The effects of isothermic heat acclimation on simple and complex cognitive performance in the heat

Longer heat acclimation (HA) protocols more effectively improve physical performance than shorter ones, but the effect of HA duration on cognitive performance remains unclear. Twelve participants performed a 45-min cycling heat stress test [(HST) 40%W_max; 40°C; 50% RH] on the first (HST₁), seventh (HST₇), and thirteenth (HST₁₃) day of testing with five consecutive days of isothermic HA (60-min; rectal temperature ~38.5°C) between each HST. Simple (five-choice reaction time [RT]) and complex (spatial working memory [SWM]) tests were completed before and after each HST. Reaction and Movement times were slower before HST₁₃ than HST₁. Fewer errors were made in the SWM test before HST₁₃ in the 6- (0.0v2.7), 8- (1.8v7.6) and 12- (18v31) box tests and before HST₇ in the 6- and 8-box tests (1.9v7.6) compared to HST₁. Search strategy was improved before HST₇ (4.5v6.8) and HST₁₃ (4.3v6.8). Fewer errors were made in the 8-box test after HST₇ (1.6v8.8) and HST₁₃ (1.1v8.6). No other differences were observed (p > 0.05). HA improved performance in some of the more challenging tasks but had no effect on the most complex task (12-box) when physiological strain was highest. 10-days of HA was more effective than 5-days at improving some aspects of cognitive performance.