A prospective cohort study of hamstring injuries in competitive sprinters: Preseason muscle imbalance as a possible risk factor

Background: Hamstring injuries are common in sprinters. Identifying preseason risk factors is essential to target injury-prone athletes and develop injury preventive measures. Objective: To investigate the incidence of hamstring muscle injury in sprinters over an athletic season and to explore the preseason predictor of this injury. Design: Prospective cohort study. Participants: 44 sprinters from the Hong Kong Sports Institute, the Hong Kong Amateur Athletic Association and intercollegiate athletic teams were recruited. Methods: Preseason assessment of hamstring flexibility, concentric and eccentric isokinetic peak torque and peak torque angle were obtained at the beginning of an athletic season. The athletes were followed over 12 months and were asked to report all injuries resulting from training and competition. Results: Eight athletes sustained hamstring injuries over the season. The injury rate was 0.87 per 1000 h of exposure. The incidence of injuries was higher at the beginning of the season, with 58.3% injuries occurring in the first 100 h of exposure. Cox regression analysis revealed that athletes with a decrease in the hamstring : quadriceps peak torque ratio of less than 0.60 at an angular velocity of 180°/s have a 17-fold increased risk of hamstring injury. Conclusion: Performing preseason hamstring : quadriceps peak torque ratio assessments may be useful to identify sprinters susceptible to hamstring injury.