Relationship between workload and throwing injury in varsity baseball players

Objectives: In this study we describe the first analysis of the relationship between acute-to-chronic valgus workload ratio (ACVR) and injury in baseball. Design: Observational study. Setting: Competitive, team sport. Participants: Eighteen, elite male baseball players (aged 17.0 +/- 0.7 year, height 185 +/- 5.7 cm, and mass 85.2 +/- 7.6 kg) competing at the varsity level participated in this six-month study. Each player wore the motusTHROW (TM) sleeve and sensor during pre-season training and the entire 2017 regular season. Main outcome measures: ACVR and injury. Results: Overall there were a total of ten injuries recorded throughout the 2017 season amongst those wearing the sleeves, including six throwing-related injuries. Over 159 days of throwing, a total of 171,703 throws, and 1307 exposures were captured with the motusTHROW (TM) sensors. Five of the six throwing-related injuries occurred when athletes had an ACVR greater than 1.27, which marks the 75th percentile across all observations. Results from logistic regression suggested that ACVR was significantly related to injury occurrence (p < .05). This resulted in an odds ratio of 15.2 and a risk ratio of 14.9, meaning that ACVR ratios above 1.27 were 14.9 times more likely to result in injury than ACVR ratios below 1.27. Conclusions: Logistic regression reveals a significant relationship between ACVR and injury occurrence such that high ACVRs may increase injury risk. (C) 2019 Elsevier Ltd. All rights reserved.