title: Preventive effect of eccentric training on acute hamstring injuries in men's soccer: a cluster-randomized controlled trial.
abstract: BACKGROUND
  The incidence of acute hamstring injuries is high in several sports, including the different forms of football.
  
  
  OBJECTIVE
  The authors investigated the preventive effect of eccentric strengthening of the hamstring muscles using the Nordic hamstring exercise compared with no additional hamstring exercise on the rate of acute hamstring injuries in male soccer players.
  
  
  METHODS
  Randomized controlled trial; Level of evidence, 1.
  
  
  METHODS
  Fifty Danish male professional and amateur soccer teams (942 players) were allocated to an intervention group (461 players) or a control group (481 players). Players in the intervention group conducted a 10-week progressive eccentric training program followed by a weekly seasonal program, whereas players in the control group followed their usual training program. The main outcome measures were numbers of overall, new, and recurrent acute hamstring injuries during 1 full soccer season.
  
  
  RESULTS
  Fifty-two acute hamstring injuries in the control group compared with 15 injuries in the intervention group were registered. Comparing intervention versus the control group, overall acute hamstring injury rates per 100 player seasons were 3.8 versus 13.1 (adjusted rate ratio [RR], 0.293; 95% confidence interval [CI], 0.150-0.572; P < .001). New injury rates per 100 player seasons were 3.1 versus 8.1 (RR, 0.410; 95% CI, 0.180-0.933; P = .034), whereas recurrent injury rates per 100 player seasons were 7.1 versus 45.8 (RR, 0.137; 95% CI, 0.037-0.509; P = .003). Number needed to treat [NNT] to prevent 1 acute hamstring injury (new or recurrent) is 13 (95% CI, 9-23) players. The NNT to prevent 1 new injury is 25 (95% CI, 15-72) players, and NNT to prevent 1 recurrent injury is 3 (95% CI, 2-6) players.
  
  
  CONCLUSIONS
  IN male professional and amateur soccer players, additional eccentric hamstring exercise decreased the rate of overall, new, and recurrent acute hamstring injuries.
authors.affiliation: Department of Orthopaedic Surgery, Amager Hospital, Italiensvej 1, Copenhagen, Denmark. jesper.petersen@dadlnet.dk
authors.forename: Jesper
authors.initials: J
authors.lastname: Petersen
authors.forename: Kristian
authors.initials: K
authors.lastname: Thorborg
authors.forename: Michael Bachmann
authors.initials: MB
authors.lastname: Nielsen
authors.forename: Esben
authors.initials: E
authors.lastname: Budtz-Jørgensen
authors.forename: Per
authors.initials: P
authors.lastname: Hölmich
mesh_terms: D000328:Adult; D056352:Athletes; D001265:Athletic Injuries / Q000517:prevention & control*; D006801:Humans; D007869:Leg Injuries / Q000517:prevention & control*; D008297:Male; D052580:Muscle Stretching Exercises / Q000379:methods*; D018482:Muscle, Skeletal / Q000293:injuries; D055070:Resistance Training / Q000379:methods*; D012916:Soccer / Q000293:injuries*; D013708:Tendon Injuries / Q000517:prevention & control; D016896:Treatment Outcome; D055815:Young Adult