The purpose of the present investigation was to examine the relationships between the exercise history and the bone mineral density (BMD) and bone mineral content (BMC) in female Japanese young adults using dual X-ray absorptiometry (DXA). One-hundred twenty females, aged between 18 to 28 years, participated in the present investigation. The BMD at the lumbar spine (L-BMD), whole body BMD and BMC (WB-BMD and WB-BMC), lean body mass (LBM) and fat mass (FM) were measured by DXA. Using a self-administrered questionnaire, the exercise habits during preschool (4-6 years), primary school (7-12 years), junior high school (13-15 years), high school (16-18 years), and the current habits (>18 years) were eveluated. The L-BMD, WB-BMD and WB-BMC were significantly higher in the subjects with exercise habits during both the period of <18 years and >18 years compared with those in the subjects without an exercise history during all periods (p<0.05). In a separate analysis with the data stratified by the school age, the subjects with an exercise history during primary school, junior high school, or high school had significantly higher BMD and BMC values compared with the non-exercisers (each, p<0.05). In contrast, the BMD and BMC did not differ significantly according to either the exercise history during pre-school nor the current exercise status. A multiple stepwise regression analysis revealed that the body weight, LBM, FM, age of menarche, and exercise habits during high school were significant determinants of the L-BMD, WB-BMD and WB-BMC (p<0.001). The results of the present investigation show that both the exercise history during school age and the current exercise habits affect the BMD and BMC in young adults. In particular, high school females should be encouraged to participate in the regular exercise to increase their bone health. Future studies will be needed to confirm the targeted age-group(s) for participation in sports/exercise for the improvement of bone health, including an analysis of the type and intensity of exercise/sports.
