title: The preventive effect of the nordic hamstring exercise on hamstring injuries in amateur soccer players: a randomized controlled trial.
abstract: BACKGROUND
  Hamstring injuries are the most common muscle injuries in soccer, and they have a high rate of recurrence. Eccentric hamstrings strength is recognized as an important modifiable risk factor. This led to the development of prevention exercises such as the nordic hamstring exercise (NHE). The effectiveness of the NHE on hamstring injury prevention has never been investigated in amateur soccer.
  
  
  OBJECTIVE
  To investigate the preventive effect of the NHE on the incidence and severity of hamstring injuries in male amateur soccer players.
  
  
  METHODS
  Randomized controlled trial; Level of evidence, 1.
  
  
  METHODS
  Male amateur soccer players (age, mean ± SD, 24.5 ± 3.8 years) from 40 teams were randomly allocated to an intervention (n = 20 teams, 292 players) or control group (n = 20 teams, 287 players). The intervention group was instructed to perform 25 sessions of NHE in a 13-week period. Both the intervention and control groups performed regular soccer training and were followed for hamstring injury incidence and severity during the 2013 calendar year. At baseline, personal characteristics (eg, age, injury history, field position) were gathered from all participants via a questionnaire. Primary outcome was injury incidence. Secondary outcomes were injury severity and compliance with the intervention protocol.
  
  
  RESULTS
  A total of 38 hamstring injuries were recorded, affecting 36 of 579 players (6.2%). The overall injury incidence rate was 0.7 (95% CI, 0.6-0.8) per 1000 player hours, 0.33 (95% CI, 0.25-0.46) in training, and 1.2 (95% CI, 0.82-1.94) in matches. Injury incidence rates were significantly different between the intervention (0.25; 95% CI, 0.19-0.35) and control groups (0.8; 95% CI, 0.61-1.15), χ(2)(1, n = 579) = 7.865; P = .005. The risk for hamstring injuries was reduced in the intervention group compared with the control group (odds ratio, 0.282; 95% CI, 0.110-0.721) and was statistically significant (P = .005). No statistically significant differences were identified between the intervention and control groups regarding injury severity. Compliance with the intervention protocol was 91%.
  
  
  CONCLUSIONS
  Incorporating the NHE protocol in regular amateur training significantly reduces hamstring injury incidence, but it does not reduce hamstring injury severity. Compliance with the intervention was excellent.
authors: Department of Rehabilitation, Nursing Science & Sports, University Medical Center Utrecht, Utrecht, the Netherlands n.vanderhorst-3@umcutrecht.nl.
authors: Nick
authors: N
authors: van der Horst
authors: Department of Rehabilitation, Nursing Science & Sports, University Medical Center Utrecht, Utrecht, the Netherlands.
authors: Dirk-Wouter
authors: DW
authors: Smits
authors: Arthroscopic Center Amager, Copenhagen University Hospital, Hvidovre, Copenhagen, Denmark.
authors: Jesper
authors: J
authors: Petersen
authors: FIFA Medical Center, Royal Netherlands Football Association, Zeist, the Netherlands.
authors: Edwin A
authors: EA
authors: Goedhart
authors: Department of Rehabilitation, Nursing Science & Sports, University Medical Center Utrecht, Utrecht, the Netherlands.
authors: Frank J G
authors: FJ
authors: Backx
mesh_terms: D000328:Adult; D001265:Athletic Injuries / Q000453:epidemiology / Q000517:prevention & control*; D015444:Exercise / Q000502:physiology*; D005081:Exercise Therapy / Q000379:methods; D006801:Humans; D015994:Incidence; D007869:Leg Injuries / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D018482:Muscle, Skeletal / Q000293:injuries; D012306:Risk; D012307:Risk Factors; D012916:Soccer / Q000293:injuries*; D017695:Soft Tissue Injuries / Q000517:prevention & control; D011795:Surveys and Questionnaires; D013848:Thigh / Q000293:injuries; D055815:Young Adult
keywords: eccentric strengthening; hamstring injuries; injury prevention; nordic curl; nordic hamstring exercise; soccer