Background: Intense exercise has been reported as one risk factor for hip and knee osteoarthritis

Physical activity is favorable for peak bone mass but if the skeletal benefits remain and influence fracture risk in old age is debated. In a cross-sectional controlled mixed model design, we compared dual X-ray absorptiometry-derived bone mineral density (BMD) and bone size in 193 active and retired male elite soccer players and 280 controls, with duplicate measurements of the same individual done a mean 5 years apart. To evaluate lifetime fractures, we used a retrospective controlled study design in 397 retired male elite soccer players and 1368 controls. Differences in bone traits were evaluated by Student's t-test and fracture risk assessments by Poisson regression and Cox regression. More than 30 years after retirement from sports, the soccer players had a Z-score for total body BMD of 0.4 (0.1 to 0.6), leg BMD of 0.5 (0.2 to 0.8), and femoral neck area of 0.3 (0.0 to 0.5). The rate ratio for fracture after career end was 0.6 (0.4 to 0.9) and for any fragility fracture 0.4 (0.2 to 0.9). Exercise-associated bone trait benefits are found long term after retirement from sports together with a lower fracture risk. This indicates that physical activity in youth could reduce the burden of fragility fractures.

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A fracture in childhood is associated with low bone mineral density (BMD), but it is debated whether a fracture at growth also predicts low BMD in young adulthood. The purpose of this work was to gender-specifically evaluate whether children with a fracture are at increased risk of low BMD in young adulthood. Distal forearm BMD (g/cm 2 ) was measured with single-photon absorptiometry (SPA) in 47 boys and 26 girls (mean age 10 years, range 3-16 years) with an index fracture and in 41 boys and 43 girls (mean age 10 years, range 4-16 years) with no fracture. BMD was re-measured mean 27 years later with the same SPA apparatus and with dual-energy absorptiometry (DXA), quantitative ultrasound (QUS), and peripheral computed tomography (pQCT). Individual Z-scores were calculated using the control cohort as reference population. Data are presented as means with 95% confidence intervals (95% CI) within brackets and correlation with Pearson's correlation coefficient. Boys with an index fracture had at fracture event a distal forearm BMD Z-score of À0.4 (95% CI, À0.7 to À0.1) and at follow-up À0.4 (95% CI, À0.7 to À0.1). Corresponding values in girls were À0.2 (95% CI, À0.5 to 0.1) and À0.3 (95% CI, À0.7 to 0.1). The deficit in absolute bone mass was driven by men with index fractures in childhood due to low energy rather than moderate or high energy. There were no changes in BMD Z-score during the follow-up period. The BMD deficit at follow-up was in boys with an index fracture verified with all advocated techniques. A childhood fracture in men was associated with low BMD and smaller bone size in young adulthood whereas the deficit in women did not reach statistical significance. ß