The changes of left and right leg movement on curved path during the latter half of 400m sprint / 体力科学

The purpose of this study was to clarify the changes of left and right leg movement on curved path during the latter half of 400m sprint. Subjects were 8 male university sprinters (age 20.0 ± 1.2, height 1.75 ± 0.07m, weight 64.7 ± 6.2kg, personal best for 400m 50.98 ± 2.36sec). The subjects performed 400m sprint with maximal effort on the 1st lane in outdoor track. Trials were recorded and analyzed by two-dimensional motion analysis method focusing on 160-360m section during 400m sprint. This section was divided into five 40m phases (In straight , Beginning of curve, Center of curve, End of curve, and Out straight). The kinematics parameters were averaged for each phase and compared between the phases and between the left and right legs. The running velocity and the step frequency decreased significantly after the Center of curve in both legs. The stance time and the flight time increased significantly after the Center of curve in left leg and the right leg, respectively. Although, the step length of the left leg decreased significantly after the End of curve, the right leg showed no significant difference. Also, the stance distance of the left leg decreased significantly after the End of curve. Form these results, the present study demonstrated that the changes of movement and the factors affecting the decline in running velocity are different between left and right legs on curved path during the latter half of 400m sprint.

AGE- AND BENDER RELATED DIFFERENCES IN KNEE EXTENSION TORQUE AND LAG EXTENSION POWER / 体力科学

This study was aimed to investigate the influences of age and gender on isometric muscle torque and explosive muscle power output with reference to muscle volume. A total of 177 healthy subjects of both genders were divided into four groups according to their age and gender : 46 young men (22.0±3.2yrs), 43 young women (22.7±3.3yrs), 46 elderly men (71.2±4.3yrs) and 42 elderly women (72.7±4.5 yrs) . The maximal voluntary isometric knee extension torque of the right leg (hip and knee angle at 90 degrees) and the power of bilateral leg extension in sitting position were mea sured. The ratios of both torque and power to muscle volume, estimated using ultrasonograph measurement, was calculated (torque/MV and power/MV respectively) . Torque was significantly less among the elderly than among the young for both genders, and among women than among the men for both age groups. Significant age-related differences were evident even in terms of torque/ MV, but the corresponding differences between men and women disappeared. On the other hand, power MV showed significant age- and gender-related differences, and the age-related difference was larger than that for torque MV. These results suggest that age- and gender-related differences in power are more noticeable than differences in torque and that these differences are not simply explained by differences in muscle volume.