Trunk Muscle Function Deficit in Youth Baseball Pitchers With Excessive Contralateral Trunk Tilt During Pitching

Objective: Pitching technique is one of many factors that affect injury risk. Exhibiting excessive contralateral trunk tilt (CLT) during pitching has been linked to higher ball speed but also to increased joint loading. Deficit in trunk muscle strength has been suggested as an underlying cause of this movement pattern. The purpose of the study was to compare trunk muscle strength between youth baseball pitchers with varying degree of CLT during pitching. Design: Cross-sectional study. Setting: Baseball practice fields. Participants: Twenty-eight youth baseball pitchers. Independent Variables: Pitching technique was captured using a video camera. Based on the 2-dimensional trunk contralateral flexion angle, pitchers were categorized into low (30 degrees) CLT groups. Main Outcome Measures: Maximum isometric strength tests for trunk flexion, extension, and bilateral rotation, measured using a dynamometer. Results: The pitchers with high CLT (n = 10) had longer pitching experience (P = 0.014), produced higher ball speed (P = 0.003) compared with the pitchers with moderate (n = 10) and low (n = 8) CLT, but demonstrated greater asymmetry in trunk rotation strength (relative weakness in rotation strength toward dominant side) compared with the pitchers with low CLT (P = 0.015). Conclusions: Excessive CLT may be a strategy that young pitchers learn to achieve higher ball velocity but also may be associated with imbalance between the oblique muscles on dominant and nondominant side, which may be acquired from repetitive pitching. Strengthening and emphasizing the use of dominant side oblique muscles may keep pitchers from leaning excessively during pitching and thus decrease joint loading.

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