Quantitative and qualitative disparities exist between baseball and softball peer-reviewed pitching-related literature: a systematic review from 1990 to 2020

BACKGROUND: Baseball and softball are popular sports with similar rates of injury, especially among pitchers. However, parity between the two sports is lacking, as baseball receives greater research attention than softball. The purpose of this study was to describe the discrepancy between baseball and softball in terms of quantity and quality of research. We hypothesized baseball literature would outnumber softball literature, be published in higher-impact journals, and be of higher quality. METHODS: A systematic review was performed to identify original research articles related to baseball and softball from 1990 to 2020. Articles pertaining to pitching were identified via literature searches of PubMed, the Physiotherapy Evidence Database, the Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Central Register of Controlled Trials and further screened by two independent reviewers. Age group studied, journal impact factor, type of research, and level of evidence were compared between pitching-related baseball and softball articles. Injury-related studies were also subanalyzed, and a meta-analysis was performed to assess rates of shoulder and elbow injuries between baseball and softball pitchers. RESULTS: There were 813 baseball publications and 158 softball publications that met our inclusion criteria. More baseball articles were published per year than softball (5:1, P < .001). Baseball had 368 articles related to pitching, while softball had significantly fewer at 49, and there were more baseball pitching articles published per year than softball pitching articles (7.5:1, P < .001). Pitching-related baseball articles were published in journals with a higher mean impact factor than softball pitching articles (3.1 vs. 2.0, P = .049). There was no difference in methodological index for non-randomized studies criteria for rigorous reporting (P = .678), and among all groups, most articles were level III evidence. Baseball pitching articles included more clinical articles than softball pitching articles (63% vs. 43%, P = .004). Despite the fact that softball pitchers have an odds ratio of shoulder and elbow injury slightly higher than baseball (4.02 vs. 3.60), injury-related studies focused on baseball outnumbered softball studies 7 to 1. CONCLUSION: Softball is under-represented in the literature when compared to baseball with over 5 times fewer peer-reviewed research articles, despite having slightly higher shoulder and elbow injury rates than baseball. Pitching-related softball articles are nearly 8 times less frequent compared to baseball pitching articles and published in journals with a lower impact factor. Further research directed at softball is important to provide evidence-based injury prevention, practice guidelines, and treatment decisions.