[Research Review] Study on Heat Acclimation Training and Its Effects on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: Exploring the Relationship Between Clinical Medicine and Athletic Performance (Article 415)

Source Reference: 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. With increased plasma volume, under the same cardiac output, skin blood flow and muscle blood flow can both receive more adequate supply simultaneously—this is precisely the key to how heat adaptation can improve both “heat dissipation capacity” and “athletic performance”: before plasma volume expansion, the body must compete between “muscle blood supply” and “skin heat dissipation blood supply”; after adaptation, this competition is significantly alleviated.

The Adaptation Process of Core Temperature Regulation

The complete heat acclimation 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 begins 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 is smaller, and resting heart rate decreases

Heat Acclimation Days and Physiological Indicator Changes (Illustrative)

Key Scientific Conclusions and Practical Recommendations

• Exposure Methods: Adaptation can be accelerated through actual hot-environment training, or by arranging additional passive heat exposure via hot baths/saunas after training in a temperate environment
• Electrolyte Supplementation: Sweat rate increases substantially during the adaptation period; sodium and fluid intake frequency should be increased to avoid the risk of hyponatremia
• Progressive Approach: Exercise intensity should be reduced during the initial phase of heat acclimation training to avoid the risk of heat stroke from a simultaneous surge in core temperature and cardiovascular load
• Adaptation Fades: The effects of heat acclimation gradually diminish approximately 1-3 weeks after cessation of exposure; the primary acclimation period in a pre-race heat training plan should be scheduled within 2 weeks before the competition

Common Scientific Q&A (FAQ)

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

A: The benefits are most pronounced for athletes planning to compete in hot and humid environments. If the race location has a cool climate, the marginal benefits of heat acclimation diminish, but plasma volume expansion itself still provides positive benefits for general endurance performance.

Q: Can saunas replace actual hot-environment training?

A: They can serve as a supplementary method—passive heat exposure can indeed induce partial adaptation responses—but they cannot fully replace the training-specific adaptations that occur when “exercise + heat” occur simultaneously. It is recommended to combine both approaches.

References and Academic Citations

1. Journal of Applied Physiology — Research directions related to heat acclimation 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.

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