Fluid Balance in Hockey Players and the Effects of Mild Dehydration and Carbohydrate Ingestion on Skeletal Muscle Metabolism, Performance and Cognitive Function During Intermittent Sprint Cycling
This thesis evaluated fluid balance in ice hockey players during practices, and the effects of dehydration on muscle metabolism, performance and cognition during intermittent sprint cycling, designed to simulate ice hockey skating. Main hypotheses included: 1) Players would experience moderate dehydration (-2% body mass (BM)) during on-ice practices. 2) Moderate dehydration would increase skeletal muscle glycogenolysis and impair performance in period 3 of the laboratory-based sprint cycling protocol. 3) Staying well-hydrated by drinking water or a CES would decrease glycogenolysis vs. moderate dehydration in period 3. 4) Cognitive function and perception of effort (RPE), would be impaired following the protocol when players were moderately dehydrated vs. when they ingested a CES. On-ice hockey practices induced large sweat losses (1.8±0.1 L·hr-1) and players replaced ~2/3 of the fluid lost with water, resulting in dehydration of -0.7±0.1% BM with ~10% of players losing >-2% BM. Mild dehydration in the laboratory (-1.1-1.8% BM) did not affect performance, glycogenolysis or Tc in period 3 vs. WATER ingestion. CES ingestion increased glycogen use in period 3 (177.5±31.1 vs. 103.5±16.2 mmol·kg dm-1), and increased performance (151.0±8.0 vs. 144.1±8.7 kJ) vs. mild dehydration. Overall Tc (37.9±0.1 vs. 38.1±0.1°C), and RPE in period 3 were lower (16±1 vs. 18±1) with CES ingestion. Complex cognitive functions were improved after the protocol when subjects ingested a CES vs. moderate dehydration (-2.5% BM). CES ingestion reduced mean Tc (38.0±0.0 vs. 38.1±0.1°C), and improved performance (151.0±8.0 vs. 144.1±8.7 kJ) and RPE (17±1 vs. 18±0) in period 3 vs. dehydration. These findings suggest that ice hockey players are only at risk of mild dehydration (~1% BM), but ~10% of players experience moderate dehydration (>-2% BM) during practices in the field. Mild dehydration (1.1-1.8% BM loss) had little influence on skeletal muscle metabolism and performance vs. hydrating with water, but CES ingestion increased glycogen use and performance in period 3 vs. mild dehydration. CES ingestion also improved cognition vs. moderate dehydration. The combined effects of consuming a CES on glycogen use, cognitive function and performance in the laboratory suggest a role for CHO ingestion in maintaining ice hockey performance in the field.