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Plasma hormonal responses at graded hypohydration levels during exercise-heat stress
Journal of Applied Physiology (Bethesda, Md. : 1985)
|December 1, 1985
Summary
This study shows that dehydration significantly impacts hormonal responses during exercise in heat. Increased hypohydration intensifies plasma cortisol, renin activity, and aldosterone levels.
Area of Science:
- Exercise Physiology
- Endocrinology
- Environmental Physiology
Background:
- Dehydration affects physiological responses during exercise.
- Hormonal regulation is crucial for thermoregulation and fluid balance.
Purpose of the Study:
- To investigate the effects of graded hypohydration on hormonal responses during exercise in a hot environment.
- To determine the relationship between dehydration intensity and hormonal changes.
Main Methods:
- Six heat-acclimated males underwent graded hypohydration (3%, 5%, 7% body weight loss).
- Subjects performed light exercise in a hot environment (49°C, 20% RH).
- Blood samples were collected pre-exercise and during exercise to measure plasma cortisol (PC), plasma renin activity (PRA), and plasma aldosterone (ALD).
Main Results:
- Plasma cortisol (PC) levels increased with hypohydration intensity, rising significantly up to 7% dehydration.
- Plasma renin activity (PRA) and plasma aldosterone (ALD) levels were elevated by hypohydration and exercise in heat, with significant correlations up to 5% dehydration.
- Exercise in heat increased ALD, while PRA was primarily affected by hypohydration.
Conclusions:
- Hypohydration significantly alters hormonal responses to exercise in heat.
- Cortisol, renin activity, and aldosterone are sensitive indicators of dehydration stress during exercise.
- The findings highlight the physiological challenges of exercising in hot conditions while dehydrated.