Abstract des Autors

This study examined the influence of water ingestion on endurance capacity during submaximal treadmill running. Four men and four women with a mean (+/-S.E.) age of 21.4+/-0.7 years, height of 169+/-2 cm, body mass 63.1+/-2.9 kg and VO2max of 51.1+/-1.8 ml/kg/min, performed two randomly assigned treadmill runs at 70% VO2max to exhaustion. No fluid was ingested during one trial (NF-trial), whereas a single water bolus of 3.0 ml/kg body mass was ingested immediately pre-exercise and serial feedings of 2.0 ml/kg body mass were ingested every 15 min during exercise in a fluid replacement trial (FR-trial). Run time for the NF-trial was 77.7+/-7.7 min, compared to 103+/-12.4 min for the FR-trial. Body mass (corrected for water ingestion) decreased by 2.0+/-0.2% in the NF-trial and 2.7+/-0.2% in the FR-trial, while plasma volume decreased by 1.1+/-1.1% and 3.5+/-1.1% in the two trials respectively (N.S.). However, these apparent differences in circulatory volume were not associated with differences in rectal temperature. Respiratory exchange ratios indicated increased carbohydrate metabolism (73% vs 64% of total energy expenditure) and suppressed fat metabolism after 75 min of exercise in the NF-trial compared with the FR-trial (NF-trial, 0.90+/-0.01; FR-trial, 0.86+/-0.03; P<0.01). Blood glucose concentrations were similar in both trials, while blood lactate concentrations were higher in the NF-trial at the end of exercise (4.83+/-0.34 vs 4.18+/-0.38 mM; P<0.05). In summary water ingestion during prolonged running improved endurance capacity. Verf.-Referat