<b>Effects of passive heat exposure and exercise on executive function, thermoregulation and cerebral oxygenation</b>

This study aimed to examine the effects of passive heat exposure and exercise on executive function (EF), subjective perceptions, physiological measures, and cerebral oxygenation. Sixteen subjects underwent four trials: two sessions in hot environmental conditions (~35°C), with and without exercise intervention (HE, HNE), and two sessions in moderate environmental conditions (~25°C), with and without exercise intervention (ME, MNE). In each session, the subjects completed EF tasks prior to and following 1 h of passive rest or moderate-intensity cycling intervention. Passive exposure to a hot environment increased the core temperature (Tcore), mean skin temperature (Tskin), heart rate (HR), thermal sensation (TS), and rating of perceived exertion (RPE) as well as decreased the thermal comfort (TC). Compared to passive heat exposure, exercise in a hot environment further increased physiological indicators and subjective feelings, but decreased the TS. Moreover, passive heat exposure increased the reaction time (RT) of the More-odd shifting task and the 2-back task; while it decreased the oxygenation difference during the More-odd shifting task. The RT of the More-odd shifting task, 2-back task, and Stroop task in incongruent conditions were decreased in a hot environment with exercise, while the oxyhaemoglobin (HbO) and oxygenation difference during the Stroop task in incongruent conditions were increased. These findings indicate that passive heat exposure changes the Tcore and Tskin, which alters the subjective feelings and impair the EF performance. Exercise inhibits the deterioration of subjective feelings and ameliorated the impairment of EF performance via passive heat exposure. Furthermore, the effects of heat exposure and exercise on EF performance may be related to changes in pre-frontal cortex oxygenation.