Palmer, G. S., van Someren, K. A., & Backx, K. (2001). No effect of fluid volume on performance during 1-hour cycling time trial in thermoneutral environment. Medicine and Science in Sports and Exercise, 33(5), Supplement abstract 1453.

The effects of different fluid volumes during a 1-hr cycling time trial in a thermoneutral environment were investigated in trained male cyclists (N = 8). Following consumption of a bolus of 6 ml/kg (6.4% CHO), and immediately following a 5-minute warm-up, each S performed the time trial on four occasions. The first trial allowed fluid ingestion on demand at 15-20, 30-35, and 45-50 minutes into the trial. Thereafter, trials required high, moderate, and low fluid consumption at the same time intervals. In all trials, total CHO intake was maintained at 58 gm.

There were no differences in performance (distance covered or mean power) or physiological responses (heart rate, temperature, sweat loss) between trials. Ss rated stomach fullness higher in the high fluid consumption trial.

Implication. The ingestion of a CHO beverage before one hour of concerted exercise is sufficient for performance. Further fluid ingestion does not improve performance. Being well hydrated before a performance is the most important aspect of fluid intake in tasks of one-hour.

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