Effects of stimulation frequency, amplitude, and impulse width on muscle fatigue

INTRODUCTION: We investigated the effect of stimulation intensity (in percent of maximal tolerated stimulation current, mTSC), frequency, and impulse width on muscle fatigue.

METHODS: Using a randomized crossover design, 6 parameter combinations (80% mTSC, 80 Hz, 400µs; 60% mTSC, 80 Hz, 400 µs; 80% mTSC, 20 Hz, 400µs; 60% mTSC, 20 Hz, 400 µs; 80% mTSC, 80 Hz, 150 µs; 60% mTSC, 80 Hz, 150 µs) were tested in both legs of 13 athletic men (age 26 ± 2.3). The slope of the linear regression line over all tetani (FIS) and the number of tetani whose force was above 50% of the initial tetanus (FIN) were used to quantify fatigue.

RESULTS: FIS and FIN were significantly lower in high-frequency protocols. No effects on FIS and FIN were found for intensity and impulse width.

DISCUSSION: Stimulation frequency, but not impulse width or intensity, affected fatigue kinetics. This article is protected by copyright. All rights reserved.