Recovery of Medial Elbow Dynamic Stability 24 Hours After Pitching Under Contraction of the Forearm Flexor-Pronator Muscles in High School Baseball Pitchers

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Abstract
Background: Repetitive pitching causes temporary functional impairment of the medial elbow. The recovery process in medial elbow dynamic stabilizing mechanisms is not clear. Hypothesis/Purpose: This study aimed to investigate the recovery process of the medial elbow dynamic stabilizers over 24 hours after 100 pitches. We hypothesized that while some recovery occurs 24 hours after pitching, there would not be a complete return to baseline. Study Design: Descriptive laboratory study. Methods: A total of 26 high school baseball pitchers participated in this study (mean age, 16 ± 0.5 years). Participants pitched 100 times (5 blocks of 20 pitches). Medial elbow joint width and strain ratio (higher values indicate harder tissue) of the ulnar collateral ligament (UCL) and forearm flexor-pronator muscles (FPMs) under FPM contraction associated with gripping were measured at baseline, immediately after pitching, and at 1, 3, 6, 18, and 24 hours after pitching. The data before pitching and at each measurement time point were compared. Results: Medial elbow joint width during contraction significantly increased immediately after pitching ( P < .05), but this was not maintained at 24 hours. The UCL strain ratio during contraction significantly decreased immediately after pitching ( P < .05), but this was not maintained 18 hours after pitching. The FPMs strain ratio during contraction showed no significant change over time ( P = .747). Conclusion: After 100 pitches, resistance to elbow valgus laxity associated with FPMs contraction temporarily decreases but recovers 24 hours after pitching. In addition, the UCL becomes temporarily vulnerable but recovers by 18 hours after pitching. Clinical Relevance: Baseball pitchers may be allowed to throw low-intensity pitches 24 hours after a pitching session from the perspective of a restoration in dynamic stability. However, rather than determining pitching eligibility based solely on a uniform number of pitches or rest days, objective assessment incorporating medial elbow stabilizing indices may support individualized determination of when to resume pitching.

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