Effects Of Wrist Position At Stride Foot Contact On Joint Moments In Baseball Pitching

Shoulder and elbow joints endure high stress during pitching, leading to injuries. While various kinematic variables have been linked to higher joint moments, the effects of the throwing arm position at stride foot contact (SFC) on joint moments are not well understood despite being a common coaching point for young pitchers. PURPOSE: The objective of this study was to examine how the pitcher’s arm position at SFC affects the joint moments in high school/collegiate pitchers by quantifying the arm position based on the height of the wrist (= endpoint of the throwing arm) relative to the shoulder. METHODS: 75 high school (n = 60) and collegiate (n = 15) pitchers participated. The pitching motion was captured using a motion capture system (600 Hz). Upper torso and shoulder angles and shoulder internal rotation (IR) and elbow varus moments were calculated. Based on the wrist height relative to the shoulder at SFC, participants were categorized into high (>5 cm above shoulder), level (within 5 cm of shoulder height), and low (>5 cm below shoulder) wrist groups. One-way ANOVA and a Bonferroni post-hoc test was used to compare the upper torso and shoulder angles at specific timepoints and peak joint moments between groups. Statistical parametric mapping (SPM) was used to compare shoulder external rotation and upper torso rotation angles between the low and high wrist groups. RESULTS: The high wrist group exhibited higher shoulder IR (p = .039) and elbow varus (p = .024) moments compared to the low wrist group. The SPM showed a significant difference between the two groups in both joint angles (p = <.001 and p = .0018) for the first 70% of the pitching motion (Figure 1). CONCLUSION: High wrist position at SFC was associated with earlier trunk and shoulder rotation, which may have resulted in higher joint moments. Coaching young pitchers to keep the wrist below the shoulder at SFC could be beneficial for reducing the high joint moments placed on the throwing arm.