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document
The effect of random modulation of functional electrical stimulation parameters on muscle fatigue . Muscle contractions induced by functional electrical stimulation ( FES ) tend to result in rapid muscle fatigue , which greatly limits activities such as FES-assisted standing and walking . It was hypothesized that muscle fatigue caused by FES could be reduced by randomly modulating parameters of the electrical stimulus . Seven paraplegic subjects participated in this study . While subjects were seated , FES was applied to quadriceps and tibialis anterior muscles bilaterally using surface electrodes . The isometric force was measured , and the time for the force to drop by 3 dB ( fatigue time ) and the normalized force-time integral ( FTI ) were determined . Four different modes of FES were applied in random order : constant stimulation , randomized frequency ( mean 40 Hz ) , randomized current amplitude , and randomized pulsewidth ( mean 250 micros ) . In randomized trials , stimulation parameters were stochastically modulated every 100 ms in a range of +/-15 % using a uniform probability distribution . There was no significant difference between the fatigue time measurements for the four modes of stimulation . There was also no significant difference in the FTI measurements . Therefore , our particular method of stochastic modulation of the stimulation parameters , which involved moderate ( 15 % ) variations updated every 100 ms and centered around 40 Hz , appeared to have no effect on muscle fatigue . There was a strong correlation between maximum force measurements and stimulation order , which was not apparent in the fatigue time or FTI measurements . It was concluded that a 10-min rest period between stimulation trials was insufficient to allow full recovery of muscle strength .
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Intervention_Physical
random modulation of functional electrical stimulation parameters
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Intervention_Physical
functional electrical stimulation
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Outcome_Physical
rapid muscle fatigue
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Outcome_Physical
muscle fatigue
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Outcome_Physical
isometric force
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Outcome_Physical
force-time integral ( FTI )
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Outcome_Physical
fatigue time measurements
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Outcome_Physical
FTI measurements
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Outcome_Physical
muscle fatigue
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Outcome_Physical
fatigue time
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Outcome_Physical
FTI measurements
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Outcome_Physical
recovery of muscle strength
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Participant_Condition
muscle fatigue
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Participant_Sample-size
Seven