CrossAcclimation and Endurance Performance Following Adaptation to Dry and Humid Heat
Study Details
This crossover study examined whether hot-dry or warm-humid heat acclimation improved endurance performance in the same environment and whether benefits transferred between conditions in trained male cyclists 🔍
Cyclists completed 30-min time trials in hot-dry conditions (42°C, 25% RH) and warm-humid conditions (33°C, 80% RH) before and after heat acclimation 🚴
The two environments were matched for wet-bulb globe temperature at ~31°C 🌡️
Key Findings
🔥 After dry-heat acclimation, mean power during the dry time trial improved by ~14 W
💧 After humid-heat acclimation, dry-condition power improved by ~6 W
📈 Dry-heat acclimation therefore produced a greater improvement in dry-condition performance than humid-heat acclimation
🌫️ In humid conditions, performance improved similarly after both acclimation strategies: ~12 W after humid-HA and ~12 W after dry-HA
🔄 This demonstrates meaningful cross-acclimation, with adapting to one heat environment improving performance in the other
🌡️ Rectal temperature during the dry time trial was lower after both acclimation protocols
🫀 Heart rate also tended to be lower after acclimation, particularly when athletes were tested in the environment they had adapted to
💦 Whole-body sweat rate increased after both protocols in both dry and humid testing conditions
📉 During the humid time trial, rectal temperature decreased after dry-HA but was essentially unchanged after humid-HA
🧩 Overall, both protocols improved thermoregulatory responses, but dry-heat acclimation appeared to provide the broader performance benefit
Conclusion
For endurance athletes preparing for competition in the heat, acclimation in either dry or humid conditions can transfer across environments, but hot-dry acclimation may offer a slight advantage when dry-heat performance is particularly important ✅
Reference
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