Collins, S., Sawyer, J., Gregory, S., Van Langen, D., Dietel, K., Matthews, T., & Paolone, V. (June 02, 2010). Influence of rate of rehydration on exercise performance in dehydrated males. Presentation 1685 at the 2010 Annual Meeting of the American College of Sports Medicine, Baltimore, Maryland; June 2-5.

This study observed the influence of the rate of rehydration on exercise performance on dehydrated males (N = 10) in a thermoneutral environment. Each S performed three testing sessions, including an O2peak test and two one-hour cycle rides (75% O2peak) while dehydrated. During each of the cycle rides, Ss were administered a randomly selected rehydration strategy (4 x 250 ml every 15 minutes or 2 x 500 ml at 30 and 45 minutes). Numerous variables were collected throughout the course of each trial. Body Temperature and physiological variables were collected every five minutes.

Significant and expected changes over time existed for temperature and physiological data. No significant differences for the weights or thermoregulatory data were revealed. A significant interaction for percent change in plasma volume as well as significant differences for hematocrit and cell volume were reported, indicating the possible benefits of rehydration early in an exercise bout rather than later when dehydrated.

Implication. Enhancements or maintenance of plasma volume and hematocrit concentrations may indicate a benefit to performance by limiting cardiovascular strain during exercise. Increases in hematocrit and cell volume would have negatively affected cardiovascular performance through increased blood viscosity. By maintaining hematocrit levels and plasma volume through rehydration, performance may be enhanced through decreasing cardiovascular strain over the duration of exercise. It is prudent to hydrate early in an extended performance rather than waiting until the point where a need is perceived or a substantial amount of fluid has been lost.

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