522 MEP027 – Physical factors change the elbow varus torque – ball velocity relationship in collegiate baseball pitchers

AbstractBackground Excessive elbow varus torque (EVT) is the primary biomechanical mechanism of ulnar collateral ligament (UCL) injury in baseball pitchers. The EVT-ball velocity (T-V) relationship is pitcher specific and can help to define UCL injury risk. Modifiable physical factors have the potential to define pitcher-specific variation in the T-V relationship.Objective Identify modifiable physical factors impacting the T-V relationship during pitching.Design Cross-sectional study.Setting NCAA Division-1 (USA) collegiate pitchers, assessed at their respective institutions.Participants Collegiate pitchers (N=87) aged 18 years or older on an NCAA Division-1 roster participated. Pitchers with a current throwing elbow injury or injury in the last 6 months requiring 2 or more weeks of rest were excluded.Assessment of Risk Factors Pitchers threw 5 full effort fastballs from a mound, over regulation distance to a catcher. Physical measures were collected bilaterally for: shoulder and hip passive range of motion (ROM), strength, shoulder rate of torque development (RTD), grip strength, and lumbopelvic stability. Participant bodyweight (kg) was also recorded. Main Outcome Measurements Dependent variable of interest was peak EVT, with ball velocity as a covariate. Results In univariate analyses, for every 1m/s increase in ball velocity, mean EVT increased by 1.51Nm (95%CI=0.66,-2.37;p=0.001). Significant univariate relationships and variables entering the final univariate model are noted in Table 1. Variables that increased EVT while controlling for ball velocity in the final model include grip strength symmetry, stride leg lumbopelvic stability, and bodyweight. Conclusion Several modifiable physical measures impacted the T-V relationship, controlling for ball velocity in both univariate and multivariate analyses. Our model can be used to identify appropriate physical characteristics through which clinicians, coaches and athletes can alter the EVT (and therefore T-V relationship) for a given fastball.View this table:View inline View popup Download powerpoint Abstract 522 Table 1 Univariate and multivariate models are reported. Significant variables in univariate mixed-effects models to predict non-normalized elbow varus torque (P <0.05) Final multivariate linear mixed-effects model* for predicting elbow varus torque. Measures of symmetry were calculated as dominant side – non-dominant side. *AIC = 2478.6; BIC = 2518.8. ** variable is analyzed in log scale, and it is interpreted as every 10% increase in the variable, the