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Updated: Apr 7, 2026
Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test
Published on: July 27, 2015
Quadriceps mechano- and electromyographic time-frequency responses during muscular contractions to volitional
Ronald Croce1, Amber Craft1, John Miller1
1Motor Control and Biomechanics Laboratory, Department of Kinesiology, University of New Hampshire, Durham, New Hampshire, 03824, USA.
Introduction:
Surface electromyography (SEMG) and mechanomyography (SMMG) responses of the quadriceps during muscular contractions to exhaustion were computed and analyzed by analysis of variance and polynomial regression analyses.
Methods:
Participants performed maximum flexion-extension movements at 180°/s until volitional exhaustion, rested for 2 minutes, and then completed a second bout of movements until exhaustion. Torque and SEMG/SMMG median frequencies and amplitudes were examined at 9 points across repetitions completed.
Results:
(1) Torque decreased precipitously; (2) SEMG amplitude displayed an initial increase, then a steady decrease, and SMMG amplitude showed a continuous decrease; and (3) SEMG and SMMG median frequencies displayed a continual decrease over repetitions completed. Fractional polynomial and quadratic models explained the fatigue process with the highest precision.
Conclusions:
Changes in electrical and mechanical properties of the quadriceps during fatigue reflect alterations in neuromuscular activation strategies and/or muscle wisdom. SEMG frequency modeled muscle fatigue more effectively than amplitude, whereas SMMG frequency and amplitude were equally effective.
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