Acute To Chronic Workload Monitoring In Collegiate Baseball Pitchers During Preseason

PURPOSE: Upper extremity injuries are common in baseball spanning from youth through professional leagues, especially in preseason. Although there are some arbitrary guidelines for number of throws during practices and games, there is no current information on workload during preseason in baseball pitchers. The purpose of this study was to quantify weekly workload for pitchers in a six-week preseason in a collegiate baseball team. METHODS: Nine baseball pitchers wore a single inertial measurement unit on the forearm during all training sessions of preseason. Movements were captured at 100 Hz and classified as a throw when the forearm velocity was greater than 800°/second. Peak angular velocity was exported for each throw and total workload was calculated as the median angular velocity multiplied by total throws for each day. Chronic workload was calculated as the average workload across all six weeks and acute workload was calculated as the average seven-day workload. Acute to chronic workload ratio (ACWR) was calculated for each week. Paired t-tests and Cohen’s d effect sizes were used to compare weekly ACWR workload. RESULTS: An average of 1651.11 ± 738.62 were thrown by each participant throughout the preseason at an average angular velocity of 1968.33 ± 266.48 m/s. Participants had significantly reduced ACWR on week 2 (p = 0.048; d = 1.07) and week 4 (p = 0.042; d = 1.19) compared to week 6. CONCLUSIONS: ACWR during the final week of preseason was significantly higher compared to two previous weeks of preseason, suggesting that there may be a need to reduce overload during the final week of preseason. Increased workload over a short time may be associated with greater upper extremity injuries during preseason in collegiate baseball. Monitoring pitching workload using peak angular velocity through a single IMU may provide valuable insight to the sports performance team to prevent chronic overuse injury. Additionally, this can be used to design a progressive overload training during preseason.