Despite the predominance of research on physical performance in the heat, many activities require high cognitive functioning for optimal performance (i.e. decision making) and/or health purposes (i.e. injury risk). Prolonged periods of demanding cognitive activity or exercise-induced fatigue will incur altered cognitive functioning. The addition of hot environmental conditions will exacerbate poor cognitive functioning and negatively affect performance outcomes. The present paper attempts to extract consistent themes from the heat-cognition literature to explore cognitive performance as a function of the level of heat stress encountered. More specifically, experimental studies investigating cognitive performance in conditions of hyperthermia, often via the completion of computerised tasks (i.e. cognitive tests), are used to better understand the relationship between endogenous thermal load and cognitive performance. The existence of an inverted U-shaped relationship between hyperthermia development and cognitive performance is suggested, and highlights core temperatures of ~38.5 °C as the potential 'threshold' for hyperthermia-induced negative cognitive performance. From this perspective, interventions to slow or blunt thermal loads and protect both task- and hyperthermia-related changes in task performances (e.g. cooling strategies) could be used to great benefit and potentially preserve cognitive performance during heat strain.

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Highlights d Training overload in endurance sport induces cognitive control fatigue d Training-induced fatigue is associated with reduced prefrontal cortex activity d Training-induced fatigue is associated with enhanced choice impulsivity d Excessive physical training and intellectual work induce similar cognitive fatigue