BPA Unit 6: E-Stim for Muscle Contraction

Question 1

What is Neuromuscular Electrical Stimulation (NMES)? What is its purpose?

Answer 1

This induces contraction of skeletal muscles

Purpose
- Muscle strengthening
- Disuse atrophy
- Spasm or spasticity reduction
- Edema reduction
- Improve ROM

Question 2

What is the difference between Voluntary and NMES Contraction?

Answer 2

Voluntary:
- Progressive recruitment of muscle fibers
- Slow, typically small, motor units followed by fast, typcially large, motor units
- Asynchronous motor unit recruitment patterns

NMES:
- Nonselective manner recruitment, both small and large motor units are recruited
- This usually occurs in a spatially fixed and temporally synchronous pattern

Question 3

What are the 2 types of NMES?

Answer 3

• Russian Current
• Pulsed Current

Question 4

With Russian, what are the parameters for Burst Modulated Alternate Current (PMAC)?

Answer 4

• 25 cycles in 10msec = 2,500Hz carrier frequency
• 2 burst in 40msec = 50 burst per sec

Question 5

With the force frequency relationship, what is Tetany?

Answer 5

The point where further increases in frequency do no produce increases in force production

Question 6

What are the NMES parameters for Muscles Strengthening?

Waveform, Pulse duration, frequency, ramp up/down, treatment time, Carrier frequ., Burst duration, Relative duty cycle

Answer 6

• Waveform: Symmetrical biasic pulse current (e.g., russian)
• Pulse Duration: 200 μsec
• Frequency: 50 Hz
• Ramp up: 1 sec
• Ramp down: 1 sec
• Duty Cycle 1:3 to 1:5 with on-time to 10 sec and off time up to 50 sec
• Treatment Time: At least 10 contractions (3-5 times /wk, 4-8 wks)
• Carrier Frequncy: 2500Hz
• Burst Duration: Burst Fequency 50Hz
• Relative Duty Cycle: 1:3 - 1:5

Question 7

With NMES, what are the Stimulation Parameters Considerations?

Answer 7

• Muscle Strength: The highest pulse duration and amplitude tolerated by the patient should be used
• The frequency should by adjusted to achieve a smooth, foreful contraction above 30 pulses per second (pps or Hz)
• High stimulation frequencies (pps or Hz) such as 100 Hz or above, may generate greater muscle fatigue

Question 8

With NMES stimulation parameters considerations, how do we avoid fatigue?

Answer 8

• Reducing the frequency
• Increasing the rest time between contraction

Question 9

With NMES stimulation parameters considerations, what should be considered with Ramp Time?

Answer 9

• Shorter times are recommended
• 1 or 2 seconds are ideal

Question 10

With NMES stimulation parameters considerations, what should be considered with Intensity?

Answer 10

• Contractions near maximal tolerance
• 50 -70% of the MVC of the opposite limb are common in studies reporting increased strength following NMES

Question 11

How does Electrical Stimulation activate muscle fibers? What are the Necessary parameters for this?

Answer 11

By depolarizing the sarcolemma and not via peripheral nerves. NMES is for innervated muscle

Necessary Parameters
- Long pulse duration
- Greater amplitude of stimulation
- Different waveforms (direct current, greater risk of skin burns)

Question 12

What are the Contraindicatios for NMES?

Answer 12

They should not be placed over…
- The tunk or heart region with pacemakers or ICDs
- The Pelvic, abdmoninal, lumbar, or hip region with pregnant women
- Carotid bodies
- Phrenic nerve or urinary bladder stimulators
- Areas of known PVD
- Areas of active osteomyelitis
- Areas of hemorrage