Individuals with higher risk perception report more heat stress and thirst after hiking in a hot and dry environment without other differences in physiological measurements.

This study investigated the relation between physiological markers associated with exercise (measured and self-reported) and self-reported risk perception (RP) among hikers in extremely hot environments. Participants (n=340, 43% female, 40.1±12.9 years) were recruited at hiking trails during two hot and dry summers in Phoenix, Arizona, USA. Participants completed an onsite exit questionnaire, and a subsample participated in physiological testing. Outcomes were stratified for participants with a high and low RP. Self-reported heat stress (3.0, IQR: 3.0–5.3 vs. 3.0, IQR: 2.0–4.0, p=0.001) and thirst (38.0, IQR: 23.0–52.0 vs. 31.0, IQR: 19.0-47.8, p=0.039) were significantly higher in hikers with high RP vs. low RP scores, respectively. However, perceived exertion (6.0, IQR: 6.0–12.0), body temperature (35.3℃, IQR: 34.2–35.0), urine specific gravity (1.021, IQR: 1.015–1.026), and fitness level (48.6, IQR: 41.9–56.7), were not associated with RP scores (p≥0.100). Most participants considered ambient temperature and hike duration when planning fluid intake, however, although the high-risk group reported these safety behaviors more frequently, no group difference was seen in hydration status, amount of fluid carried (1000 mL, IQR: 500–1999), or fluid consumed (591 mL, IQR: 355–1000). In conclusion, RP may influence how individuals anticipate and respond to environmental challenges, such as reporting more heat stress and thirst in those with a high RP. Greater awareness regarding a heat safety campaign and precautionary behaviors were seen in high RP, but this did not translate into measurable differences in other physiological outcomes or actual hydration practices.