【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: Advances in Frontier Exercise Physiology Research (Article 1039)

Reference Journal Source: Journal of Applied Physiology • International Scientific Research Findings Review Series

This article explores the physiological mechanisms of heat acclimation training on plasma volume expansion and core temperature regulation adaptation in marathon runners.

Physiological Mechanisms of Plasma Volume Expansion

Repeated heat exposure stimulates the kidneys and endocrine system to release antidiuretic hormone and aldosterone, prompting the body to retain more water and sodium ions, thereby expanding plasma volume. After plasma volume increases, under the same cardiac output, skin blood flow and muscle blood flow can both receive more adequate supply simultaneously—this is the key to how heat adaptation improves both “heat dissipation capacity” and “athletic performance” at the same time: before plasma volume expansion, the body must compete between “muscle blood supply” and “skin heat-dissipation blood supply”; after adaptation, this competition is greatly alleviated.

Adaptation Process of Core Temperature Regulation

The complete heat adaptation process typically requires 10-14 days of repeated exposure. During the adaptation process, the following observations can be made:

• The core temperature threshold for sweat initiation decreases (sweating starts earlier, and the heat dissipation response becomes more sensitive)
• Sweat rate per unit time increases, but sodium ion concentration in sweat decreases (reducing electrolyte loss)
• At the same exercise intensity, the rise in core temperature becomes smaller, and resting heart rate decreases

Heat Adaptation Days and Physiological Indicator Changes (Illustrative)

Core Scientific Conclusions and Practical Recommendations

• Exposure Methods: Adaptation can be accelerated through actual hot-environment training, or by arranging additional hot baths/sauna passive heat exposure after training in a mild environment
• Electrolyte Supplementation: Sweat rate increases substantially during the adaptation period; the frequency of sodium and fluid intake should be increased to avoid the risk of hyponatremia
• Progressive Approach: Exercise intensity should be reduced during the initial phase of heat adaptation training to avoid the risk of heat stroke caused by core temperature and cardiovascular load spiking simultaneously
• Adaptation Fades: The effects of heat adaptation gradually diminish approximately 1-3 weeks after cessation of exposure; the pre-race heat adaptation schedule should be arranged so that the main adaptation period is completed within 2 weeks before the race

Common Research Q&A (FAQ)

Q: Is heat acclimation training suitable for all marathon runners?

A: The benefits are most pronounced for runners expected to compete in hot and humid environments. If the race location has a cool climate, the marginal benefits of heat adaptation decrease, but plasma volume expansion itself still has positive effects on general endurance performance.

Q: Can sauna use replace actual hot-environment training?

A: It can serve as a supplementary method. Passive heat exposure can indeed induce some adaptive responses, but it cannot fully replace the training-specific adaptations that occur when “exercise + heat” happen simultaneously. It is recommended to combine both approaches.

References and Academic Citations

1. Journal of Applied Physiology — Research directions related to heat adaptation and plasma volume regulation mechanisms.
2. Scandinavian Journal of Medicine & Science in Sports — Literature related to the effects of heat acclimation training interventions in endurance athletes.

Further Reading

• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: Physical Characteristics of Elite Athletes (Article 1000)
• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: Physical Characteristics of Elite Athletes (Article 1318)
• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: Advances in Frontier Exercise Physiology Research (Article 835)
• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: Advances in Frontier Exercise Physiology Research (Article 778)