Environmental, physiological, perceptual, and behavioral predictors of mean and final km paces during a laboratory-based self-paced 10 km run in hot conditions

Endurance performance is regulated by integrated physiological, perceptual, and behavioral mechanisms, and is markedly impaired by environmental heat stress. However, how heat stress influences this multifaceted regulation of performance merits further investigation. This study aimed to identify predictors of mean and final km paces during a laboratory-based run in hot conditions. We analyzed 75 records from recreational athletes who ran 10 km as fast as possible at 33 °C. The independent variables included maximal oxygen uptake (VO_2MAX), whole-body sweat loss, fan-generated airflow, wet-bulb globe temperature (WBGT), change in core temperature (ΔT_CORE: entire exercise and its first five km), heart rate (HR), rating of perceived exertion (RPE), pacing strategy, biological sex, thermal comfort, the core-to-skin temperature difference, and percentage change in body mass (Δ% body mass). These independent variables were selected a priori based on theoretical models that explain pacing regulation in an integrative manner. The dependent variables were the mean and final km paces (min/km), and predictors were analyzed using hierarchical multiple linear regression. Mean pace was best predicted by air velocity (β = −0.494), ΔT_CORE (β = −0.456), VO_2MAX (β = −0.387), WBGT (β = 0.294), ΔT_CORE 0–5 km (β = 0.323), and Δ% body mass (β = −0.191), with the model explaining 54.3 % of the dependent variable's variance. Final km pace was best predicted by the adoption of a negative-split pacing strategy (β = 0.387), followed by HR (β = −0.206) and RPE (β = −0.188), with the model explaining 30.3 % of the dependent variable's variance. The current findings reinforce the notion that the regulation of mean and final km paces integrates physiological, environmental, behavioral, and perceptual mechanisms. Our findings also indicate that interventions to improve athletes' performance in hot conditions should combine aerobic fitness development, early T_CORE control, optimized airflow and hydration, and RPE-guided conservative/negative-split pacing.