Résumé
<p>The purpose of this study was to examine the age- and athletic event-related differences in trunk muscularity among junior and senior athletes. The cross-sectional areas (CSAs) of the rectus abdominis, lateral abdominal muscle group, psoas major and erector spinae were determined on magnetic resonance imaging for 188 junior athletes aged 12-18 years and 164 senior athletes aged ≥ 19 years in six different athletic events (male: archery, table tennis, Nordic combined, basketball, and wrestling; female: archery, table tennis, and gymnastics). To examine the age-related differences for each athletic event and sex, the subjects were classified into the following age groups: 12-15 years, 16-18 years and senior (≥ 19 years). The main results were as follows. 1) The magnitude relationships of trunk muscle CSA/height<sup>2</sup> differed among the age groups by athletic event and muscle. 2) The values of CSA/height<sup>2</sup> of the lateral abdominal muscle group and erector spinae were significantly larger in female gymnasts aged 12-15 years than in female athletes from the other athletic events. These results respectively indicated that 1) each trunk muscle has the potential to specifically develop according to the athletic events and 2) selective hypertrophy of the trunk muscles can be induced by training reflecting athletic event-specific characteristics in female junior high school athletes.</p>
Résumé
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.
Résumé
The explosive power output of both legs during extension movement was assessed in 271 male (aged 16-84 yr) and 248 female (aged 16-82 yr) subjects, and the table of evaluation for the value obtained was prepared with the function of sex and age. From a sitting position on a seat, leg extension movement was performed toward the foot plate in the forward, to which the body mass of each subject was applied as a resistance. The reliability of the power measurement was ascertained from the result that the coefficients of variation were under 5 x 10<SUP>-2</SUP> when the power output of 6 subjects was measured once a day for 10 days. On both sexes, the power output per body mass declined linearly with age. The regression equations between age (x) and the power output per body mass (y) were as follows.<BR>male: y=-0.22 x+28.38 (r=.659, n=271; p<0.001)<BR>female: y=-0.13 x+18.36 (r=.583, n=248; p<0.001)<BR>For all groups classified by 10 years, the male indicated greater value than the female in corresponding groups. The ratio of the value for the female relative to that for the male was between 64.8% and 72, 0%. These results suggested that the power output for the male decreased at a higher rate, and the sex difference of it decreased as the age increased.
Résumé
Resting O<SUB>2</SUB> consumption following exercise at ventilatory threshold (VT) intensity was measured in order to investigate the magnitude and duration of excess post-exercise O<SUB>2</SUB> consumption in untrained men. Nine untrained males (mean age 24.8±1.5 years) exercised for one hour at VT intensity (58.2±1.7% of VO<SUB>2</SUB>max) on a cycle ergometer, and then rested for 12 h sitting in a comfortable armchair (post-exercise) . On a separate day the subjects rested for 12 h but without preceding exercise (non-exercise) . O<SUB>2</SUB> uptake (VO<SUB>2</SUB>) and heart rate (HR) were measured for 5 min every 30 min throughout the 12 h rest period and again at 24 h following the exercise. High-carbohydrate meals (carbohydrate 112.8±5.1 g, protein 9.7±0.4 g, fat 1.8±0.1 g) were given to the subjects at 2, 7 and 12 h following the exercise. The total energy intake per day was 1591.7±71.8 kcal. V0<SUB>2</SUB> and HR were significantly higher, and respiratory quotient (RQ) was significantly lower at most of the measured time-points for post-exercise than for non-exercise. Total energy consumption for the 12 h rest period was 957.3±25.5 kcal for post-exercise and 840.3±15.8 kcal for non-exercise, respectively. After 24 h no difference was observed in VO<SUB>2</SUB> and HR between post-exercise and non-exercise, but RQ was significantly lower in the former than in the latter (0.86±0.05 vs. 0.90±0.04, p<0.05) . These results suggest that exercise for one hour at VT intensity enhances resting VO<SUB>2</SUB> for at least 12 h, and elevates the rate of fat utilization for at least 24 h.