Résumé
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 x 6-s 'all-out' cycling sprints (recovery = 30 s) 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., 15 s 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. (C) 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.