title: Select injury-related variables are affected by stride length and foot strike style during running.
abstract: BACKGROUND
  Some frontal plane and transverse plane variables have been associated with running injury, but it is not known if they differ with foot strike style or as stride length is shortened.
  
  
  OBJECTIVE
  To identify if step width, iliotibial band strain and strain rate, positive and negative free moment, pelvic drop, hip adduction, knee internal rotation, and rearfoot eversion differ between habitual rearfoot and habitual mid-/forefoot strikers when running with both a rearfoot strike (RFS) and a mid-/forefoot strike (FFS) at 3 stride lengths.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  A total of 42 healthy runners (21 habitual rearfoot, 21 habitual mid-/forefoot) ran overground at 3.35 m/s with both a RFS and a FFS at their preferred stride lengths and 5% and 10% shorter.
  
  
  RESULTS
  Variables did not differ between habitual groups. Step width was 1.5 cm narrower for FFS, widening to 0.8 cm as stride length shortened. Iliotibial band strain and strain rate did not differ between foot strikes but decreased as stride length shortened (0.3% and 1.8%/s, respectively). Pelvic drop was reduced 0.7° for FFS compared with RFS, and both pelvic drop and hip adduction decreased as stride length shortened (0.8° and 1.5°, respectively). Peak knee internal rotation was not affected by foot strike or stride length. Peak rearfoot eversion was not different between foot strikes but decreased 0.6° as stride length shortened. Peak positive free moment (normalized to body weight [BW] and height [h]) was not affected by foot strike or stride length. Peak negative free moment was -0.0038 BW·m/h greater for FFS and decreased -0.0004 BW·m/h as stride length shortened.
  
  
  CONCLUSIONS
  The small decreases in most variables as stride length shortened were likely associated with the concomitant wider step width. RFS had slightly greater pelvic drop, while FFS had slightly narrower step width and greater negative free moment.
  
  
  CONCLUSIONS
  Shortening one's stride length may decrease or at least not increase propensity for running injuries based on the variables that we measured. One foot strike style does not appear universally better than the other; rather, different foot strike styles may predispose runners to different types of injuries.
authors.affiliation: Department of Kinesiology, Iowa State University, Ames, Iowa, USA ehageman@iastate.edu.
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Boyer
authors.affiliation: Department of Kinesiology, Iowa State University, Ames, Iowa, USA.
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Derrick
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D005528:Foot / Q000502:physiology*; D005545:Forefoot, Human / Q000502:physiology; D064368:Healthy Volunteers; D006801:Humans; D007719:Knee Joint / Q000502:physiology; D008297:Male; D010388:Pelvis / Q000502:physiology; D012420:Running / Q000293:injuries* / Q000502:physiology; D013312:Stress, Physiological / Q000502:physiology; D055815:Young Adult
keywords: forefoot strike; free moment; iliotibial band; pelvic drop; rearfoot strike; step width