Summary of athletes, interventions, comparators and injuries of included studies
| Study | Athletes | Interventions | Comparator(s) | Number of injuries | Outcome recording |
|---|---|---|---|---|---|
| Askling et al19 | 30 male soccer athletes from 2 premier league teams in Sweden. Goalkeepers, injured players and players with chronic hamstring problems were excluded from the study | “Yo-Yo” flywheel ergometer (n=15). 16 sessions of specific hamstring length training, every 5th day for the first 4 weeks, and every 4th day during the last 6 weeks (total of 10 training weeks) | The training and control groups (n=15) followed the same protocol with the only exception being that the training group received additional specific hamstring training during phase 1. Intervention was for 10 weeks period | Intervention group: 3/15 athletes Control group: 10/15 athletes | Compliance and side effects: (muscle soreness/symptoms in training) recorded individually by athlete. Injuries: recorded by team training staff (not part of study) |
| Gabbe et al20 | 220 Australian Rules Football athletes. Athletes were excluded if they had a hamstring injury at the time of recruitment | Nordic Hamstring Exercise (n=114). 12 sets×6 reps with a 10 s rest in between reps and 2–3 rest between sets. 5-session programme over a 12-week period. The first three sessions were 2 weeks apart during the last 6 weeks of preseason. The final two sessions were 3 weeks apart during the first weeks of the season | Control group (n=106): gastrocnemius stretch in standing (30 s); hip flexor stretch in kneeling (30 s); hamstring stretch in supine (30 s); hamstring stretch in sitting (30 s); lumbar spine rotation in supine (15 s). Interventions were prescribed 5 times during one 12-week period. | Intervention group: 10/114 athletes Control group: 8/106 athletes | Compliance and side effects: Each session was supervised by study personnel. Injuries: monitored by club officials and medical staff. Injury surveillance form filled out/injury recorded by team physiotherapist not blinded to allocation of player to specific group |
| Engebretsen et al21 | 37 male soccer athletes from the 1st, 2nd, or top of the 3rd Norwegian League. Athletes divided into high (previous injury) and low (no previous injury) risk groups | Nordic Hamstring exercise (n=24). Week 1: (1 session per week with 2 sets of 5 reps), week 2: (2 sessions per week with 2 sets of 6 reps), week 3: (3 sessions per week with 3 sets of 6−8 reps), week 4: (3 sessions per week with 3 sets of 8–10 reps), weeks 5–10: (3 sessions per week with sets of 12, 10, and 8 reps) | Control group (n=13) continued with their normal training schedule throughout the 10-week cycle | Intervention group: 5/24 athletes Control group: 1/13 athletes | Compliance and side effects: Individual players recorded exercises performed. Injuries: team physical therapist instructed exercises and recorded injuries (blinding unknown, but assumed they were not since they provided intervention, etc.) |
| Petersen et al22 | 942 Danish professional and amateur soccer athletes. Detail of previous hamstring injuries during past 12 months was recorded | Nordic Hamstring Exercise (n=461). Along with normal training performed 27 sessions of Nordic hamstring exercise over 10 week span. Week 1: (1 session per week with 2 sets of 5 reps), week 2: (2 sessions per week with 2 sets of 6 reps), week 3: (3 sessions per week with 3 sets of 6–8 reps), week 4: (3 sessions per week of 8–10 reps), week 5–10: (3 sessions per week with 3 sets of 12–10–8 reps). After week 10 the players continued to do 1 session per week of 3 sets of 12–10–8 reps | Control group (n=481). Continued with their normal training schedule throughout the 10-week cycle | Intervention group: 15 (12 new and 3 recurrent)/461 athletes Control group: (52 (32 new and 20 recurrent)/481 athletes | Compliance and side effects: Supervised by team coaches. Injuries: team physiotherapist recorded injuries. Recurrence of previously recorded injuries in registration period was not included to avoid recording same injury more than once |