title: Higher shoe-surface interaction is associated with doubling of lower extremity injury risk in football codes: a systematic review and meta-analysis.
abstract: BACKGROUND
  Turning or cutting on a planted foot may be an important inciting event for lower limb injury, particularly when shoe-surface traction is high. We systematically reviewed the relationship between shoe-surface interaction and lower-extremity injury in football sports.
  
  
  METHODS
  A systematic literature search of four databases was conducted up to November 2014. Prospective studies investigating the relationship between rotational traction and injury rate were included. Two researchers independently extracted outcome data and assessed the quality of included studies using a modified Downs and Black index. Effect sizes (OR+95% CIs) were calculated using RevMan software. Where possible, data were pooled using the fixed effect model.
  
  
  RESULTS
  Three prospective studies were included (4972 male athletes). The methodological quality was generally good with studies meeting 68-89% of the assessment criteria. All studies categorised athletes into low (lowest mean value 15 nm) or high traction groups (highest mean value 74 nm) based on standardised preseason testing. In all cases, injury reporting was undertaken prospectively over approximately three seasons, with verification from a medical practitioner. Injury data focused on: all lower limb injuries, ankle/knee injuries or ACL injury only. There was a clear relationship between rotational traction and injury and the direction and magnitude of effect sizes were consistent across studies. The pooled data from the three studies (OR=2.73, 95% CI 2.13 to 3.15; χ(2)=3.19, df=2, p=0.21; I(2)=36.5%) suggest that the odds of injury are approximately 2.5 times higher when higher levels of rotational traction are present at the shoe-surface interface.
  
  
  CONCLUSIONS
  Higher levels of rotational traction influence lower limb injury risk in American Football athletes. We conclude that this warrants considerable attention from clinicians and others interested in injury prevention across all football codes.
authors.affiliation: Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Athol
authors.initials: A
authors.lastname: Thomson
authors.affiliation: Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar.
authors.forename: Rod
authors.initials: R
authors.lastname: Whiteley
authors.affiliation: Ulster Sports Academy, University of Ulster, Newtownabbey, County Antrim, UK.
authors.forename: Chris
authors.initials: C
authors.lastname: Bleakley
mesh_terms: D000070598:Anterior Cruciate Ligament Injuries; D001696:Biomechanical Phenomena / Q000502:physiology; D004867:Equipment Design; D005538:Football / Q000293:injuries*; D006801:Humans; D007869:Leg Injuries / Q000209:etiology*; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D012399:Rotation; D012775:Shoes; D012916:Soccer / Q000293:injuries*; D019876:Sports Equipment
keywords: ACL; American football; Football; Injuries; Leg