The effects of fluid ingestion on free-paced intermittent-sprint performance and pacing strategies in the heat

The purpose of this study was to examine the effects of fluid ingestion on pacing strategies and performance during intermittent-sprint exercise in the heat. Nine male rugby players performed a habituation session and 2x50-min intermittent-sprint protocols at a temperature of 31 degrees C, either with or without fluid. Participants were informed of a third session (not performed) to ensure that they remained blind to all respective conditions. The protocol consisted of a 15-m sprint every minute separated by self-paced bouts of hard running, jogging, and walking for the remainder of the minute. Sprint time, distance covered during self-paced exercise, and vertical jump height before and after exercise were recorded. Heart rate, core temperature, nude mass, capillary blood haematocrit, pH, lactate concentration, perceptual ratings of perceived exertion, thermal stress, and thirst were also recorded. Sprint times (fluid vs. no-fluid: 2.82 +/- 0.11 vs. 2.82 +/- 0.14) and distance covered during self-paced exercise (fluid vs. no-fluid: 4168 +/- 419 vs. 3981 +/- 263 m) were not different between conditions (P=0.10-0.98) but were progressively reduced to a greater extent in the no-fluid trial (7 +/- 13%) (d=0.56-0.58). There were no differences (P=0.22-1.00; d=<0.20-0.84) between conditions in any physiological measures. Perceptual ratings of perceived exertion and thermal stress did not differ between conditions (P=0.34-0.91; d <= 0.20-0.48). Rating of thirst after exercise was lower in the fluid trial (P=0.02; d=0.62-0.73). The present results suggest that fluid availability did not improve intermittent-sprint performance, however did affect pacing stategies with a greater reduction in distance covered of self-paced exercise during the no-fluid trial.