【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: An International Scientific Literature Translation and Review Report (Article 55)

Reference Journal Source: Journal of Applied Physiology • International Scientific Research 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 acclimation simultaneously improves “heat dissipation capacity” and “exercise performance”: before plasma volume expansion, the body must compete between “muscle blood supply” and “skin heat-dissipation blood supply”; after acclimation, this competition is substantially alleviated.

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 onset 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 becomes smaller, and resting heart rate decreases

Heat Acclimation Days and Physiological Indicator Changes (Illustrative)

Core Research Conclusions and Practical Recommendations

• Exposure Methods: Adaptation can be accelerated through actual hot-environment training, or by scheduling additional hot baths/sauna passive heat exposure after training in a mild environment
• Electrolyte Supplementation: Sweat rate increases substantially during the adaptation period; sodium and water supplementation frequency should be increased to avoid the risk of hyponatremia
• Progressive Approach: Exercise intensity should be reduced during the initial heat acclimation training phase to avoid the risk of heat stroke from simultaneous spikes in core temperature and cardiovascular load
• Adaptation Decays: Heat acclimation effects gradually diminish approximately 1-3 weeks after cessation of exposure; the primary acclimation period of a pre-race heat acclimation schedule should be completed within 2 weeks before race day

Common Research Q&A (FAQ)

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

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

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

A: They can serve as an adjunct; 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 use both in combination.

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】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: An International Scientific Literature Translation and Review Report (Article 223)
• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: An International Scientific Literature Translation and Review Report (Article 652)
• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: An International Scientific Literature Translation and Review Report (Article 751)
• 【Research Review】Effects of Heat Acclimation Training on Plasma Volume Expansion and Core Temperature Adaptation in Marathon Runners: An International Scientific Literature Translation and Review Report (Article 964)