{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,21]],"date-time":"2026-08-21T12:37:04Z","timestamp":1787315824317,"version":"build-2736575974"},"reference-count":40,"publisher":"SAGE Publications","issue":"6","license":[{"start":{"date-parts":[[2024,6,1]],"date-time":"2024-06-01T00:00:00Z","timestamp":1717200000000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"DOI":"10.13039\/100007270","name":"university of michigan","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100007270","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["journals.sagepub.com"],"crossmark-restriction":true},"short-container-title":["Orthopaedic Journal of Sports Medicine"],"published-print":{"date-parts":[[2024,6]]},"abstract":"<jats:sec>\n                    <jats:title>Background:<\/jats:title>\n                    <jats:p>Ulnar collateral ligament (UCL) injuries in youth pitchers continue to be concerning despite the institution of pitch count limits. Flexor-pronator mass fatigue can lead to diminished dynamic stability, resulting in greater stress on the UCL.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Purpose\/Hypothesis:<\/jats:title>\n                    <jats:p>To evaluate fatigue of the flexor-pronator mass by assessing changes in medial elbow laxity; noninvasively characterizing alterations in muscle glycogen; and identifying changes in subjective fatigue, strength, range of motion (ROM), pitching velocity, and accuracy with increasing pitches thrown by youth pitchers to their recommended 75-pitch count limit. It was hypothesized that, with increased pitches, medial elbow laxity would increase and that the glycogen content of the flexor-pronator mass would decrease.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Study Design:<\/jats:title>\n                    <jats:p>Descriptive laboratory study.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods:<\/jats:title>\n                    <jats:p>Healthy male pitchers aged 10 years (n = 22) threw 3 sets of 25 pitches with 12 minutes between sets (3 timepoints). Bilateral ulnohumeral joint gapping was measured by applying a standardized valgus force and utilizing ultrasound imaging. Relative changes in muscle glycogen in the bilateral flexor carpi radialis (FCR), and the flexor digitorum superficialis\/flexor carpi ulnaris (FDS\/FCU) muscles were measured with ultrasound software and recorded as fuel percentiles. Additional measures obtained included subjective fatigue, strength, ROM, velocity, and accuracy.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results:<\/jats:title>\n                    <jats:p>There were no differences in medial elbow joint-line gapping between the throwing and nonthrowing arms or between timepoints. The throwing arm demonstrated a significant decline in fuel percentile of the FCR from baseline to after 75 pitches ( P = .05). There were no differences across timepoints for FDS\/FCU fuel percentile values. Fatigue measurements for both arms were significantly higher at all timepoints compared with baseline ( P\u2264 .03). Grip strength of the dominant arm after 75 pitches was decreased significantly compared with after 25 pitches ( P = .02).<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion:<\/jats:title>\n                    <jats:p>Although an increase in medial elbow joint gapping was not demonstrated within the recommended 75 pitch count limit in 10-year-olds, a relative decrease in glycogen stores of the flexor-pronator mass did occur, as well as a decrease in grip strength, with increasing subjective fatigue.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Clinical Relevance:<\/jats:title>\n                    <jats:p>This study provides a foundation for further objective testing of physiologic changes that occur with pitching to better guide pitch count limits and improve the safety of young athletes.<\/jats:p>\n                  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