Throwing Load Does Not Affect Musculoskeletal Measures Around Competitive Pitching in Adolescent Baseball Pitchers

Abstract

Context: 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.

Objectives: The purpose of this study is to determine (1) the recovery time-course of musculoskeletal variables after a single live pitching bout and (2) the association between pitch counts, rating of perceived exertion (RPE), and arm-specific session RPE on musculoskeletal changes after live game pitching in adolescent baseball athletes.

Design: Cross-sectional study.

Setting: Competitive baseball games.

Participants or other participants: Thirty-six adolescent baseball pitchers (16.1 ± 0.9 years, 178.2 ± 10.4 cm, 71.5 ± 10.2 kg).

Main outcome measures: Internal and external shoulder range of motion, internal and external shoulder rotation peak force, and infraspinatus cross-sectional area and echo intensity were collected before pitching, immediately after pitching, and on days 1, 3, and 5 after pitching. Pitch count and RPE were collected during the pitching bout, and an arm-specific session RPE 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, arm-specific session RPE) and the change in the musculoskeletal variables on the dominant arm.

Results: Internal shoulder range of motion was highest on day 3 (mean difference: 3.31, t = 3.12, P = .019), and external shoulder rotation peak force decreased immediately after pitching (-11.53, t = 3.51, P = .005) and increased at day 5 (14.8, t = 4.52, P < .001). Internal shoulder rotation peak force was lowest immediately after pitching and highest at day 5 (19.14, t = 4.18, P < .001). No significant (P > .057) association was found between load variables and musculoskeletal variables.

Conclusions: Baseball-specific pitching load metrics did not predict musculoskeletal changes after live game pitching. Future researchers should investigate pitching load variables that better predict musculoskeletal changes.

Keywords: shoulder; workload.