Cognitive Functioning and Heat Strain: Performance Responses and Protective Strategies

Abstract

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.

Sports and environmental temperature: From warming-up to heating-up

“…A moderate increase in core temperature can initially improve cognitive function. 137 Conversely, the development of hyperthermia can impair cognitive function, 138,139 with the impairments being task and complexity dependent. [140][141][142][143][144] It has been suggested that the performance of cognitive tasks under heat stress deteriorates when the total cognitive resources are insufficient to support both the adequate completion of the task and processing of the thermal stress.…”

Per-Cooling (Using Cooling Systems during Physical Exercise) Enhances Physical and Cognitive Performances in Hot Environments. A Narrative Review

“…It seems that a slight increase in core temperature improves cognitive performance [92]. This improvement may result from an increase in arousal and cerebral blood flow [93].…”

“…However, as highlighted by Bandelow et al [94], when one's core temperature reaches 37.8 • C, the improvement in cognitive performance disappears. Thus, the authors speculated that heat strain overloads one's cognitive capacity when his or her core temperature exceeds this threshold [92]. More recently, Yeganeh et al, (2018) performed a meta-analysis and confirm that hyperthermia is accompagnied by a deterioration of cognitive performance and reported that the mean percentage decline in cognitive performance as the result of variation in temperature follows an inverted U-shape curve.…”

“…Cognitive performance improves with mild heat strain but is impaired in individuals with a high degree of hyperthermia [148]. Cooling strategies seem to enhance cognitive performance, which is impaired by heat strain [92]. It has been reported that external cooling serves to alleviate the alterations induced by hyperthermia, such as thermoregulatory responses, and may reduce the difficulties the brain faces in dealing with accumulating stressors (i.e., cognitive demand and increasing heat strain), thereby allowing an increase in attentional resources to enhance cognitive functioning [92].…”

Mapping the Health, Safety and Wellbeing Challenges of Firefighting to Wearable Devices

“…This included development of training and guidance for firefighters to recognise the physiological effects of heat on themselves and their colleagues and to know when to withdraw from danger (Meadows, 2016). But how does one recognise the onset of heat strain when symptoms include a decline in cognitive function (Schmit, 2017)?…”