title: Hip Musculoskeletal Conditions and Associated Factors That Influence Squat Performance: A Systematic Review.
abstract: BACKGROUND
  The squat is a fundamental movement for weightlifting and sports performance. Both unilateral and bilateral squats are also used to assess transitional and dynamic lower-extremity control. Common lower-extremity conditions can have an influence on squat performance. Of interest are the effects of hip musculoskeletal conditions and associated factors, such as hip muscle pain, fatigue, and tightness, on squat performance. Currently, there has been no appraisal of the evidence regarding the association of these conditions and associated factors on squat performance.
  
  
  OBJECTIVE
  This study evaluated the current evidence regarding common hip musculoskeletal conditions and associated factors, such as hip muscle pain, fatigue, and tightness, on squat performance.
  
  
  METHODS
  A systematic review was conducted according to preferred reporting items for systematic reviews and meta-analyses guidelines. A search of PubMed, CINAHL, SPORTDiscus, ProQuest, and Google Scholar® was conducted in October, 2016 using the following keywords alone and in combination: hip, joint, arthritis, pain, range of motion (ROM), fatigue, tightness, pathology, condition, muscle, intraarticular, extraarticular, femoroacetabular impingement, single leg, bilateral, squat, performance, and technique. The grading of studies was conducted using the Physiotherapy Evidence Database scale.
  
  
  RESULTS
  The authors identified 35 citations, 15 of which met the inclusion criteria. The qualifying studies yielded a total of 542 subjects (160 men and 382 women; mean age = 29.3 (5.9) y) and measured performance with either the barbell squat, step down, bilateral, or single-leg squat. Femoroacetabular impingement and hip arthroscopy were the only hip conditions found that affected the squat. Associated factors, such as muscle pain, fatigue, and tightness, also influenced squat performance.
  
  
  CONCLUSIONS
  This review found that common hip conditions and associated factors and their effects on squat performance to be underinvestigated. Future research should focus on the association between common hip conditions and squat performance.
authors.forename: Scott W
authors.initials: SW
authors.lastname: Cheatham
authors.forename: Kyle R
authors.initials: KR
authors.lastname: Stull
authors.forename: Mike
authors.initials: M
authors.lastname: Fantigrassi
authors.forename: Ian
authors.initials: I
authors.lastname: Montel
mesh_terms: D001182:Arthroscopy; D054874:Athletic Performance; D001696:Biomechanical Phenomena; D057925:Femoracetabular Impingement / Q000503:physiopathology; D006615:Hip / Q000502:physiology*; D006801:Humans; D018763:Muscle Fatigue; D018482:Muscle, Skeletal / Q000502:physiology*; D063806:Myalgia / Q000503:physiopathology; D016059:Range of Motion, Articular
keywords: arthritis; femoroacetabular; joint; pain; technique