The Effects of Heat Exposure on Cognitive Performance

Abstract

Abstract In addition to physical conditioning, successful sporting performance requires a level of perception coupled with efficiency and accuracy in movement. The FIFA World Cup is usually played during the summer months; therefore the aim of this study was to investigate the effects of heat exposure on cognitive performance. Three experiments were performed in an environmental chamber under hot (HOT: 50°C, 30% rH) and control (CON: 24°C, 30% rH) conditions. Exposure time ranged from 15 minutes to 4.5 hours. Subjects performed simple and complex cognitive tasks under different levels of thermal strain. Neuromuscular assessments were performed to assess neural drive and muscular force production. Central (Tcore) and skin (Tskin) temperatures were recorded along with subjective measures of thermal comfort (TC) and thermal sensation (TS). Hyperthermia had no impact upon attention tasks, however, impulsivity increased during sustained attention over prolonged periods. Significant increases in Tcore (>38.30°C) were associated with impaired complex cognitive task performance. The regular application of cold packs to the head limited the detrimental effects of hyperthermia upon short-term memory. However, rapid and substantial variations in Tskin of ∼3°C, independent of changes in Tcore, had similar detrimental effects upon cognitive task performance. Results suggest that reductions in complex cognitive performance with heat exposure occur via a decrement in motor cortical excitability when Tcore increases to ∼38.3°C, but they also originate from an additional cognitive load imposed by thermal strain and the resulting allesthesial Tskin variations; with both these factors acting as competing variables to the cognitive processes. The increase in Tcore with prolonged heat exposure impairs cognitive performance; however applying cold packs to the head can preserve these. Increases in Tskin during brief heat exposures appear to be a sufficient physiological response to alter the emotional state of individuals and impair effective decision-making. Hydration protocols and reducing exercise intensity and load can reduce the physiological strain. Strategies to minimise the ‘thermal shock’ of entering a warm environment should be developed to minimise the impact of subjective feelings of thermal discomfort upon cognitive performance.