The purpose of this study was to clarify the relationship between the physique and bone strength of tibia in 19 junior high school male soccer players. The bone strength was measured by the speed of sound of the tibia (t-SOS, m/sec) using a SoundScan 2000 Compact (Myriad Ultrasound System Ltd., Israel). We enrolled 45 junior high school boys who did not exercise other than physical education classes as a control group. There were no significant differences between the soccer players and the control group in the height, body weight and calcium intake from dairy products. The length of tibia in the soccer players (40.5±1.9 cm) was significantly longer than in the control group (38.4±2.2 cm) (p < 0.05). The length of tibia / height in the soccer players (24.8±0.9 %) was significantly higher than in the control group (23.9±1.1 %) (p < 0.05). t-SOS in the soccer players (3720±71 m/sec) was significantly lower than in the control group (3778±113 m/sec) (p < 0.05). The value of t-SOS demonstrated a positive correlation with calcium intake from dairy products in the soccer players (r = 0.63 p < 0.05).

These results suggest the possibility that the lower t-SOS values in the junior high school soccer players were affected by the longer length of tibia. Therefore, instruction for soccer players should reflect an understanding of these physical features. It is speculated that the effects of calcium intake on bone formation are greater in the soccer players than in the non-players. The optimal amount of calcium to be taken should be determined according to individual amount of physical activity.