Heat-acclimatization and pre-cooling: a further boost for endurance performance?

Area of Science:

• Sports Science
• Environmental Physiology
• Exercise Physiology

Background:

• Heat acclimatization (HA) improves endurance performance in hot conditions.
• Pre-cooling (PC) using methods like ice vests can enhance exercise capacity in the heat.
• The combined effects of HA and PC on self-paced endurance performance require further investigation.

Purpose of the Study:

• To investigate if pre-cooling (PC) following heat acclimatization (HA) can further enhance self-paced endurance performance in a hot environment.
• To assess the impact of PC and HA on pacing strategies, physiological responses, and perceptual ratings during cycling time trials.
• To determine the interaction between HA and PC on endurance performance and associated responses.

Main Methods:

• 13 male triathletes completed two 20-km cycling time trials (TT) in a hot environment (35°C, 50% RH).
• Trials were conducted before and after an 8-day training camp, with and without ice vest pre-cooling (PC).
• Pacing, physiological (cardio-thermoregulatory), and perceptual responses were measured during each TT.

Main Results:

• Both HA and PC individually increased power output (PO) significantly.
• HA induced a very large increase in PO (+28 W), while PC induced a moderate increase (+10 W) before HA.
• Post-HA, the additional effect of PC on PO was unclear (+4 W), though PC transiently aided pacing in the first half of the TT and improved thermal comfort.

Conclusions:

• Pre-cooling improves 20-km TT performance in unacclimatized athletes.
• An 8-day heat acclimatization period attenuates the performance-enhancing effect of pre-cooling.
• Converging physiological responses to HA and PC may explain the reduced effectiveness of PC after HA, though perceptual benefits persist.