1995 Volume 40 Issue 2 Pages 80-88
This study examined the hormonal and metabolic responses during low intensity prolonged swimming at different water temperatures. Six male swimmers swam for 120min at a speed of 0.4m/sec in a swimming flume, at water temperature of 23℃, 28℃ and 33℃. Oxygen uptake (VO_2) and blood samples were collected at rest and every 30min during swimming. Also body temperature was recorded continuously during swimming. VO_2 was higher in the 23℃ (1,814±82ml/min, 50±2%VO_<2max>) trial than in the 28℃ (1,558±117ml/min, 43±2%VO_<2max> : p<0.05) and 33℃ (1,519±81ml/min, 42±2%VO_<2max>: P<0.01) trials. Rectal temperature (Tr) decreased during swimming in 23℃ and 28℃(p<0.05), but not in 33℃. Although there were no differences between Tr in 23℃ and 28℃ trials, mean skin temperature was lower in the 23℃ trial (p<0.01). In all trials plasma catecholamines, free fatty acid and glycerol concentrations increased continuously with exercise duration, whereas insulin decreased. However, cortisol, glucose and glucagon concentrations did not change during swimming. Growth hormone (GH) concentration at the end of the 23℃ and 28℃ trials was higher than in the 33℃ trial. No differences were found in hormonal and metabolic responses except in GH between the 28℃ and 33℃ trials. In 23℃ trial, plasma noradrenaline, dopamine, lactate and free fatty acid concentrations were higher than those in the 28℃ and 33℃ trials(p<0.05-p<0.01). In conclusion, cold water prolonged swimming at low intensity may enhance catecholamines, lactate and growth hormone secretion as a direct consequence of cold stress. Furthermore, the present study indicates that there is no effect of water temperature warmer than 28℃ on the hormones measured in this study during low intensity swimming.