Chronic Effects of Sprint Training With and Without Weighted Vests on Linear and Change of Direction Sprint Performance in Youth Baseball Players

PURPOSE: Sprint training is essential to enhance performance in baseball. This study examined the effects of sprint training with and without a weighted vest on 27-m (30-yd) and 55-m (60-yd) linear and 55-m (60-yd) change-of-direction sprint performance in youth baseball players. METHODS: We conducted an open-label, 2-arm parallel group randomized trial with preintervention and postintervention assessments. Thirty-eight male youth baseball players (13.4 [0.5] y) were randomly assigned to a control group or an experimental group (n = 19 each). Both groups completed a 4-week (12-session) sprint training program. The experimental group trained wearing a vest equivalent to 10% of body mass, whereas the control group trained unloaded. RESULTS: No significant group × time interaction was observed for any sprint outcome (27-m: P = .174, r = .22, 95% CI, -0.01 to 0.45; 55-m: P = .169, r = .23, 95% CI, -0.01 to 0.45; 55-m change of direction: P = .132, r = .25, 95% CI, -0.01 to 0.45). However, all participants improved sprint performance following the intervention, with percentage changes of -1.18% to -1.68% for the 27-m sprint (95% CI, -2.83 to -0.10%), -1.00% to -1.18% for the 55-m sprint (95% CI, -1.82 to -0.31%), and -0.94% to -1.08% for the 55-m change-of-direction sprint (95% CI, -1.62 to -0.28%). CONCLUSION: Under the conditions of a 4-week intervention using a weighted-vest equivalent to 10% of body mass, weighted-vest sprint training did not produce superior improvements compared with unloaded sprint training in youth baseball players.