Bone health during late adolescence: effects of an 8-month training program on bone geometry in female athletes

This study investigated the short term changes in hip structural parameters in high level adolescent soccers and swimmers.

Twenty-six girl swimmers (15.9±2 years) and 32 girl soccer players (16.2±0.7 years) were investigated before and after 8 months of training. Fifteen non-active age-matched adolescents were enrolled at baseline to serve as a reference group. The geometric contributions to bone strength in the proximal femur were quantified using the hip structural analysis technique.

Eight months of training had increased the bone density in soccer players but not in swimmers. At the total hip, swimmers conserved their baseline low Z-score values while soccers remained above the normal. At the femoral shaft, the cross sectional area had increased for the two groups with a higher magnitude in soccers (3.17% vs 2.31%; P<0.05). The sub-periosteal width had increased in soccer players (P<0.01) but not in swimmers. The Z-score showed an improvement of cross sectional moment of inertia and section modulus at femoral shaft section for soccers (P<0.001), without any change in swimmers. Remarkably, swimmers had improved the Z-score of buckling ratio (P<0.005), while soccers did not.

A season of training for sport characterized by impact had induced significant bone geometry improvement in late adolescent females despite expectations that this period of growth represents a plateau in bone maturation. This study adds to the existing literature describing intensive swimming practice as lacking an osteogenic effect when assessed by dual energy X-ray absorptiometry.