Abstract
The purpose of this study was to investigate the relationship between bone mass and lifestyle, physical fitness and body composition in 394 Japanese junior high school students of both genders. We measured transmission index (TI) and speed of sound (SOS) at the calcaneus using an AOS-100 instrument (ALOKA Co., Ltd., Tokyo). Osteo sono-assessment index (OSI) was calculated from the TI and the SOS, and used as an index of bone mass. OSI was found to increase with age, and there was no significant difference in OSI between the genders. Height, weight, BMI and lean body mass had a significant association with OSI in both males and females. There was no significant relationship between OSI and intake of calcium-rich foods. OSI was correlated with indicators of muscle strength (grip strength, standing broad jump, repetitive sideways jump) and endurance. Subjects, both male and female, who habitually exercised showed high OSI values. Female subjects after menarche had higher OSI values than those before menarche. In junior high school students, not only OSI but also height and weight increased. Furthermore height and weight have an effect on OSI. The present findings suggest that OSI is significantly related to habitual exercise and physical fitness. However, there is no significant relationship between OSI and dietary habits.
