Author(s): BURR, J., OPPITZ, E., TSIOROS, S.L., MCCRONE, J.C., ROBERTSON, A.A., CHEUNG, C.C., SCHMIDT, A., PEDERBY, M.D., MCCARTHY, D.G., Institution: UNIVERSITY OF GUELPH, Country: CANADA, Abstract-ID: 1561

INTRODUCTION:
Mild dehydration (~1-3% body mass loss) impairs performance in endurance and team sports. Specific to ice hockey, dehydration impairs repeated sprint ability, decision making, and markers of in-game performance. This assertion is largely drawn by contrasting complete fluid abstention with optimal hydration, which does not test whether improved hydration enhances performance, reflect typical drinking behaviours of athletes, or account for blinding or placebo/nocebo effects. This study tested whether optimizing hydration by correcting for observed losses could mitigate declines in performance amongst athletes who mildly dehydrated compared to a subgroup of athletes who already optimally hydrated.
METHODS:
Eighteen varsity athletes (10 female) completed performance tests before and after two standardized practices. In practice one (ad libitum hydration), athletes drank normally and hydration was tracked. Two groups were created based on body mass loss across the ad libitum hydration practice: >1%, intervention (n=10; 1.7%±0.3%); or <1%, control (n=8; 0.5%±0.3%). During the second practice (prescribed hydration), all athletes were informed they would receive optimal hydration so that no athlete lost >1% body mass. The intervention group ingested ~500 mL more water during prescribed vs. ad libitum hydration (790±230 vs. 310±170 mL, p<0.0001) and, by design, the control group was unchanged (800±260 vs. 690±150 mL, p=0.25). All athletes were informed that the hydration protocol would optimise hydration; however, only the intervention group improved hydration status. The control condition therefore accounted for expectancy effects and maintained blinding, and participants received no hydration feedback until study completion.
RESULTS:
Perceived on-ice fatigue was reduced during the prescribed vs. ad libitum hydration practice in the intervention group (6±1 vs. 5±1 of 10, p=0.003) but not control (4±1 vs. 4±1 of 10, p=0.6). The change across practice in 10-m sprint acceleration, velocity, power, or repeated 20-m sprint ability, assessed using 1080 Sprint (1080 Motion), was not different between hydration approaches in either group (p>0.14). A 15-m sprint involving a decision slowed across the ad libitum hydration practice and this was mitigated during prescribed hydration in both groups (0.6±2.8% vs. 2.0±2.8%, p=0.01). When comparing pre-practice performance tests, no order effects were observed on any performance drill (p>0.16).
CONCLUSION:
Optimizing on-ice hydration reduced perceived fatigue only in athletes who improved hydration status. Informing athletes they would receive optimal hydration improved on-ice performance independent of whether hydration status was improved, suggesting a possible placebo influence. This blinded study design provides a framework for future research concerning dehydration and performance team sport.