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The convective afterdrop component during hypothermic exercise decreases with delayed exercise onset
1Laboratory for Exercise and Environmental Medicine, Health, Leisure and Human Performance Research Institute, Faulty of Physical Education and Recreation Studies, Manitoba, Canada.
Aviation, Space, and Environmental Medicine
|February 6, 1998
Summary
Starting exercise after shivering has ended minimizes a second esophageal temperature drop after cold water immersion. This strategy reduces core-to-periphery heat loss during rewarming.
Area of Science:
- Sports Medicine
- Human Physiology
- Thermoregulation
Background:
- Cold water immersion causes a post-cooling esophageal temperature decrease (afterdrop).
- Exercise exacerbates this afterdrop more than shivering due to increased blood flow.
- The hypothesis is that delaying exercise until after the shivering afterdrop period minimizes a secondary drop.
Purpose of the Study:
- To investigate if commencing exercise after the shivering afterdrop period reduces a secondary esophageal temperature decrease.
Main Methods:
- Six subjects underwent three cooling trials in 8°C water.
- Esophageal temperature (Tes) was cooled to 35.3 ± 0.7°C.
- Rewarming methods included shivering alone, exercise alone, or exercise after a shivering afterdrop period.
Main Results:
- The initial afterdrop was significantly greater during exercise-only (1.1°C) than shivering-only (0.35°C) or shivering-exercise (0.45°C).
- A secondary afterdrop occurred during shivering-exercise (0.38°C).
- Initial rewarming rates were highest during exercise-only.
Conclusions:
- Continuing blood flow to shivering muscles contributes to the initial afterdrop.
- This blood flow diminishes the capacity for further core cooling during subsequent exercise.
- Exercising after the shivering afterdrop period appears to mitigate a secondary esophageal temperature decrease.