Immediate changes in thoracic spine mobility after repetitive pitching in high school baseball players: A randomized controlled trial

BACKGROUND: Thoracic spine mobility is essential for optimal pitching mechanics and injury prevention in baseball players. While shoulder and hip range of motion (ROM) changes after pitching have been reported, there is a lack of evidence regarding immediate changes in thoracic spine ROM after pitching. OBJECTIVE: To investigate the immediate effects of repetitive pitching on thoracic spine extension and rotation ROM in high school baseball players and to identify which assessment method is most sensitive to these changes. DESIGN: Randomized controlled trial. SETTING: High school baseball fields. PARTICIPANTS: Thirty-four male high school baseball players were randomly assigned to a pitching group (n = 17) or a control group (n = 17). Players with prior elbow surgery or recent injuries were excluded. INTERVENTIONS: The pitching group performed 100 maximum-effort fastballs, and the control group rested for an equivalent duration. MAIN OUTCOME MEASURES: Thoracic kyphosis angle, upper and lower trunk extension ROM, total trunk extension ROM, and six thoracic mobility tests were assessed before and after the intervention. The primary outcome was dominant-side thoracic rotation ROM measured by the side-lying rotation test. RESULTS: A significant group × time interaction was observed for dominant-side rotation in the side-lying rotation test (p = .015). Post hoc analysis revealed a significant increase in ROM after pitching in the pitching group (mean difference [pre-post] = -3.4°; p = .004; 95% CI: -5.675 to -1.266). No statistically significant correlation was found between ball velocity and dominant-side rotation ROM (r = 0.454, p = .067), although a moderate-to-large effect size was observed. CONCLUSIONS: Repetitive pitching acutely increases thoracic rotation ROM toward the throwing side in high school baseball players, detectable by the side-lying rotation test. This test may serve as a practical tool to monitor pitching-induced mobility changes relevant to performance and injury prevention.