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Updated: Feb 24, 2026
Determining The Electromyographic Fatigue Threshold Following a Single Visit Exercise Test
Published on: July 27, 2015
M-wave normalization of EMG signal to investigate heat stress and fatigue
Olivier Girard1, David J Bishop2, Sébastien Racinais3
1Athlete Health and Performance Research Centre, Aspetar Orthopaedic and Sports Medicine Hospital, Qatar; Institute of Sport Sciences, Lausanne University, Switzerland.
Objectives:
We examined the extent to which peripheral changes affect EMG signal adjustments during repeated sprinting in temperate and hot conditions.
Design:
Randomised, crossover study.
Methods:
Ten males performed 10×6-s 'all-out' cycling sprints (recovery=30s) in either a temperate (24°C/30%rH) or a hot (35°C/40%rH) environment with concomitant surface EMG recordings of the vastus lateralis (VL) and rectus femoris (RF). In addition, peak-to-peak M-wave amplitudes were obtained for each muscle after each sprint (i.e., 15s into recovery).
Results:
For both the VL and RF muscles RMS decreased across sprint repetitions (P<0.01), while significantly lower values for the VL (P=0.012), but not the RF (P=0.096), occurred in hot vs. temperate conditions. M-wave-normalised RMS for VL muscle decreased across sprint repetitions (P=0.030), with no condition or interaction effects (both P>0.621). M-wave-normalised RMS for the RF muscle was lower in the heat (P<0.034), with no significant sprint or interaction effects (both P>0.240).
Conclusions:
Controlling for changes in maximal M-wave amplitude of the quadriceps muscles after each bout of a repeated cycling exercise in hot and temperate conditions allows researchers to account for fatigue- and/or heat-induced neural and peripheral adjustments.
