Does trunk rotation timing affect shoulder and elbow kinetics in baseball pitching? A systematic review with meta-analysis

Introduction: Biomechanical studies found that the early onset timing of upper trunk rotation was associated with higher upper-limb kinetics in baseball pitching. However, no systematic review has been performed to synthesize the current evidence. Objective: To synthesize the findings from primary studies on the effects of trunk rotation timing on arm kinetics during pitching. Methods: Six databases were systematically searched from inception to 16th January 2025. Quality assessment was performed using a critical appraisal tool based on the STROBE guidelines. Data from studies with homogeneous outcome measures and analysis methods were pooled through meta-analysis. Results: A total of 13 descriptive laboratory studies were included. Participants were predominantly young male pitchers. Meta-analysis revealed significant differences in peak elbow varus torque and shoulder proximal force between late and early upper trunk rotators. Conclusions: Late timing of upper trunk rotation relative to pelvis may reduce excessive elbow varus torque and shoulder proximal forces.