Henkin, S. D., Silveira, M. M., Ribiero, J., & Meyer, F. (2006). Sweat rate and voluntary fluid intake of elite level swimmers. Medicine and Science in Sports and Exercise, 38(5), Supplement abstract 1511.

This investigation assessed sweat rate, voluntary fluid intake and fluid balance of swimmers during a training session. Male swimmers (N = 8) performed two swimming sessions of 6,000 m on two different days. Sessions were carried out in an indoor swimming pool (30°C water temperature). Before and after training, all Ss were weighed nude, they were asked to micturate and defecate if necessary prior to the measurements. Blood and urine were collected three minutes before and after the training session to assess urine specific gravity (Usg) and hematocrit (hct).During the first training session all Ss had free access to mineral water and during the second one (FD) to an orange flavored sport drink (Gatorade). Each S was provided with individually numbered bottles. All drink bottles were weighed before and after the training session. Sweat rate was obtained using the formula: [(pre-exercise body mass (g) - post-exercise body mass (g)) + fluid intake (ml)]/90 minutes.

Sweat rate was similar in both training sessions. Fluid intake was higher in the water group than in the sport drink group.

Implication. On average, Ss did not drink sufficient fluid during the training session with some incurring substantial fluid deficit. There were large interindividual differences regarding sweat rate, fluid balance, and drinking practices. The use of a sport drink was more efficient because Ss drank a smaller amount while keeping sweat rate and fluid balance similar to those who drank water.

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