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Fluid and electrolyte balance during a cool weather marathon
1Department of Medicine, Institute of Pittsburgh, University of Pittsburgh School of Medicine, Pennsylvania.
The American Journal of Sports Medicine
|November 1, 1989
Summary
Marathon runners experienced significant changes in blood and urine electrolytes, including increased serum sodium and potassium, and decreased urinary sodium, despite cool race conditions. Weight loss was less than in warmer marathons.
Area of Science:
- Exercise Physiology
- Sports Medicine
- Clinical Chemistry
Background:
- Fluid and electrolyte balance is critical during endurance events like marathons.
- Understanding physiological responses to marathon running is essential for athlete health and performance.
- Previous studies often focus on marathons in warmer climates, leaving a gap in knowledge for cooler conditions.
Purpose of the Study:
- To investigate changes in blood, serum, and urine parameters related to fluid and electrolyte balance in marathon runners.
- To compare pre-race and post-race physiological markers in a marathon event.
- To assess the impact of cool weather conditions on marathon runner physiology.
Main Methods:
- Analysis of blood, serum, and urine parameters in 45 marathon runners (39 male, 6 female, mean age 39.3).
- Comparison of pre-race and post-race measurements.
- Data collection during the 1987 Pittsburgh Marathon run in rain at 46°F.
Main Results:
- Significant increases observed in serum sodium, potassium, blood urea nitrogen (BUN), creatinine, uric acid, creatine phosphokinase (CPK), protein, plasma renin, vasopressin, and urinary potassium.
- Significant decreases noted in body weight (mean 1.9 kg loss), blood pressure, and urinary sodium.
- No significant changes in serum chloride, serum glucose, or hemoglobin/hematocrit.
Conclusions:
- Marathon running, even in cool, wet conditions, induces significant alterations in fluid and electrolyte homeostasis.
- The observed physiological changes suggest a complex interplay of hydration status, exertion, and environmental factors.
- Weight loss was less pronounced than typically reported in warmer marathon conditions, indicating a potential influence of ambient temperature on dehydration levels.