Lower birth weight has been associated with lower cardiorespiratory fitness（CRF）and muscular strength in later life. The aim of this study was to examine whether physical activity may modify associations of birth weight with CRF and muscular strength in children, as well as the relative contributions of birth weight and current physical activity levels to the fitness. The subjects were 535 elementary school children aged 7-12 years. Data were collected on current weight and height. Birth weight was reported according to the Maternal and Child Health Handbook records. CRF was measured by a 20 metre shuttle run test and muscular strength was assessed by grip strength. Information on physical activity was obtained by a questionnaire filled by parents, which asks weekly time spent on habitual exercise activity（min/week).We calculated the time spent in exercise activity higher than 3 METs as moderate to vigorous physical activity（MVPA）and higher than 6 METs as vigorous physical activity（VPA). Lower birth weight was associated with lower CRF（β = 0.087, p = 0.010), after adjustment for sex, months of age, schools, and current height and body mass index（kg/m²). This association was little changed by MVPA（β = 0.090, p＝0.008）or VPA（β = 0.088, p = 0.007), however, VPA was a stronger predictor of CRF than birth weight（β = 0.237, p ‹ 0.001). Birth weight was not associated with muscular strength. The results showed that the association of birth weight with CRF was not modified by physical activity levels in childhood. However, VPA was found to be a stronger predictor of CRF than was birth weight, suggesting that physically active lifestyle which focus on vigorous intensity activity may have a much more important role in development of CRF than an individualʼs low birth weight.

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The purpose of present study was to investigate developmental process of a dodgeball throwing motion in elementary school children. The subjects were 239 elementary school children (114 boys and 125 girls) ranging grade from first to sixth. They were videotaped during a dodgeball throwing motions. One teacher specializing in health and physical education, five third- and fourth-year students of the Department of Education, and four graduate students observed the childrenʼs throwing motions and classified them. In the classification, the observers were not informed of the results (distances) of dodgeball throws. The results of analysis revealed that eight typical throwing patterns were observed in elementary school children, and that the throwing pattern developed along with grade from the immature pattern to more mature patterns progressively. Both boys and girls a dodgeball throwing distance developed with grade. In terms of their throwing motions, girls were inferior to boys ; a larger number of girls : stepped forward with their right (left) leg when they threw the ball using the right (left) hand ; did not take a step or twist the trunk at the moment of throwing the ball；threw the ball underhanded. There were sex differences in both the distance of throws and throwing motion.

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This study aimed to clarify the effects of physical activity on the body type, physical fitness and motor ability in elementary school students living in Aomori prefecture. Subjects were 448 elementary school students (226 boys, 222 girls) living in Aomori Prefecture. As morphometry, we measured height and weight, and calculated the obesity index as an indicator of body type. Physical fitness and motor ability tests were grip strength, 20 m dash, side steps, standing long jump and the speed of the tennis ball throw. Physical activity was evaluated by pedometer, worn around the waist for 7 days. We examined the relationship between physical activity and body type. As a result, there was no significant correlation between physical activity and obesity index. In order to remove the influence of development of physical fitness and motor ability, T score of physical fitness and motor ability were calculated based on the age at the time of measurement by polynomial. Correlation analysis between physical activity and T score of physical fitness and motor ability showed a positive correlation between physical activity on weekdays and standing long jump in boys. A positive correlation was shown for the relationship between physical activity in weekdays and side steps and tennis ball-throwing velocity, physical activity in weekends and 20 m dash, side steps and tennis ball-throwing velocity, respectively, in girls. These results suggest that physical activity does not influence on body type in elementary school students who live in cold district. In addition, it is shown a weak correlation between physical activity and physical fitness and motor ability.

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