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Water budget during ultra-endurance exercise
1Department of Physiology, University of the Witwatersrand, Parktown, South Africa.
Medicine and Science in Sports and Exercise
|December 31, 1997
Summary
Athletes lose significant water during ultra-endurance events, but water intake and metabolic processes nearly compensate for losses. Despite nearly replacing total water loss, body mass still decreases, highlighting the importance of hydration strategies for endurance athletes.
Area of Science:
- Sports Science
- Exercise Physiology
- Human Metabolism
Background:
- Ultra-endurance events, such as triathlons, impose significant physiological demands on athletes.
- Understanding water balance is crucial for optimizing performance and health in extreme physical activities.
Purpose of the Study:
- To quantify water gains and losses in male triathletes participating in an ultra-endurance event.
- To assess the contribution of exogenous and endogenous sources to total water balance.
- To determine the relationship between water balance and body mass changes post-exercise.
Main Methods:
- Measurement of sweat rate, urine output, and respiratory water loss.
- Quantification of water intake from beverages and food.
- Estimation of endogenous water production from carbohydrate and fat metabolism, and glycogen utilization.
Main Results:
- Total water loss averaged 1069 g.h-1, primarily due to sweat (940 g.h-1).
- Total water gain averaged 940 g.h-1, with exogenous sources (fluid and food intake) contributing the most.
- Body weight decreased by 4.61%, with total water gains replacing nearly 90% of total water losses.
Conclusions:
- Endogenous water production significantly contributes to rehydration during ultra-endurance events.
- Despite substantial water replacement, a net body mass loss occurs, underscoring the challenge of complete rehydration.
- Optimal hydration strategies should consider both fluid intake and the body's metabolic water production.