatment is most effective if the current is applied by the method, termed faradism under pressure
Faradism under pressure is stimulation of the muscle that generally act as the pump muscles and is combined with compression and elevation of the limb to increase venous and lymphatic drainage and hence relive edema.

30. Retardation of muscle atrophy Increasing Range of Motion
Maintenance of muscle tissue after injury that prevent normal muscle contraction can be achieved through using an electrical stimulated muscle contraction, which produce the physical and chemical events associated with normal voluntary muscle contraction and helps to maintain normal muscle function.
Increasing Range of Motion
Muscle contraction pulls the joint through limited range. The continued contraction of this muscle group over an extended time make the contracted joint and muscle tissues modify and lengthen

31. The person with foot drop is unable to dorsiflex their foot.
APPLICATIONS
The right quad has atrophied or wasted. Stimulation of the quad can prevent atrophy and increase strength.
The person with foot drop is unable to dorsiflex their foot.
The approximate electrode placements for foot drop. The negative is placed over the peroneal nerve.
Placement for quad weakness/atrophy.

32. Muscle re-education Rotator cuff repair Post op ACL
Problem: Rotator cuff atrophy, poor scapular stability
Goal: Decrease/ reverse atrophy, scapular stabilizer re-ed.
Waveform: Symmetric/ asymmetric
Duty cycle: 25%, hand switch
Placements:
Post op ACL
Problem: Quadriceps atrophy
Goal: Decrease atrophy, increase strength.
Waveform: Symmetric
Duty cycle: 25% (4:12)
Placements:
Isometric Abduction
Scapular depression

33. Contraindication for Faradic Current Stimulation
Skin lesion & dermatological conditions such as eczema.
Infection such as osetomylities.
Vascular diseases such as thrombosis, & thrombophlebities.
Marked loss of skin sensation (chemical burn).
Unreliable patients.
Superficial metal (concentration of electricity).
Metal and cardiac pacemaker
Over recent or non-union fractures
Over potential malignancies

34. Treatment times & frequency
To be effective 2 & 3 treatments per week for the first 8-12 weeks
Treatments last minutes but no longer than 30 minutes
It is better to have 3 short treatments per week than 1 long treatment