title: Lower injury rates for newcomers to professional soccer: a prospective cohort study over 9 consecutive seasons.
abstract: BACKGROUND
  No study has investigated whether newcomers to professional soccer have a different injury rate than established players.
  
  
  OBJECTIVE
  The primary objective was to investigate whether being a newcomer to professional soccer influences injury rates. The secondary objective was to evaluate whether playing position and player age influence injury rates.
  
  
  METHODS
  Cohort study; Level of evidence, 2.
  
  
  METHODS
  Twenty-six soccer clubs, with 1401 players, were followed prospectively over 9 consecutive seasons between 2001 and 2010. Club medical staff recorded time-loss injuries and soccer exposure on an individual level. Cox regression analyses were used to evaluate associations between time-loss injuries and time in professional soccer, playing position, and age.
  
  
  RESULTS
  In total, 6140 injuries and 797,389 hours of exposure were registered. A decreased general injury rate was observed for newcomers (n = 116) compared with established players (n = 3091) (hazard ratio [HR], 0.77; 95% confidence interval [CI], 0.61-0.99). In contrast, newcomers had a higher rate of fractures (rate ratio [RR], 1.77; 95% CI, 1.05-2.97), especially stress-related bone injuries (RR, 2.68; 95% CI, 1.08-6.69). Using goalkeepers as a reference, all outfield playing positions had significantly higher adjusted injury rates: defenders with an HR of 1.91 (95% CI, 1.64-2.24), midfielders with an HR of 1.78 (95% CI, 1.53-2.07), and forwards with an HR of 1.82 (95% CI, 1.55-2.14). Using players aged ≤21 years as a reference, the overall adjusted injury rate increased with age, with a peak injury rate among players aged 29 to 30 years (HR, 1.44; 95% CI, 1.24-1.68).
  
  
  CONCLUSIONS
  Newcomers to professional soccer had a lower general injury rate than established players but a higher rate of stress-related bone injuries. Being a goalkeeper was associated with lower injury rates than all outfield playing positions. Injury rates increased with age, a pattern that persisted after adjusting for playing position and match exposure.
authors.affiliation: Department of Medical and Health Sciences, Linköping University, SE-581 83 Linköping, Sweden. karolina.kristensson@liu.se
authors.forename: Karolina
authors.initials: K
authors.lastname: Kristenson
authors.forename: Markus
authors.initials: M
authors.lastname: Waldén
authors.forename: Jan
authors.initials: J
authors.lastname: Ekstrand
authors.forename: Martin
authors.initials: M
authors.lastname: Hägglund
mesh_terms: D000328:Adult; D000367:Age Factors; D001265:Athletic Injuries / Q000453:epidemiology*; D016001:Confidence Intervals; D005060:Europe / Q000453:epidemiology; D015775:Fractures, Stress / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012916:Soccer / Q000293:injuries*; D013997:Time Factors; D055815:Young Adult
keywords: age; playing position; risk factor; soccer