Comparing the force ripple during asynchronous and conventional stimulation.
BACKGROUND
Asynchronous stimulation has been shown to reduce fatigue during electrical stimulation; however, it may also exhibit a force ripple. We quantified the ripple during asynchronous and conventional single-channel transcutaneous stimulation across a range of stimulation frequencies.


METHODS
The ripple was measured during 5 asynchronous stimulation protocols, 2 conventional stimulation protocols, and 3 volitional contractions in 12 healthy individuals.


RESULTS
Conventional 40 Hz and asynchronous 16 Hz stimulation were found to induce contractions that were as smooth as volitional contractions. Asynchronous 8, 10, and 12 Hz stimulation induced contractions with significant ripple.


CONCLUSIONS
Lower stimulation frequencies can reduce fatigue; however, they may also lead to increased ripple. Future efforts should study the relationship between force ripple and the smoothness of the evoked movements in addition to the relationship between stimulation frequency and NMES-induced fatigue to elucidate an optimal stimulation frequency for asynchronous stimulation.
Department of Mechanical and Aerospace Engineering, University of Florida, Gainesville, Florida, 32611-6250, USA.
Ryan J
RJ
Downey
Mark
M
Tate
Hiroyuki
H
Kawai
Warren E
WE
Dixon
D000328:Adult; D001703:Biophysics; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D019415:Torque; D004561:Transcutaneous Electric Nerve Stimulation; D055815:Young Adult
asynchronous stimulation; force ripple; functional electrical stimulation; muscle fatigue; neuromuscular electrical stimulation; torque ripple