Aerobic power and body size affects the exercise-induced stress hormone responses to varying water temperatures

Eleven active male subjects were used to examine the effects of anthropometrics and aerobic power (VO2max) on the plasma cortisol (CO) and urine excretion of catecholamines (NE and E) and dopamine (D) during exercise in differing water temperatures. Each performed 30 min of cycle ergometer exercise at 60% VO2max while immersed to the neck in 20, 25, 30, and 35 degrees C water (Tw). The change in core temperature (delta Tre) during exercise was related to Tw (p < 0.007). Plasma CO (exercise - rest) increased during the 20 degrees C trials and decreased during the 30 and 35 degrees C trials (p = 0.011). Catecholamines were generally higher during the 20 and 35 degrees C trials than the 25 and 30 degrees C trials, with significance for only D and NE during the 35 degrees C vs. 25 degrees C trials (p < 0.05). Multiple regression analyses (MRA) with CO during the 20 degrees C trials revealed that VO2max and delta Tre were significant partial correlates (p < 0.05), while in 35 degrees C water body mass index and delta Tre were significant partial correlates (p < 0.05). MRAs with NE and E during the 20 degrees C trials indicated that body fat was the only consistent significant partial correlate. The MRA for NE and E during the 35 degrees C trials were not significant; however, the MRA for D was significant. These results indicate that in addition to the core temperature, anthropometrics, and aerobic power affect the exercise-induced stress hormone responses during exposures to cold and warm water.