Preseason Workload in Collegiate Baseball Pitchers.

Abstract

Background: 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.

Hypothesis/purpose: The purpose of this study was to quantify the number of throws and workload, as defined by angular velocity, during preseason training in a collegiate baseball season.

Study design: Descriptive Epidemiology Study.

Methods: Nine baseball pitchers wore an inertial measurement unit on the forearm during all preseason training. Movements were captured at 100Hz 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 rolling 28 days average workload and acute workload was calculated as the average seven-day workload. Acute to chronic workload ratio (ACWR) was calculated for each week. A repeated measures ANOVA with pairwise comparisons was used to compare throws, acute workload, and ACWR between weeks. Cohen's d effect sizes were calculated for all significant differences.

Results: The pitchers averaged 1990.6 ± 881.7 throws throughout preseason at an average angular velocity of 1686.2 ± 334.9 m/s. Acute workload was reduced in Week 4 compared to Week 2 (p=0.018, d=1.73) and week 3 (p=0.007, d =2.30). ACWR was above 1.27 on weeks 1,2,3, and 5. ACWR was significantly reduced in week 4 (0.79) compared to week 3 (1.50; p=0.021, d =0.71).

Conclusion: ACWR was above 1.27 for four of the six weeks of preseason, suggesting that there may be a need to reduce workload and progressively build during the preseason. Clinicians should consider monitoring workload during preseason throwing to decrease risk of chronic overuse injuries.

Level of evidence: 2c.