Throwing Load Does Not Impact Musculoskeletal Measures around Competitive Pitching in Adolescent Baseball Pitchers
Baseball pitching load is linked to injury in adolescent baseball athletes, however, it is unclear if pitch counts are a good indicator of total upper extremity load during baseball pitching. The purpose of this study is to 1) determine the recovery time-course of 8 musculoskeletal variables after a single live pitching bout and 2) determine the association 9 between pitch counts, rating of perceived exertion, and arm-specific session rating of perceived 10 exertion on musculoskeletal changes after live game pitching in adolescent baseball athletes. Cross Sectional Competitive Baseball Games 36 adolescent baseball pitchers (16.1±0.9 years, 178.2±10.4 cm, 71.5±10.2 kg) Internal (IRROM) and external (ERROM) shoulder range of motion, internal (IRPF) and external (ERPF) shoulder rotation peak force, and infraspinatus cross sectional area (CSA) and echo intensity (EI) were collected prior to pitching (PRE), immediately after pitching (POST), and on days 1 (D1), 3 (D3), and 5 (D5) after pitching. Pitch count and rating of perceived exertion (RPE) was collected during the pitching bout, and an arm-specific session rating of perceived exertion (aRmPE) score was calculated as the product of pitch count and RPE. Linear mixed models were used to determine the recovery time-course on both arms and to determine the association between the load variables (pitching count, RPE, aRmPE) and the change in the musculoskeletal variables on the dominant arm. IRROM was highest on D3 (mean difference: 3.31, t=3.12, p=0.019), ERPF decreased at POST(-11.53, t=3.51, p=0.005) and increased at D5 (14.8, t=4.52, p<0.001). IRPF was lowest at POST and highest at D5 (19.14, t=4.18, p<0.001). There was no significant (p>0.057) association between load variables and musculoskeletal variables. Baseball specific pitching load metrics did not predict musculoskeletal changes following live game pitching. Future research should investigate pitching load variables that better predict musculoskeletal changes.ABSTRACT
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