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Hyponatremia induced by exercise: a 24-hour endurance march study
E Galun1, I Tur-Kaspa, E Assia
1Department of Medicine A, Hadassah University Hospital, Ein Karem, Israel.
Mineral and Electrolyte Metabolism
|January 1, 1991
Summary
Prolonged endurance marching can lead to hyponatremia (low serum sodium) in fit individuals. Excessive water intake, not renal function, is the primary cause, suggesting hydration should match physiological needs.
Area of Science:
- Exercise Physiology
- Sports Medicine
- Renal Physiology
Background:
- Previous research linked prolonged physical stress to muscle enzyme activity.
- Several participants in prior studies experienced hyponatremia.
- This study investigates the link between endurance stress and hyponatremia development.
Purpose of the Study:
- To evaluate the effect of prolonged physical stress on hyponatremia development.
- To analyze physiological changes during endurance marching.
- To identify factors contributing to hyponatremia in athletes.
Main Methods:
- Seventeen physically fit males participated in a 24-hour endurance march.
- Serum sodium levels, blood/plasma volume, and creatinine clearance were monitored.
- Urinary sodium excretion and free water clearance were assessed.
Main Results:
- Serum sodium decreased significantly (142 to 135 mEq/l) during the march.
- Blood and plasma volumes increased, while creatinine clearance declined.
- Increased water intake correlated positively with the fall in serum sodium.
Conclusions:
- Hyponatremia occurs in normal subjects during endurance marching with high water intake.
- The renal system's diluting response is appropriate, but maximal dilution is not achieved.
- Water intake should be guided by physiological needs to prevent hyponatremia during prolonged physical stress.