The effect of duty cycle and frequency on muscle torque production using kilohertz frequency range alternating current

We investigated the frequency and duty cycle dependence of maximal electrically induced torque (MEIT) of the wrist extensors. Fifty hertz burst modulated sinusoidal alternating current (AC) in the frequency range 0.5–20 kHz was used, with duty cycles ranging from a minimum (one cycle) to maximum (co...

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Bibliographic Details
Published in:Medical engineering & physics 2004-09, Vol.26 (7), p.569-579
Main Authors: Ward, Alex R, Robertson, Valma J, Ioannou, Harry
Format: Article
Language:English
Subjects:
Alternating current
Duty cycle
Electric Stimulation Therapy
Electrical stimulation
Electrophysiology
Frequency
Humans
Muscles - physiology
Muscles - radiation effects
Neurons - physiology
Pulse
Sensory Thresholds
Torque
Transcutaneous Electric Nerve Stimulation - methods
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Summary:We investigated the frequency and duty cycle dependence of maximal electrically induced torque (MEIT) of the wrist extensors. Fifty hertz burst modulated sinusoidal alternating current (AC) in the frequency range 0.5–20 kHz was used, with duty cycles ranging from a minimum (one cycle) to maximum (continuous AC). MEITs were similar at low frequencies but decreased markedly above 2.5 kHz. MEITs also decreased markedly above a 20% duty cycle. Subjective reports of discomfort were fewest at 4 kHz and at duty cycles in the range 20–25%. Our conclusion is that for maximum torque production, a frequency of 1 kHz and a duty cycle of 20% are indicated. When comfort is a major consideration, a frequency of 2.5 kHz provides an acceptable trade-off between MEIT and comfort. The findings also suggest that low duty cycle, burst modulated AC stimulation may be more effective than stimulation using conventional low-frequency pulsed current.
ISSN:1350-4533
1873-4030
DOI:10.1016/j.medengphy.2004.04.007