Current State of Baseball Interval Throwing Programs: A Systematic Review of Content, Structure, and Variability of Published Throwing Programs.

Context: There is need for an up-to-date comprehensive review of baseball interval throwing programs in the literature.

Objective: To (1) understand the origin and basis of interval throwing programs; (2) evaluate the content of programs in the peer-reviewed literature including target audience, initiation criteria, throwing specifics, arm care, and performance evaluation metrics; (3) classify these variables as well defined, ambiguous, or missing; and (4) analyze variability in key aspects including starting criteria, length, progression, and completion criteria.

Data sources: Medline, Embase, Cochrane Reviews, Web of Science, and ScopusStudy Selection:The full text of studies, in English, had to be available. Included studies had to contain a complete interval throwing program designed for baseball players.

Study design: Systematic review.

Level of evidence: Level 4.

Data extraction: Initial screening was conducted based on article title and abstract. Full text of the remaining articles was evaluated for fulfillment of inclusion criteria.

Results: Nine studies initially met inclusion criteria. The programs' comprehensiveness was poor, with a mean Interval Throwing Program Checklist score of 20 (range 14-23) on a scale of 0 to 30. There were a variety of components, including progressive long toss, weighted ball, and throwing mechanics exercises. The programs identified had significant heterogeneity in duration, intensity, progression, and focus. Overall, there was a significant lack of attempts at validation or formal study of efficacy for published throwing programs.

Conclusion: Current published interval throwing programs are mostly variations of an original program published many years ago and were based on principles of progressive loading with pain as sign of injury that should be monitored carefully. However, these programs have minimal clinical validation and objective measures to quantify their effectiveness. This work identifies several limitations in the current literature and can serve as a foundation for future development of evidence-based interval throwing programs.