Changes in the physiological strain and graded exercise performance due to warming or cooling of the lower body in a temperate environment.

BACKGROUND The effects of a reduced or mildly elevated exercising muscle temperature on the graded exercise test (GXT) performance have yet to be studied. The present study clarified the effects of a range of exercising muscle temperatures on GXT performance in a temperate environment. METHODS Eight male subjects (age, 24.0±0.5 years old; height, 175±2 cm; weight, 64.8±2.0 kg; peak oxygen consumption [V O2peak], 51.1±2.4 ml/kg/min) performed 4 GXTs at different exercising muscle temperatures using a cycle-ergometer in a temperate environment (24.1 ± 0.2 °C). The exercise began at 0.3 kp with 60 rpm and increased 0.3 kp every minute until volitional exhaustion. Subjects passively cooled (averaged deep thigh and calf temperature [Tmm], COLD, 31 °C or COOL, 33 °C) or warmed (Tmm; WARM, 35 °C or HOT, 37 °C) the exercising muscle using water perfusion pants throughout the test. The peak oxygen consumption (V O2peak), exercise time to exhaustion (TTE), heart rate (HR), tympanic (Tty) and mean body temperature (Tb), and total sweat loss were also measured. RESULTS No significant differences were observed in the V O2peak or TTE among the 4 conditions; however, the HR, Tb, and total sweat loss were significantly higher (p<0.05) under warming conditions than cooling conditions. CONCLUSIONS These results suggest that although the cardiovascular and thermoregulatory strain is higher under warming conditions than cooling conditions, the exercising muscle temperature does not affect the performance of a GXT lasting approximately 15 min in a temperate environment.