Recovery of the Medial Elbow Joint in the 24-Hour Period After Repetitive Pitching in High School Players

Background: Repetitive pitching causes immediate changes in the medial elbow joint. However, the recovery process from these changes is not clear. Purpose/hypothesis: The purpose of this study was to investigate the recovery of the medial elbow joint in the 24-hour period after pitching. The hypothesis was that while some recovery will occur at 24 hours after repetitive pitching, this would not be a complete return to baseline. Study design: Controlled laboratory study. Methods: A total of 26 high school baseball pitchers participated (mean age, 16.0 +/- 0.5 years). Participants threw 100 pitches (5 sets of 20 pitches). Medial elbow joint width as well as strain ratios of the ulnar collateral ligament (UCL) and forearm flexor-pronator muscles (FPMs) were measured and followed for 24 hours after pitching. The data before pitching and at each time point after pitching were compared. The standard error of measurement (SEM) and minimal detectable change with 95% confidence interval (MDC95) were calculated using measurements before pitching. Results: The medial elbow joint width significantly increased by 0.84 mm immediately after pitching (P < .05), but this was not maintained at 24 hours. The UCL strain ratio significantly decreased by 1.64 immediately after pitching (P < .05), but this was not maintained at 18 hours after pitching. The strain ratio of the FPMs significantly decreased by 0.09 immediately after pitching (P < .05) but significantly increased by 0.13 at 24 hours (P < .05). The SEM for medial elbow joint width was 0.06 mm, and the MDC95 was 0.18 mm (maximum change: 0.84 mm immediately after pitching). The SEM for UCL strain ratio was 0.85, and the MDC95 was 2.35 (maximum change: 1.64 immediately after pitching). The SEM for strain ratio of the FPMs was 0.08, and the MDC95 was 0.22 (maximum change: 0.13 at 24 hours). Conclusion: After 100 pitches, stability against elbow valgus laxity recovered within 24 hours. UCL and FPMs showed statistical characteristic changes, but those changes were within the minimal detectable change. Clinical relevance: Pitchers' medial elbow joint tissue recovered to baseline at 24 hours after pitching. This suggests that it may be acceptable to resume low-intensity throwing after a 24-hour rest period after 100 repetitive pitches while also considering the condition of the rest of the body.