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Updated: May 5, 2026
In Vivo Measurement of Hindlimb Dorsiflexor Isometric Torque from Pig
Published on: September 3, 2021
Comparison of torque and discomfort produced by sinusoidal and rectangular alternating current electrical stimulation
1From the Center for Sensorimotor Research, Department of Neurology, Ludwig-Maximilians University, Munich, Germany (JS); and Discipline of Exercise and Sports Science, Faculty of Health Sciences, University of Sydney, Sydney, Australia (CF).
Objective:
The aim of this study was to investigate the effect of neuromuscular electrical stimulation burst duty cycle (BDC) and current type (sinusoidal alternating current [sAC] vs. rectangular alternating current [rAC]) on the electrically induced isometric torque (EIT) and discomfort. Pulsed current (PC) stimulation, which corresponds to one pulse rAC, was included in testing.
Design:
A repeated-measures design was used. The left quadriceps of 22 healthy subjects (mean ± SD age, 33 ± 8 yrs) were stimulated alternately with sAC and rAC current bursts (4-kHz carrier frequency; 71 bursts per second burst frequency) to produce isometric contractions. A range of BDCs were tested for sAC (7%-50%) and rAC (2%-18%) stimulation at fixed intensities while EIT and discomfort were recorded. BDC presentation order was randomized.
Results:
Overall, both current types elicited peak EIT at ∼14% BDC (range, 7%-21%). Significantly more EIT was produced by rAC than by sAC stimulation (P < 0.005). Discomfort increased with BDC and was similar for both current types.
Conclusions:
The study confirmed previous findings that conventional sAC stimulation (50% BDC) and pulsed current stimulation (rAC with 2% BDC) used in sports and rehabilitation produce similar EIT levels. However, rAC stimulation at low BDC (7%-18%) was more effective (+35% torque produced with similar discomfort) than pulsed current or conventional sAC.
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