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

OBJECTIVES: This study investigated the short term changes in hip structural parameters in high level adolescent soccers and swimmers.
METHODS: 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.
RESULTS: 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. DISCUSSION/
CONCLUSION: 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.