title: Ground reaction forces and bone parameters in females with tibial stress fracture.
abstract: OBJECTIVE
  Tibial stress fracture is a common overuse running injury that results from the interplay of repetitive mechanical loading and bone strength. This research project aimed to determine whether female runners with a history of tibial stress fracture (TSF) differ in ground reaction force (GRF) parameters during running, regional bone density, and tibial bone geometry from those who have never sustained a stress fracture (NSF).
  
  
  METHODS
  Thirty-six female running athletes (13 TSF; 23 NSF) ranging in age from 18 to 44 yr were recruited for this cross-sectional study. The groups were well matched for demographic, training, and menstrual parameters. A force platform measured selected GRF parameters (peak and time to peak for vertical impact and active forces, and horizontal braking and propulsive forces) during overground running at 4.0 m.s.(-1). Lumbar spine, proximal femur, and distal tibial bone mineral density were assessed by dual energy x-ray absorptiometry. Tibial bone geometry (cross-sectional dimensions and areas, and second moments of area) was calculated from a computerized tomography scan at the junction of the middle and distal thirds.
  
  
  RESULTS
  There were no significant differences between the groups for any of the GRF, bone density, or tibial bone geometric parameters (P > 0.05). Both TSF and NSF subjects had bone density levels that were average or above average compared with a young adult reference range. Factor analysis followed by discriminant function analysis did not find any combinations of variables that differentiated between TSF and NSF groups.
  
  
  CONCLUSIONS
  These findings do not support a role for GRF, bone density, or tibial bone geometry in the development of tibial stress fractures, suggesting that other risk factors were more important in this cohort of female runners.
authors.affiliation: Centre for Health, Exercise and Sports Medicine, School of Physiotherapy, The University of Melbourne, Victoria, Australia. k.bennell@unimelb.edu.au
authors.forename: Kim
authors.initials: K
authors.lastname: Bennell
authors.forename: Kay
authors.initials: K
authors.lastname: Crossley
authors.forename: Jyotsna
authors.initials: J
authors.lastname: Jayarajan
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Walton
authors.forename: Stuart
authors.initials: S
authors.lastname: Warden
authors.forename: Z Stephen
authors.initials: ZS
authors.lastname: Kiss
authors.forename: Tim
authors.initials: T
authors.lastname: Wrigley
mesh_terms: D000293:Adolescent; D000328:Adult; D015519:Bone Density; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015999:Multivariate Analysis; D012420:Running / Q000502:physiology*; D013977:Tibia / Q000033:anatomy & histology / Q000502:physiology*; D013978:Tibial Fractures / Q000503:physiopathology*