Precooling and Warm-Up Effects on Time Trial Cycling During Heat Stress

Area of Science:

• Exercise physiology
• Environmental physiology
• Sports science

Background:

• Heat stress significantly impairs endurance exercise performance.
• Precooling and warm-up are potential strategies to mitigate heat stress.
• Combining these strategies may offer synergistic benefits or drawbacks.

Purpose of the Study:

• To test if combining precooling and warm-up improves cycling time trial performance in hot conditions compared to each strategy alone.
• To evaluate the effects of precooling and warm-up on physiological responses during exercise in the heat.

Main Methods:

• Nine healthy men completed three 16.1-km cycling time trials in 33°C heat.
• Interventions included precooling alone (PREC), warm-up alone (WU), and combined precooling plus warm-up (COMBO).
• Physiological measures such as core temperature, skin temperature, heart rate, and sweat rate were recorded.

Main Results:

• Precooling alone (PREC) resulted in lower core and skin temperatures compared to warm-up (WU) and the combined (COMBO) condition during initial exercise stages.
• Combined (COMBO) showed lower core temperature than WU for the first 4 km.
• No significant differences in 16.1-km time trial performance were observed between PREC, WU, and COMBO (31.9 ± 1.9 min, 33.1 ± 2.9 min, and 32.6 ± 2.7 min, respectively).

Conclusions:

• Precooling, with or without warm-up, effectively reduced thermal strain during exercise in the heat.
• Neither precooling alone nor the combination with warm-up significantly improved cycling time trial performance.
• Further research may be needed to optimize combined strategies for heat adaptation in endurance athletes.