Abstract
Purpose
Alpine skiing is associated with large skeletal loads with distinct patterns of loading rate and direction, and alpine skiers were previously found to have a robust bone structure compared to normally active controls. However, it is not known whether the mechanical stimuli experienced by skiers are also associated with enhanced bone microarchitecture and strength. Thus, the purpose of this study was to use high-resolution peripheral quantitative computed tomography (HR-pQCT) to compare bone macro- and microarchitecture and bone strength between elite alpine skiers and normally active controls.
Method
Participants included 7 female and 12 male members of the Canadian Alpine Ski Team, and 10 female and 16 male normally active control subjects. A whole body dual energy X-ray absorptiometry (DXA) scan was performed to measure lean mass and percent body fat. HR-pQCT (XtremeCT, Scanco) was used to assess bone macro- and microarchitecture including total, cortical and trabecular bone area, total and cortical bone mineral density (BMD), and bone volume ratio (BV/TV) of the dominant distal tibia and radius. Finite element analysis was applied to the HR-pQCT scans to estimate bone strength (failure load, N). Analysis of covariance (ANCOVA) was used to compare outcomes between groups adjusting for body weight (tibia) and height (tibia and radius).
Results
Bone area of the distal radius was significantly greater in female (30%, p<.001) and male (21%, p=.003) skiers compared with controls. Similarly, distal radius failure load was greater in female (37%, p=.001) and male (42%, p<.001) skiers. Higher BV/TV was apparent in the distal tibia of the male (18%, p=.005) and female skiers (19%, p=.012) and at the radius for the male skiers (19%, p=.02) compared with controls. High BV/TV is associated with a higher trabecular area at the distal tibia for the female athletes (14%, p=.06) and the distal radius for male athletes (32%, p=.002). Distal tibia failure load was higher in male (18%, p<.001) and female skiers (22%, p=.012) compared with controls. Distal tibia failure load remained significantly higher for the male athletes even after adjusting for lean mass.
Conclusion
Compared to controls, skiers have larger bone areas at the radius in men and women, and at the tibia in women. Trabecular bone volume is augmented in skiers compared with controls, even after adjusting for height and weight. After adjusting for lean mass, group differences in bone strength were still apparent at the distal tibia in men, suggesting that direct mechanical input associated with alpine skiing affects bone microarchitecture. In conclusion a larger bone size and greater trabecular bone volume may represent skeletal adaptations to the extreme mechanical environment experienced during competitive skiing, and likely contribute to the greater bone strength observed in skiers compared with controls at both skeletal sites.
