Previous sport activity during childhood and adolescence is associated with increased cortical bone size in young adult men.

Physical activity during growth has been associated with altered cortical bone geometry, but it remains uncertain if the physical activity-induced increments in cortical bone size remain when the level of physical activity is diminished or ceased. The aim of this study was to investigate if physical activity during growth is associated with cortical bone geometry in currently inactive young men. In this study, 1068 men (18.9 +/- 0.6 [SD] yr) were included. Cortical bone geometry at the tibia and radius were measured using pQCT. A standardized questionnaire was used to collect information about current and previous sport activity. Subjects who continued to be active (n = 678) and who had been previously active (n = 285) in sports had a wider cortical bone (periosteal circumference [PC], 4.5% and 3.2%, respectively) with increased cross-sectional area (CSA; 12.5% and 6.9%) of the tibia than the always inactive subjects (n = 82). In the currently inactive men (n = 367), regression analysis (including covariates age, height, weight, calcium intake, smoking, and duration of inactivity) showed that previous sport activity was independently associated with cortical bone size of the tibia (CSA and PC). Amount of previous sport activity explained 7.3% of the total variation in cortical CSA. Subjects, who ceased their sport activity for up to 6.5 yr previously, still had greater cortical PC and CSA of the tibia than always inactive subjects. The results from this study indicate that sport activity during growth confers positive effects on bone geometry even though sport activity is ceased.