Influence of Exercise Heat Acclimation Protocol Characteristics on Adaptation Kinetics: A Quantitative Review With...

Area of Science:

• Environmental Physiology
• Exercise Science
• Human Adaptation

Background:

• The specific influence of heat acclimation (HA) protocol characteristics on adaptation speed and exercise capacity in heat remains insufficiently understood.
• Variations in HA protocols, including exposure frequency, duration, environmental conditions, and methodology, likely affect physiological responses.

Purpose of the Study:

• To investigate how different heat acclimation (HA) protocol characteristics influence adaptation kinetics and exercise capacity in hot environments.
• To quantify the effects of HA on physiological markers and performance metrics.

Main Methods:

• Utilized Bayesian multilevel regression models to analyze data from 211 studies.
• Included predictors such as number of exposures, exposure duration, ambient temperature, water vapor pressure, and HA approach.
• Presented results as posterior means with 90% credible intervals.

Main Results:

• HA significantly reduced resting and end-exercise heart rate and core temperature, while expanding plasma volume.
• Whole-body sweat rate (WBSR), time to exhaustion, and incremental exercise time increased post-HA.
• Specific protocol adjustments, like additional exposures or longer durations, further enhanced adaptations such as hemoglobin mass and plasma volume expansion.

Conclusions:

• Heat acclimation (HA) protocol characteristics critically influence adaptive responses and exercise performance in the heat.
• Findings suggest that HA protocols can be tailored to optimize specific adaptations for improved heat tolerance and performance.
• A predictive tool for estimating HA adaptations based on protocol characteristics is available.