Horn, M., Stofan, J., Passe, D., & Murray, R. (2001). Perceptions of fluid intake and sweat loss during a ten mile race. Medicine and Science in Sports and Exercise, 33(5), Supplement abstract 1444.

Seasoned runners (M = 15; F = 3) were evaluated for their accuracy in estimating fluid consumption and sweat losses during a 10-mile race. In the race, Ss were given access to a sport beverage (6% CHO solution) at miles 2, 4, 6, and 8. Ingestion was voluntary to simulate race conditions. A questionnaire was completed after the race.

Only 30% of lost sweat was replaced, leaving the Ss dehydrated at the end of the race. Sweat loss was underestimated by 46% and fluid intake underestimated by 15%.

Ss were seasoned runners. Their inability to gauge fluid intake and sweat loss indicates the need to have a planned fluid replacement program for races. [It should be noted that some fluid is generated through the metabolism of fats. Thus, the total exogenous water intake does not have to exactly match the actual fluid loss.]

Implication. Seasoned runners underestimate fluid needs in races.

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