The effect of heat stress on motor preparation processing

Abstract

An excessively increased internal temperature is known to reduce exercise/sports performance. To clarify the effect of heat stress on motor preparation processing using electroencephalography (EEG), subjects performed two types of voluntary isometric exercise before (normothermia) and during heat stress on different days. Fifteen volunteers performed contingent negative variation (CNV) trials in Experiment 1, and fourteen volunteers performed movement‐related cortical potential (MRCP) trials in Experiment 2, while eleven subjects performed both trials. Whole body heating via a water‐perfused suit increased the esophageal temperature by 1.52 ± 0.14 °C in Experiment 1 and 1.40 ± 0.10 °C in Experiment 2. The mean amplitudes of the middle‐ and late‐CNV at Cz and Pz during heat stress were significantly reduced relative to those in normothermic trials (middle CNV, −3.3 ± 2.8 to −0.5 ± 3.2 μV at Cz, −3.8 ± 2.8 to −1.6 ± 3.0 μV at Pz; late CNV, −5.9 ± 3.5 to −3.1 ± 3.1 μV at Cz, −6.6 ± 2.9 to −3.7 ± 2.8 μV at Pz, P< 0.05 for each). However, in Experiment 2, there were no significant differences between normothermia and heat stress regarding the mean amplitudes of MRCPs including the Bereitschaftspotential (BP) and negative slope (NS′). These results suggest that mild hyperthermia influences cognitive processing being reflected by CNV with stimulus‐triggered movement, rather than motor‐related processing reflected by MRCPs related to self‐initiated movement.Support or Funding InformationJapan Society for the Promotion of Science 18H03166