Optimizing Heat Acclimation for Endurance Athletes: High- Versus Low-Intensity Training.

Area of Science:

• Exercise Physiology
• Environmental Physiology
• Sports Science

Background:

• Heat acclimation (HA) is crucial for endurance athletes training in hot conditions.
• Understanding the impact of training intensity during heat exposure and taper is vital for optimizing performance.
• Previous research has not fully elucidated the effects of varying training intensities during heat acclimation and subsequent taper.

Purpose of the Study:

• To investigate the effects of high-intensity versus low-intensity training in the heat.
• To examine the impact of the ensuing taper period in the heat on endurance performance.
• To compare these effects against training in thermoneutral conditions.

Main Methods:

• 19 well-trained triathletes were divided into two heat acclimation groups (low-intensity [HA-L] and high-intensity [HA-H]) and one control group.
• Training occurred over 5 days, followed by a 1-week taper, all in specified heat or thermoneutral conditions.
• 20-km cycling time trials were conducted pre-exposure, mid-exposure, and post-taper.

Main Results:

• Low-intensity heat training (HA-L) progressively improved performance and showed physiological signs of heat acclimation.
• High-intensity heat training (HA-H) led to initial overreaching, decreased performance mid-study, but performance recovered post-taper.
• While HA-H induced adaptations, its performance benefits at the end of the taper were not superior to the control group.

Conclusions:

• High-intensity heat training can rapidly induce functional overreaching in non-acclimatized athletes.
• The performance supercompensation following high-intensity heat training and taper was limited.
• Athletes and coaches must closely monitor training load during heat preparation, reducing intensity if overreaching signs appear.