[Research Review] Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Exploring the Relationship Between Clinical Medicine and Athletic Performance (Article 157)

Reference 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. Once plasma volume increases, 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 competitive relationship is greatly alleviated.

Core Temperature Regulation Adaptation Process

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 onset 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 becomes 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 scheduling additional passive heat exposure via hot baths/saunas after training in a mild environment
• Electrolyte Supplementation: Sweat rate increases substantially during the adaptation period; sodium and water intake frequency should be increased to avoid the risk of hyponatremia
• Progressive Approach: Exercise intensity should be reduced during the early phase of heat acclimation training to avoid the risk of heat stroke from simultaneous spikes in core temperature and cardiovascular load
• Adaptation Decays: The effects of heat acclimation gradually diminish approximately 1-3 weeks after cessation of exposure; the main adaptation phase of a pre-race heat acclimation schedule should be completed within 2 weeks before the race

Common Scientific Q&A (FAQ)

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

A: It is most beneficial for athletes planning to compete in hot, humid environments. If the race location has a cool climate, the marginal benefit of heat acclimation decreases, 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 it cannot fully replace the training-specific adaptation that occurs 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 acclimation and plasma volume regulation mechanisms.
2. Scandinavian Journal of Medicine & Science in Sports — Literature on the effects of heat acclimation training interventions in endurance athletes.

Related Reading

• 【Research Review】Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Exploring the Relationship Between Clinical Medicine and Athletic Performance (Article 394)
• 【Research Review】Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Frontiers in Exercise Physiology Research Progress (Article 1423)
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