Abstract
The athletic ability and morphological features of judo practitioners at different stages of growth need to be understood in relation to an individual’s biological maturity. Large, powerful atheletes have an advantage, especially in judo training. Bone age is a reliable indicator of biological maturity, and to discover and foster potentially talented judo practitioners, it is important to obtain measurements of bone age. Conventional approaches to bone age assessment have required X-rays, making it difficult to carry out bone age measurements on all candidates. To eliminate the need for X-rays, an ultrasonic bone age measuring device has recently been developed. In this study, we measured morphological features and physical fitness levels of young judo practitioners, and also measured bone age using this new ultrasonic device. The subjects were a group of 48 elementary school-age judo practitioners belonging to the “F Judo Club,” which is a training and fostering project supported by the Fukuoka Judo Federation. According to the Rohrer index, almost half of the practitioners were “rather fat,” demonstrating a trend toward obesity. The Rohrer index is more strongly correlated with percentage of body fat than with body weight, indicating a potentially effective measure for monitoring physical characteristics. Almost all the subjects were advanced in bone age relative to chronological age, showing that they tended to be early maturers. No difference in bone age was observed between the strong practitioners who were selected by the Fukuoka Judo Federation and others. In a subgroup of female subjects, bone age was correlated with back strength and vertical jump height ability. We conclude that bone age measurement, which allows a better understanding of the individual capabilities and physical characteristics of elementary school-age practitioners, would be very useful for the planning of training based on individual levels of development and growth.
