Adam R. Nebel1, Anthony Fava1, Billy Lozowski1, Yuki Yanagita1, Thomas van Hogerwou2, Gretchen D. Oliver, FACSM1. 1Auburn University, Auburn, AL. 2Technical University of Delft, Delft.

Background: Increased shoulder distraction force during a baseball pitch may make a pitcher susceptible to rotator cuff or glenohumeral labrum injuries. A precursor to a pitching injury may be pain experienced at the throwing arm. Purpose: To compare peak shoulder distraction (PSD) forces in youth baseball pitchers with and without upper extremity pain when throwing a fastball. A secondary purpose was to determine if differences exist in the range of PSD forces between pain and pain-free groups. Methods: Thirty-six baseball pitchers were separated into pain-free (13.2 ± 1.7 yrs.; 164.4 ± 13.8 cm; 56.7 ± 15.2 kg; n = 17) and pain (13.3 ± 1.8 yrs.; 164.9 ± 12.5 cm; 56.7 ± 14.0 kg; n = 19) groups. Pitchers in the pain group had identified in a health history questionnaire that they experience pain in their upper extremity related to throwing a baseball. Pitching mechanics for a minimum of two fastballs per pitcher were recorded with an electromagnetic tracking system and motion capture software sampling at 240Hz. PSD force was normalized to the pitcher’s body weight (%BW), with intra-pitcher mean PSD (mPSD) calculated using each pitcher’s average PSD of the selected trials. Trials with the highest recorded PSD were used as max effort PSD (PSDmax). Intra-pitcher PSD range (rPSD) was calculated by finding the difference in the PSD force between the trial with the highest and lowest observed force. Statistical significance was set a priori to p < .05. Results: Mean PSD force was 114.96 ± 35.40%BW for the pain group and 96.62 ± 30.36%BW for the pain-free group. A one-tailed Mann-Whitney U-test revealed that pitchers in the pain group exhibited significantly higher PSDmax forces than those in the pain-free group (p = .04363, U = 107, z = 1.71). The mPSD forces (p = .08226, U = 117, z = 1.39425) and rPSD forces (p = .0537, U =103, z =1.606) were not significantly different between groups. Conclusion: The PSDmax force, when normalized to a pitcher’s body weight, was higher in the group experiencing pain while throwing fastballs than the group who reported they were pain-free while throwing. Further studies are needed to identify what other kinetics and kinematics may differ between pain and pain-free pitchers.

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