Influence of kilohertz frequency, burst duty cycle and burst duration on evoked torque, discomfort and muscle efficiency : a randomized crossover trial

Abstract

Kilohertz-frequency alternating currents (KFACs) have been indicated to mini-mize muscle atrophy and weakness. However, the optimal stimulation param-eters still need to be determined.Objective: This study aimed to investigate the effects of different KFACs onevoked torque, current efficiency, and perceived discomfort.Design: KFACs with frequencies of 1 kHz (Aussie current) and 2.5 kHz (Russiancurrent), along with two duty cycles (10% and 20%), were randomly applied to thetriceps surae muscle of healthy participants using a crossover design. The NMESintensity, NMES-evoked torque, NMES efficiency, and NMES discomfort weremeasured in maximal and submaximal conditions. Statistical analyses were con-ducted using a two-way mixed- model ANOVA with repeated measures. Forty-four participants were included.Results: Aussie currents produced higher evoked torque and efficiency in maxi-mal and submaximal efforts, with higher perceived discomfort in maximal ef-fort. Although the Australian current may cause greater discomfort at maximalefforts, it matches the Russian current in perceived discomfort at submaximallevels. The 20% duty cycle produced the highest efficiency in submaximal efforts.Conclusion: In both maximal and submaximal efforts, the Aussie current dem-onstrated superior NMES efficiency, yielding higher torque with lower amplitudethan the Russian current. Clinicians should take these findings into considera-tion when prescribing KFACs to optimize clinical outcomes.