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The hyponatremia of exercise
1Dept. of Physiology, University of Cape Town Medical School, Observatory, South Africa.
International Journal of Sport Nutrition
|September 1, 1992
Summary
Symptomatic exercise-induced hyponatremia, a dangerous condition causing severe brain dysfunction, occurs in endurance athletes who overhydrate. Avoiding excessive fluid intake is key to prevention.
Area of Science:
- Sports Medicine
- Exercise Physiology
- Endocrinology
Background:
- Exercise-associated hyponatremia can manifest in symptomatic and asymptomatic forms.
- Symptomatic cases involve severe cerebral dysfunction, including seizures and coma, particularly in less competitive athletes during prolonged endurance events (>5 hours).
- Symptomatic hyponatremia develops when excess fluid retention surpasses 2-3 liters.
Purpose of the Study:
- To explore the potential etiologies and preventative strategies for symptomatic exercise-induced hyponatremia.
Main Methods:
- Review of clinical presentations and proposed pathophysiological mechanisms of exercise-associated hyponatremia.
- Analysis of fluid balance and electrolyte shifts during prolonged exercise.
Main Results:
- Symptomatic hyponatremia is linked to excessive fluid intake (overhydration) in endurance athletes.
- Multiple underlying pathologies may contribute, including inappropriate antidiuretic hormone (ADH) secretion, extracellular fluid volume dysregulation, and sodium translocation into a 'third space'.
- The exact etiology remains unknown, likely involving a combination of factors.
Conclusions:
- Avoiding overhydration is the most reliable method for susceptible individuals to prevent symptomatic exercise-induced hyponatremia.
- Ingestion of sodium chloride solutions at physiologically significant concentrations may help mitigate the 'third space' effect.