Heat stress impacts affective processes and risk-taking behaviour.

The understanding of heat stress on human behaviour is critical due to increasing frequency of extreme heat events. Heat stress has been shown to detrimentally alter affective states and cognition, effects that are particularly critical for individuals exposed to heat conditions such as firefighters, medical personnel, and athletes. Therefore, this study examined how heat stress, exercise, and wearing firefighter protective gear interact to influence affect and decision-making. A sample of 36 healthy young males was assigned to either a passive, combined or heat-stress-free group. Subjective perceptions of vitality, fatigue, thermal comfort and sensation were assessed, controlling for body core-, skin temperature, relative humidity in the jacket, and heart rate. Additionally, participants performed the Balloon Analogue Risk Task and the Beads Task. Linear mixed models revealed that passive heat stress increased fatigue, whereas vitality was not directly sensitive to heat stress. Fatigue and vitality bidirectionally influenced each other independent of heat stress, while thermal perception altered both affective states. Increased risk-taking behaviour was observed under prolonged combined heat stress. No effects on reflection impulsivity were found. Findings highlight differential impacts of heat stress on affective processes that can bias risk-taking behaviour. Particularly under combined heat stress, individuals may be prone to potentially riskier behaviour, insights that should be tested towards ecological validity in future proposals.