Low levels of hypohydration and endurance capacity during heavy exercise in untrained individuals

Untrained subjects (n=6n=6) performed three cycle exercise trials at 80% maximal O2 uptake until exhaustion in a climatic chamber (32 °C, 60% relative humidity) under the following three conditions: (1) 2% hypohydration, (2) 1% hypohydration, and (3) euhydration. Exercise tolerance time averaged 7.7±1.5, 14.0±2.4, and 20.9±3.7 min, respectively, under these three conditions. Endurance capacity in untrained individuals is substantially impaired even at low levels of hypohydration during heavy exercise in a compensable hot environment, and this impairment is associated with hypohydration-induced higher initial body temperatures that leads to earlier attainment of a critical core temperature.