[Research Review] Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Physiological Characteristics of Elite Athletes (Article 1408)

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 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 can be observed:

• The core temperature threshold for sweat initiation decreases (sweating begins earlier, 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 scheduling additional passive heat exposure via hot baths/saunas after training in a mild environment
• Electrolyte Supplementation: Sweat rate increases substantially during the acclimation 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 simultaneously spiking core temperature and cardiovascular load
• Adaptation Decays: The effects of heat acclimation gradually diminish approximately 1-3 weeks after cessation of exposure; the main acclimation period for pre-race heat training should be completed within 2 weeks before race day

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, 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 an auxiliary method — passive heat exposure can indeed induce partial adaptation responses, but it 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 on the effects of heat acclimation training interventions in endurance athletes.

Further Reading

• Research Review: Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Physiological Characteristics of Elite Athletes (Article 1318)
• Research Review: Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Physiological Characteristics of Elite Athletes (Article 1435)
• Research Review: Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Physiological Characteristics of Elite Athletes (Article 1177)
• Research Review: Study on Heat Acclimation Training for Marathon Runners: Plasma Volume Expansion and Core Temperature Adaptation — Latest Academic Literature Review and Training Practice (Article 259)