title: The preventive effect of the Nordic hamstring exercise on hamstring injuries in amateur soccer players: study protocol for a randomised controlled trial.
abstract: BACKGROUND
  Hamstring injuries are the most common muscle injury in male amateur soccer players and have a high rate of recurrence, often despite extensive treatment and long rehabilitation periods. Eccentric strength and flexibility are recognised as important modifiable risk factors, which have led to the development of eccentric hamstring exercises, such as the Nordic hamstring exercise. As the effectiveness of the Nordic hamstring exercise in reducing hamstring injuries has never been investigated in amateur soccer players, the aim of this study is to investigate the effect of this exercise on the incidence and severity of hamstring injuries in male amateur soccer players. An additional aim is to determine whether flexibility is associated with hamstring injuries.
  
  
  METHODS
  Cluster-randomised controlled trial with soccer teams as the unit of cluster.
  
  
  METHODS
  Dutch male amateur soccer players, aged 18-40 years, were allocated to an intervention or control group. Both study groups continued regular soccer training during 2013, but the intervention group additionally performed the Nordic hamstring exercise (25 sessions over 13 weeks). Primary outcomes are the incidence of initial and recurrent hamstring injury and injury severity. Secondary outcomes are hamstring-and-lower-back flexibility and compliance. Compliance to the intervention protocol was also monitored.
  
  
  CONCLUSIONS
  Eccentric hamstring strength exercises are hypothesised to reduce the incidence of hamstring injury among male amateur soccer players by 70%. The prevention of such injuries will be beneficial to soccer players, clubs, football associations, health insurance companies and society.
  
  
  BACKGROUND
  NTR3664.
authors: Department of Rehabilitation, Nursing Science & Sports, University Medical Center Utrecht, Utrecht, The Netherlands.
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: D000293:Adolescent; D000328:Adult; D006801:Humans; D015994:Incidence; D015601:Injury Severity Score; D007869:Leg Injuries / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D052580:Muscle Stretching Exercises / Q000379:methods*; D018482:Muscle, Skeletal / Q000293:injuries; D009426:Netherlands / Q000453:epidemiology; D010349:Patient Compliance; D055070:Resistance Training / Q000379:methods*; D012916:Soccer / Q000293:injuries*; D013708:Tendon Injuries / Q000453:epidemiology / Q000517:prevention & control*; D055815:Young Adult