Shoulder stretching versus shoulder muscle strength training for the prevention of shoulder and elbow injuries among high school baseball pitchers

Shoulder and elbow injuries seriously affect baseball players. We investigated the non-inferiority (NI) hypothesis that external rotation strength training presents no inferior effect when compared with sleeper stretching for shoulder and elbow injury prevention among high school baseball pitchers. In this randomized, active-controlled, open-label, NI study, 79 pitchers were randomly allocated to the stretching and muscle-training groups and performed a specific exercise every night. We applied sleeper stretching as an active control. Elbow and shoulder injury tracking was performed for 150 days. Kaplan–Meier survival curves were generated and the hazard ratios (HR) for injury occurrence using multivariate Cox regression were calculated. The log-rank test was used for between-group comparisons of survival distributions. A one-sided NI test using a fixed 10% NI margin was performed (significance level, P  = 0.025). Sixty-two and 51 pitchers were included in the analysis of the stretching and training groups, respectively, with 22.6% (n = 14) and 9.8% (n = 5) injury rates, respectively. The NI test revealed lower incidence in the muscle-training group with pre-specified NI margin ( P  < 0.001). The HR was 0.489 in the muscle-training group based on the stretching group. In high school baseball pitchers, external rotation muscle strength training for baseball-related arm injury prevention was non-inferior to stretching.