title: Can the natural turf pitch be viewed as a risk factor for injury within Association Football?
abstract: OBJECTIVE
  A review of the current literature is used to propose a 'conceptual model for relative pitch hardness' and how this may affect incidence of injury within Association Football. Based upon the injury risk and causation model of Meeuwisse et al. (Clin J Sport Med 2007; 17(3):215), it may provide researchers a necessary framework to guide future research investigations.
  
  
  METHODS
  A literature review.
  
  
  METHODS
  A comprehensive search of electronic databases available until October 2014, and supplemental hand searching was conducted to identify relevant studies. Studies were deemed relevant if they met the following criteria: published in English, presented or referenced in an epidemiological study or provided data directly and/or related to the surface of the football pitch, ball or boot to surface interaction and injury. Further information was sourced on surface hardness, players' movement patterns and physiological demands within football.
  
  
  RESULTS
  Papers varied in methodological quality, with comparative studies examining injury rates on artificial versus natural turf pitches being most prevalent. No prospective studies were found that objectively measured the relationship between hardness of natural turf and injury risk within football.
  
  
  CONCLUSIONS
  The literature review into natural turf pitches and injury within football has largely been unable to confirm that pitch hardness can be viewed as a significant extrinsic risk factor. Methodological concerns, including objectivity in pitch assessment and uniformity in defining injuries undermine the efficacy of available work. Future studies are needed utilising objective assessment tools to draw more definitive conclusions regarding pitch hardness as an extrinsic factor for injury within football.
authors.affiliation: Leicester City Football Club, Department of Medicine and Sports Science, King Power Stadium, England. Electronic address: dave.rennie@lcfc.co.uk.
authors.forename: David J
authors.initials: DJ
authors.lastname: Rennie
authors.affiliation: Biomechanics, Liverpool John Moores University, England.
authors.forename: Jos
authors.initials: J
authors.lastname: Vanrenterghem
authors.affiliation: Sport Social Science, Liverpool John Moores University, England.
authors.forename: Martin
authors.initials: M
authors.lastname: Littlewood
authors.affiliation: Applied Physiology, Liverpool John Moores University, England.
authors.forename: Barry
authors.initials: B
authors.lastname: Drust
mesh_terms: D001265:Athletic Injuries / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D006109:Poaceae; D012307:Risk Factors; D012916:Soccer / Q000293:injuries* / Q000502:physiology*
keywords: Hardness; Injuries; Natural turf; Soccer/football; Sports surfaces