Decision-making under heat stress: Examining risk-taking and reflection impulsivity dynamics in the context of fatigue and vitality
Authors: Wälde Jannic , Amesberger Günter , Würth Sabine , Finkenzeller Thomas 
Published: September 2024

Introduction & Purpose
Acute high temperatures and physical activity induce physiological and psychophysiological stress (Périard et al., 2021). In athletes or professions like firefighting, core body temperatures often exceed 38.5 °C (Barr et al. 2010; Schmit et al., 2017). In this hyperthermic state, firefighters must make critical decisions impacting their safety and that of others. This study investigated the effects of heat stress (passive alone or combined with walking) on decision-making, focusing on reflective impulsivity and risk-taking behaviour. Secondly, we examined how both heat stressors (passive and active) impact subjective feelings of fatigue and vitality, and we explored how fatigue and vitality levels moderate these effects.
Methods
A sample of 36 healthy men (age: M = 26.94, SD = 3.25) participated in a repeated measures design with two experimental groups equipped with firefighting clothing. They were exposed to either passive heat stress (EG1) or a combination of passive and active heat stress (EG2), and a control group (CG) receiving no heat and physical stress. The Balloon Analogue Risk Task (BART) for risk-taking behaviour and the Beads Task (BT) for reflection impulsivity were applied to test cognitive performance. Thermal comfort (TC), thermal sensation (TS), rating-of-fatigue (Micklewright et al., 2017) and vitality (Buchner et al., 2022) were recorded every five minutes. Passive heat stress was induced through sauna exposure (30 min, 60 °C; 40% relative humidity). Additionally, the EG2 performed two subsequent walks on the treadmill to reach 38.5 °C body core temperature (à 20 min). Cognitive tests were performed before heat exposure (T1), after sauna (T2) and after subsequent activity in EG2 or after an equally long rest period in EG1 (T3). CG watched a documentary. Linear Mixed Models (LMM) analysed the effects of group and time on reflection impulsivity (Draws to Decision [DTD]), risk-taking behaviour (pumps), fatigue, and vitality.
Results
This study found no significant changes for EG1 and EG2 over time (p = .37, p = .43) in reflection impulsivity (DTD) or risk-taking behaviour (pumps) across different heat conditions (p = .58, p = .84) and interaction (p = .38, p = .93) compared to CG. Including random slopes for random effect of time across fatigue (p < .001) or vitality (p = .001) resulted in a significant deterioration of the model.
EG1 showed a significant increase in fatigue to T2 compared to the CG (p < .001) and to T3 (p < .001). In EG2, fatigue increased significantly to T3 (p = .022). In EG1, vitality decreased significantly to T2 (p = .002), and to T3 (p = .020). Including TC as random effect improved the overall model fit significantly (p = .005).
Discussion and Conclusion
Passive heat stress increased fatigue, and decreased vitality in EG1. However, walking in EG2 prevented this vitality decline, suggesting a protective effect of physical activity. Thermal comfort influenced both fatigue and vitality. Interestingly, neither reflective impulsivity nor risk-taking behaviour were affected by heat stress or changes in fatigue and vitality.
References
Barr, D., Warren, G., & Reilly, T. (2010): The thermal ergonomics of firefighting reviewed. Applied Ergonomics, 41(1), 161–172. https://doi.org/10.1016/j.apergo.2009.07.001
Buchner, L., Amesberger, G., Finkenzeller, T., Moore, S. R., & Würth, S. (2022). The modified German subjective vitality scale (SVS-GM): Psychometric properties and application in daily life. Frontiers in Psychology, 13, Article 948906. https://doi.org/10.3389/fpsyg.2022.948906
Micklewright, D., St Clair Gibson, A., Gladwell, V., & Al Salman, A. (2017). Development and validity of the rating-of-fatigue scale. Sports Medicine, 47(11), 2375–2393. https://doi.org/10.1007/s40279-017-0711-5
Périard, J. D., Eijsvogels, T. M. H., & Daanen, H. A. M. (2021). Exercise under heat stress: Thermoregulation, hydration, performance implications, and mitigation strategies. Physiological Reviews, 101(4), 1873–1979. https://doi.org/10.1152/physrev.00038.202
Schmit, C., Hausswirth, C., Le Meur, Y., Duffield, R. (2017): Cognitive functioning and heat strain: Performance responses and protective strategies. Sports Medicine, 47, 1289–1302. https://doi.org/10.1007/s40279-016-0657-z