Interval Throwing Programs of Various Duration for Baseball Players Based on Biomechanical Workload Data

Background: Interval throwing programs (ITP) are commonly used while returning from injuries in baseball players. Recent advances in the understanding of the biomechanics and workloads of throwing programs have led to the development of ITPs that allow for a precise and gradual increase in workload to the arm. UCL treatment options continue to evolve and now include various procedures using an internal brace and hybrid approach in addition to traditional reconstruction and nonoperative care. Each variation has different timelines for clinicians to follow. Purpose: The purpose of this paper is to describe four ITP variations of various durations that can be used for a variety of non-operative and postoperative injuries in baseball players. While these programs can be used for a variety of shoulder and elbow injuries, the application of these programs for UCL injuries will be explored. Study Design: Cross-sectional descriptive study. Methods: Elbow varus torque per throw was estimated from a 2nd order polynomial regression derived from a relationship between throwing distance and elbow varus torque, based on a dataset of 238,611 throws collected from healthy collegiate baseball pitchers. This model was then applied to construct 4 ITPs: 7-month progression for UCL reconstruction (with and without a hybrid internal brace), 5-month progression for a UCL repair with internal brace, and two short-term progressions of 12-weeks and 6-weeks for nonoperative injuries. For each program, individual throws were assigned estimated torque values to calculate cumulative workload (daily, chronic, and acute), and acute-to-chronic workload ratio (ACWR). These values were plotted over time to evaluate workload progression. Results: The 6-week program had a final chronic workload of 7.6 and stayed in the ACWR optimal range (0.7-1.3) the entire time. The 12-week program had a final chronic workload of 7.8 and stayed in the optimal ACWR range 98% of the time. The 5-month program finished with a chronic workload of 10.0 and stayed in the optimal range 95% of the program. The 7-month had a final chronic workload of 10.8, and stayed in the optimal range for 91% of the program. Conclusion: The four variations in ITPs each showed a gradual ramp-up of chronic workload over the duration of the program while maintaining within the recommended range of ACWR. These ITPs may be used to gradually build workload in baseball players returning from injuries. Due to the various lengths, the ITPs may be used as models to apply to a variety of common injuries or surgeries of the throwing shoulder and elbow. Level of Evidence: Level 3.