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Erschienen in:
18.11.2016 | Original Article
Separate and combined effects of exposure to heat stress and mental fatigue on endurance exercise capacity in the heat
Erschienen in: European Journal of Applied Physiology | Ausgabe 1/2017
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Purpose
This study investigated the effects of exposure to pre-exercise heat stress and mental fatigue on endurance exercise capacity in a hot environment.
Methods
Eight volunteers completed four cycle exercise trials at 80% maximum oxygen uptake until exhaustion in an environmental chamber maintained at 30 °C and 50% relative humidity. The four trials required them to complete a 90 min pre-exercise routine of either a seated rest (CON), a prolonged demanding cognitive task to induce mental fatigue (MF), warm water immersion at 40 °C during the last 30 min to induce increasing core temperature (WI), or a prolonged demanding cognitive task and warm water immersion at 40 °C during the last 30 min (MF + WI).
Results
Core temperature when starting exercise was higher following warm water immersion (~38 °C; WI and MF + WI) than with no water immersion (~36.8 °C; CON and MF, P < 0.001). Self-reported mental fatigue when commencing exercise was higher following cognitive task (MF and MF + WI) than with no cognitive task (CON and WI; P < 0.05). Exercise time to exhaustion was reduced by warm water immersion (P < 0.001) and cognitive task (P < 0.05). Compared with CON (18 ± 7 min), exercise duration reduced 0.8, 26.6 and 46.3% in MF (17 ± 7 min), WI (12 ± 5 min) and MF + WI (9 ± 3 min), respectively.
Conclusions
This study demonstrates that endurance exercise capacity in a hot environment is impaired by either exposure to pre-exercise heat stress or mental fatigue, and this response is synergistically increased during combined exposure to them.