Context: The effect of physical activity on bone mineral density (BMD) is not well investigated longitudinally after puberty in men.
Objective: Our objective was to evaluate the effect of exercise and reduced exercise on BMD after puberty in men.
Design: We conducted a longitudinal study.
Participants: Sixty-three healthy young athletes and 27 male controls, both with a mean age of 17 yr at baseline, participated. Also, 136 of the participants' parents were investigated to evaluate heritable influences.
Main outcome measures: Total body, total hip, femoral neck, and humerus BMD (grams per square centimeter) were measured at baseline and after mean periods of 27, 68, and 94 months in the young cohort.
Results: BMDs of control parents and athlete parents were equal, suggesting absence of selection bias. The 23 athletes that remained active throughout the study increased BMD at all sites when compared with controls (mean difference, 0.04-0.12 g/cm(2); P < 0.05) during the study period. After an average of 3 yr, 27 athletes ended their active careers. Although this group initially lost BMD at the hip compared with active athletes, the former athletes still had higher BMD than controls at the femoral neck (0.12 g/cm(2); P = 0.007), total hip (0.11 g/cm(2); P = 0.02), and humerus (0.10 g/cm(2); P = 0.02) at the final follow-up.
Conclusions: High sensitivity to physical loading persists after puberty in men. Reduced physical activity is associated with BMD loss in the first 3 yr in weight-bearing bone. Sustained benefits in BMD are preserved 5 yr after intensive training ends.