title: Cross-sectional geometry of weight-bearing tibia in female athletes subjected to different exercise loadings.
abstract: The association of long-term sport-specific exercise loading with cross-sectional geometry of the weight-bearing tibia was evaluated among 204 female athletes representing five different exercise loadings and 50 referents. All exercises involving ground impacts (e.g., endurance running, ball games, jumping) were associated with thicker cortex at the distal and diaphyseal sites of the tibia and also with large diaphyseal cross-section, whereas the high-magnitude (powerlifting) and non-impact (swimming) exercises were not.
  
  
  BACKGROUND
  Bones adapt to the specific loading to which they are habitually subjected. In this cross-sectional study, the association of long-term sport-specific exercise loading with the geometry of the weight-bearing tibia was evaluated among premenopausal female athletes representing 11 different sports.
  
  
  METHODS
  A total of 204 athletes were divided into five exercise loading groups, and the respective peripheral quantitative computed tomographic data were compared to data obtained from 50 physically active, non-athletic referents. Analysis of covariance was used to estimate the between-group differences.
  
  
  RESULTS
  At the distal tibia, the high-impact, odd-impact, and repetitive low-impact exercise loading groups had approximately 30% to 50% (p < 0.05) greater cortical area (CoA) than the referents. At the tibial shaft, these three impact groups had approximately 15% to 20% (p < 0.05) greater total area (ToA) and approximately 15% to 30% (p < 0.05) greater CoA. By contrast, both the high-magnitude and repetitive non-impact groups had similar ToA and CoA values to the reference group at both tibial sites.
  
  
  CONCLUSIONS
  High-impact, odd-impact, and repetitive low-impact exercise loadings were associated with thicker cortex at the distal tibia. At the tibial shaft, impact loading was not only associated with thicker cortex, but also a larger cross-sectional area. High-magnitude exercise loading did not show such associations at either site but was comparable to repetitive non-impact loading and reference data. Collectively, the relevance of high strain rate together with moderate-to-high strain magnitude as major determinants of osteogenic loading of the weight-bearing tibia is implicated.
authors.affiliation: Bone Research Group, UKK Institute for Health Promotion Research, Kaupinpuistonkatu 1, 33501, Tampere, Finland. riku.nikander@uta.fi
authors.forename: R
authors.initials: R
authors.lastname: Nikander
authors.forename: P
authors.initials: P
authors.lastname: Kannus
authors.forename: T
authors.initials: T
authors.lastname: Rantalainen
authors.forename: K
authors.initials: K
authors.lastname: Uusi-Rasi
authors.forename: A
authors.initials: A
authors.lastname: Heinonen
authors.forename: H
authors.initials: H
authors.lastname: Sievänen
mesh_terms: D000293:Adolescent; D000328:Adult; D000886:Anthropometry / Q000379:methods; D015519:Bone Density / Q000502:physiology; D018483:Diaphyses / Q000033:anatomy & histology / Q000502:physiology; D005260:Female; D006801:Humans; D018482:Muscle, Skeletal / Q000502:physiology; D013177:Sports / Q000502:physiology*; D013977:Tibia / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing / Q000502:physiology; D055815:Young Adult