The Nordic Hamstring Exercise (NHE) has been used for the prevention of hamstring injury among soccer players. Many studies have shown the effect of NHE among professional soccer players but there are a few studies for adolescent amateur soccer players. The purpose of this study was to clarify the effect of the NHE on preventing hamstrings injury by calculating hamstring injury rate and time-loss injury rate in adolescent amateur soccer players.

The subjects were high school soccer players in Japan. They were clustered as a team and randomly assigned into two groups; 156 in the NHE group and 103 in the control group. All of the subjects were measured by physical function, practice and game hour per day, injury detail if happened and time-loss hour for soccer. Hamstring injury rate and time-loss injury rate were calculated. Two groups were compared by unpaired t test at significant level of 5%.

Hamstring injuries occurred in 7 cases; 4 in the NHE group and 3 in the control group. Hamstring injury rate was 0.09 per 1000 athlete-hours in the NHE group while 0.10 in the control group. The relative risk of hamstring injury rate was 1.14. Time-loss hamstring injury rate was 0.11 per 1000 athlete-hours in the NHE group while 0.52 in the control group. The relative risk of time-loss hamstring injury rate was 4.54.

As an effect of the NHE in high school soccer players, time-loss injury rate had stronger impact than the hamstring injury rate. These results indicated that the NHE in high school soccer players may had reduced the severity of hamstrings injury without changing injury rate. It is suggested that importance of investigating hamstrings injury prevention in adolescent amateur soccer players using time-loss injury rate in future.