【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 (No. 652)

Source Journal 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 simultaneously improves “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 substantially 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 sweating threshold temperature 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 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 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 fluid intake frequency should be increased to avoid the risk of hyponatremia
• Progressive Approach: Exercise intensity should be reduced during the initial heat adaptation training to avoid the risk of heat stroke from simultaneously spiking core temperature and cardiovascular load
• Adaptation Decays: Heat adaptation effects gradually diminish approximately 1-3 weeks after cessation of exposure; the main adaptation phase of pre-race heat acclimation should be scheduled within 2 weeks before the competition

Common Research 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 venue has a cool climate, the marginal benefits of heat adaptation decrease, but plasma volume expansion itself still provides positive assistance to general endurance performance.

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

A: It can serve as an auxiliary 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 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.

Related Topic 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 (No. 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 (No. 964)
• 【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 (No. 55)
• 【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 (No. 223)