5 k Cycling Performance Under Hot-dry Vs Warm-humid Conditions With Matched WBGT

Previous research demonstrates that heat stress impairs athletic performance, impacting effectiveness and outcomes in competitive events. Wet-bulb globe temperature (WBGT) is widely recommended for assessing heat stress in athletic events because it integrates temperature, humidity, wind, and solar radiation to provide a comprehensive measure of environmental stress. However, the impact of varying temperature and humidity levels on performance with matched WBGT has not yet been evaluated. PURPOSE: Evaluate 5 k cycling performance in two different environmental conditions, hot-dry (HD: 39.2 °C, 30% RH) and warm-humid (WH: 34.2 °C, 55% RH), with matched WBGT (30 °C) to determine the impact of physiological strain and performance outcomes. METHODS: Nine healthy, active, non-heat-acclimatized males (29 ± 7 y, 77.4 ± 9.3 kg, 178.9 ± 10.5 cm, 51.9 ± 5.3 mL/kg/min VO2peak), completed two randomized, crossover trials. Each trial involved 60 minutes of cycling at 55% VO2peak, followed by a 5 k time trial with constant 3% incline. Performance was assessed using average power, speed, and finish time during the 5 k time trial. To assess physiological strain, maximal heart rate and rectal temperature change were monitored during the 5 k time trial. Data were analyzed using paired samples t-tests with significance set to p < .05. RESULTS: There were no significant differences in average power (HD: 214.1 ± 50.7 W, WH: 225.5 ± 49.3 W, p = .39) speed (HD: 18.6 ± 3.5 mph, WH: 19.5 ± 3.3 mph, p = .37) or finish time (HD: 16.67 ± 3.46 min, WH: 15.81 ± 2.72 min, p = .457) between the HD and WH conditions. Physiological responses, including max heart rate (HD: 186 ± 7 bpm, WH: 187 ± 5 bpm, p = .68) and the change in rectal temperature (HD: 0.38 ± 0.18 °C, WH: 0.21 ± 0.17 °C, p = .10) during the 5 k showed no significant differences. CONCLUSION: When WBGT was matched, 5 k cycling performance and physiological responses were minimally impacted in HD compared to WH conditions. These findings indicate that similar 5 k cycling performance across diverse environments supports WBGT as an effective single metric for assessing heat stress in short-duration events.