Water ingestion improves performance compared with mouth rinse in dehydrated subjects

It has been suggested that mouth rinse and/or ingestion of fluids during exercise may have a beneficial effect on performance. However, the existing results are controversial. PURPOSE: We hypothesized that pharyngeal receptor activation through ingestion of a small amount of water could enhance performance better than mouth rinse in dehydrated subjects. METHODS: Ten healthy trained male cyclists (weight = 78.2 ± 2.2 kg, age = 25.9 ± 1.0 yr, body fat = 15.6% ± 1.6%, V̇O _2max = 53.8 ± 4.8 mL•kg ^-1•min ^-1) completed three time-to-exhaustion cycling tests at 75% of their maximum power output after being dehydrated by 2% of their total body weight. Dehydration was induced by a 2-h moderate-intensity exercise (70% of maximum HR), which included 30-min intervals alternating between jogging and cycling in the heat (31°C). All subjects repeated the protocol in random order on three separate occasions: a) mouth rinse with 25 mL of plain water before and every 5 min of the trial (MR), b) ingestion of 25 mL of plain water before and every 5 min (DR), and c) control (CON), where no fluids were provided. Blood and urine samples were collected at the beginning of the dehydration phase, before the performance test, and at the end of the experimental protocol. RESULTS: A significantly greater time to exhaustion was recorded in the DR trial compared with MR and CON trials (21.9 ± 1.2 vs 18.7 ± 1.3 and 17.7 ± 1.1 min, respectively, P < 0.05). There were no differences in mean HR, maximum lactate concentration, or RPE between the three trials (P > 0.05). CONCLUSIONS: The results demonstrated that ingestion of even a small amount of water increased exercise time in dehydrated subjects possibly through activation of pharyngeal receptors.