The purpose of this study was to investigate relationships between the velocity of the center of gravity (CGV) and the ground reaction force in side step and cross step cutting. The subjects were five university students belonging to the American football club. In the experimental trials, subjects changed their running direction by 45, 90 and 135 degrees in both side step and cross step. These were videotaped at 60 fields/s with two VTR cameras and the ground reaction force data of the support leg were measured using a force platform. Twenty-five body landmarks were digitized and their three- dimensional coordinate data were reconstructed using the DLT method. The horizontal component of the ground reaction force was divided into two directions: parallel, and normal to CGV. There was positive correlation between the angle of direction change of CGV and the impulse normal to CGV. The angle of changing direction of CGV in the second half of the support was larger, and CGV at mid-support was smaller in side step than cross step. However, there was no significant difference in the impulse normal to CGV in the second half of the support between side and cross step. These results suggested that although the ground reaction forces normal to CGV changed the direction of CGV, the amount of direction change of CGV was affected not only by the magnitude of the ground reaction force acting normal to CGV direction but also by the magnitude of CGV.

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The purpose of this study was to clarify the effectiveness of insoles on improving body stabilization while standing. Thirty three healthy subjects, 17 males (mean age 20.8 ± 1.4 yrs) and 16 females (mean age 21.7 ± 1.7 yrs) were participated voluntarily in this study. The planter pressure distribution and center of pressure (COP) were measured. Then the insoles were assigned with the position of COP in foot. The postural sway during 30 seconds was measured with two force plates and tested on 4 conditions; 1) putting on nothing with eye opened, 2) putting on insoles with eyes opened, 3) putting on nothing with eyes closed, 4) putting on insoles with eyes closed. Parameters examined in this study were the environmental area, the rectangular area, the total shifting length, the root mean of square area, the path length, and the area mean path length as calculated by a postural sway-analyzing system. The averaged position of COP was in backward and leftward. The tendency that the postural sway putting on insoles was lower than putting on nothing was seen. Especially under the condition of the eye closed, the Value on the insoles showed significantly lower than the value on nothing (p＜0.05). According to being intercepted the visual information by eyes closed, sensory input of the sole could be increased and postural sway was decreased. These results suggest that the insoles decrease postural sway and an effect on the stability while standing under the condition of the eye closed.

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The purpose of this study was to examine the influence of the combined endurance and strength training (EST) following the strength or endurance training on maximum strength and aerobic power development in women. Ten women were divided into two groups: the 12wk of EST after 12wk of endurance training alone (ES, n=5) or the 12wk of EST after 12wk of strength training alone (SE, n=5). Assessment of body composition, one-repetition maximum (1RM) of bench press and squat, and maximal oxygen uptake (VO2max) were determined before training, and after 12wk and 24wk of training. Body weight and percent body fat were significantly decreased in the ES and SE groups after 24wk of training. After 24wk of training, VO2max significantly improved, but did not significantly differ between ES and SE group. Maximum strength (1RM of bench press and squat) increased similarly in both group, while 1RM of squat in ES group was significantly lower than that in SE group. These data indicate that EST after endurance training in women does not interfere with VO2max and upper body strength development, but may attenuate a development of lower body strength.

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