The aim of this study was to investigate the developmental characteristics of change of direction ability in junior and youth male soccer players from 13-18 age, and to determine the influence of the basic abilities that constitute change of direction running in each age groups. Change of direction running was measured by laser measuring instrument system. First, based on the 0 m position, participant started to run from -10 m position, turned the change of direction at cutting line (5 m passed from 0 m position) and ran back to the 0 m position again. The results showed that the change of direction running time for 15-16 and 17-18 groups was significantly faster than 13-14 groups, but that the difference was other than cutting phase. Furthermore, the basic abilities that comprise change of direction running were found to differ with age. That is, sprint ability had a strong influence on change of direction running for 13-14 groups ; however, as players grew older, cutting ability also came to have a strong influence in addition to sprint ability.
The purpose of this study was to identify the typical motor patterns of Basic Vaulting-Box movement (straddle-vault) for elementary school children based on observational evaluation, and to discuss the teaching points according to their proficiency levels. The subjects were 453 children (220 boys, 233 girls) from the 3rd-6th grade. They performed a straddle-vault and then motions were recorded from the left and front side. The motions were scored by the evaluation criterion made from descriptions in prior researches and movements of elementary school children and university students. Latent Class Analysis (LCA) was used to extract characteristic motions based on the response patterns to the criterion.
The results were summarized as follows:
1 ．The observational evaluation criterion of straddle-vault comprised 30 items was created from consideration of the motion causality.
2 ．Children's straddle-vault motions were categorized into five patterns: Failure vaulting, Arm dependent vaulting, Landing unstable vaulting, Stable vaulting and Strong push-off vaulting.
3 ．From the viewpoint of success or failure of the vault, achievement rate rises as the grade increases.
4 ．From the viewpoint of performance of the technique, it can not be said that high proficiency movements will increase with progress of grade.
【Purpose】This study aimed to investigate the relationship between structural properties (length and cross-sectional area of the Achilles tendon) and the age of peak height velocity (PHV) and to examine if imbalance between the growth of bone and the muscle-tendon unit occurs around PHV.
【Methods】Eighty-seven Japanese children and adolescents aged 6.2 to 17.9 participated in this study. Based on their estimated age at PHV, the participants were separated into 3 groups (before adolescent growth spurt group: BA, initiation of adolescent growth spurt group: IA, and after PHV group: AP). The Achilles tendon length was defined as the distance between the distal myotendinous junction of the medial gastrocnemius and the Achilles tendon insertion at the calcaneus. Both the length and cross-sectional area of the Achilles tendon were measured by using an ultrasonography technique. Relative Achilles tendon length and relative Achilles tendon cross-sectional area were calculated as a ratio of lower-leg-length (the distance between the popliteal crease and the malleolus lateralis) to the Achilles tendon length and as a ratio of body mass to the Achilles tendon cross-sectional area, respectively.
【Results】The length and cross-sectional area in IA and AP were significantly greater than those of BA. However, no group differences were observed in the relative Achilles among the groups (BA: 51±5％, IA: 52±4％, AP: 49±4％), and the relative cross-sectional area was significantly greater in BA than that of the other groups (BA: 2.2±0.2 kg/mm2, IA: 1.9±0.1 kg/mm2, AP: 1.3±0.1 kg/mm2).
【Conclusion】These results indicate that the imbalance of growth between bone length and muscletendon unit is not observed, and the proportion of tendon length to bone length is constant from childhood to adolescence. In addition, the children and adolescents before the adolescent growth spurt may protect tendon injuries because of the relatively larger tendon cross-sectional area.