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.
The purpose of this study was to investigate the differences of the motions between the speed throw and the distance throw, using a three-dimensional(3D) motion analysis. Twenty-four male university baseball players were the subjects of this study. They were asked to throw a ball (mass 0.144kg) horizontally as fast as possible (speed throw: ST), and as far as possible (distance throw: DT). These motions were filmed by two high-speed video cameras. 3D landmark coordinates of the subiects and the ball were calculated by the DLT method. The following kinematic parameters were computed: angle of release, the component velocities of the ball, the 3D angles for the backward/forward lean, right/left lean of the upper torso, and the twist of the torso and those for the abduction/adduction, horizontal flexion/extension, internal/external rotation at the shoulder joint, and the flexion/extension at the elbow joint of the throwing arm. The sequential data were normalized with the time from the stride foot contact to the ball release, and then averaged. Angle of release was significantly larger in the DT than in the ST. Significant difference was not found between the resultant velocity of the ST and the DT. Vertical velocity of the ball was significantly larger in the DT than in the ST during the latter half of the acceleration phase. On the other hand, horizontal velocity of the ball was significantly larger in the ST than in the DT. The backward lean and the left lean angles of the upper torso were also significantly larger in the DT than in the ST throughout the all sequences analyzed. Ranges of these angular displacements between the stride foot contact and the release, however, had no significant difference between the ST and the DT. The shoulder adduction angle was also significantly larger in the DT than in the ST during the latter half of the acceleration phase. These results indicate that the differences in the release parameters between the ST and the DT were caused not only by the throwing arm motions but also by the motions of the upper torso. It has been suggested that the motions to upward and left ward of the upper torso helps to achieve longer throwing distance in the DT, and that forward lean of the upper torso possibly contributes to achieve larger horizontal ball velocity at the release in the ST.
This study investigated the effects of the changes in lower limbs length and body function with age on running ability. The subjects were 133 young boys (2 to 12yrs), 18 male students (18 to 19yrs), and 34 male sprinters (19 to 30yrs). Running abilities were measured by running velocity (RV), step length (SL), and step frequency (SF), respectively. To exclude the effects of lower limb length on running ability, dimensionless numbers; representing index of running velocity (IRV), index of step length (ISL) and index of step frequency (ISF) were calculated. RV and SL of young boys increased linearly with age (2 to 12yrs), but SF showed almost no change. Sprinters demonstrated higher RV and SL than students of similar age. However there were no differences in SF between the two subject groups. Although IRV and ISF increased linearly (r=0.778, p<0.001; r=0.719, p<0.001, respectively) with age (2 to 12yrs), ISL showed no such change (except below 6yrs). The above results indicated that increases in SL with age were caused by both the increasing length of the lower limbs and the improvement in body function (such as neuro-muscular function), and the constant SF with age was maintained by the improvement in body function which counteracts the increase of lower limb mass. Therefore, it was suggested that the development of running velocity with age was resulted from both the increasing length of lower limbs and the improvement in body function.