Simple And Complex Cognitive Functions Under Exertional Heat Stress

Heat stress is a significant problem in the military services. This study investigated the effects of exertional heat stress on cognitive performance.

Forty unacclimated male soldiers performed exertional heat stress tests in cool (20 °C) and hot environments (40 °C). Cognitive performance was assessed using a computerized battery before and immediately after tests. Physical strain in cool conditions induced mild but significant deficits in accuracy in complex tests. The number of correct answers in the Matching to Sample Visual Search was reduced (92,18% correct answers before vs. 88,64 after; p<0,05) and also in the spatial part of the Pattern and Spatial Recognition Memory Test (85,25 vs. 8,75%; p<0,05). These decreases were more pronounced in hot conditions (92,38 vs. 84,31% in before and 84,21 vs. 73,42% in the latter test; ps<0,01 and <0,001, respectively). Exertional heat stress also impaired more simple cognitive functions. A significant decrease in accuracy (95,74 vs. 93,89%) and an increase in reaction time (300,32 vs. 315,00 ms) was observed in the Reaction Time test.

Strenuous physical activity in a hot environment induces mild cognitive deficits, especially in more complex tasks.