title: Muscle injury rates in professional football increase with fixture congestion: an 11-year follow-up of the UEFA Champions League injury study.
abstract: BACKGROUND
  The influence of fixture congestion on injury rates and team performance has only been scarcely investigated.
  
  
  OBJECTIVE
  To study associations between recovery time and match load and injury rates and team performance in professional football.
  
  
  METHODS
  Exposure and time loss injuries were registered prospectively from 27 teams over 11 seasons. Matches were grouped according to recovery days before each match (≤3 vs >3 days, and ≤4 vs ≥6 days). Injury rates and team performance were compared between groups. Match load in match sequences containing five consecutive matches was determined by the number of days separating the first match and the last training session during that match sequence. Linear regression was used to study associations between match load and injury rates and team performance.
  
  
  RESULTS
  Team performance showed no association with match load, or recovery days prior to matches, except for Europa League matches that indicated more matches lost with short recovery (≤3 days) (p=0.048). Total injury rates and muscle injury rates were increased in league matches with ≤4 days compared with ≥6 days' recovery (RR 1.09, 95% CI 1.00 to 1.18, and RR 1.32, 95% CI 1.15 to 1.51, respectively), specifically hamstring and quadriceps injuries. High match load was associated with increase in muscle injury rate in matches in the same match sequence (p=0.012), and increase in ligament injury rate in training in the subsequent match sequence (p=0.003).
  
  
  CONCLUSIONS
  Fixture congestion was associated with increased muscle injury rates but had no, or very limited, influence on team performance.
authors.affiliation: Football Research Group, Linköping University, Linköping, Sweden. hakbe194@student.liu.se
authors.forename: Håkan
authors.initials: H
authors.lastname: Bengtsson
authors.forename: Jan
authors.initials: J
authors.lastname: Ekstrand
authors.forename: Martin
authors.initials: M
authors.lastname: Hägglund
mesh_terms: D001265:Athletic Injuries / Q000453:epidemiology / Q000503:physiopathology; D054874:Athletic Performance / Q000502:physiology; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries* / Q000502:physiology; D011446:Prospective Studies; D020127:Recovery of Function; D012307:Risk Factors; D012916:Soccer / Q000293:injuries* / Q000502:physiology; D013997:Time Factors; D016526:Workload / Q000706:statistics & numerical data
keywords: Fatigue; Muscle damage/injuries; Soccer; Sporting injuries