700 MEP028 – Pre-screening measures to predict shoulder distraction forces in softball pitching

AbstractBackground Higher shoulder distraction forces are related to increased pitch velocities and injury susceptibility among softball pitchers. It is important to determine if clinical pre-screening measures can be used to predict pitchers who will experience higher distraction forces. Objective To determine if hip and shoulder range of motion (ROM) and isometric (ISO) strength predict shoulder distraction forces while controlling for pitch speed and body weight.Design A cross-sectional study.Setting Controlled laboratory setting. Elite Division.Participants Fifty-six softball pitchers (19.9+1.2 yrs.;79.2+11.7 kg;173.1+7.5 cm) who were injury/surgery for the past six months participated.Interventions Pre-screening measures (bilateral hip and throwing shoulder internal (IR) and external rotation (ER) ROM and ISO strength) were the independent variables in the stepwise regression analyses to determine their relationship with shoulder distraction force beyond the effect of body weight and pitch velocity. Main Outcome Measurements Peak throwing shoulder distraction force was measured using an electromagnetic motion capture system and used as the dependent variable in regression analyses.Results The regression model with only pitch velocity and body weight accounted for 29.2% of the variance in peak shoulder distraction force alone. The predictive model was improved by adding trail hip ISO strength ratio (IR/ER) [F(1,52) =4.47, ΔR2=.057, .p = .039]. On average, the model predicted there was a 1-point increase in hip ISO strength ratio for every 187 N increase in peak shoulder distraction force (β = 186.8 p = .039). Conclusions Trail hip ISO ratio (IR/ER) is an influencing factor of peak shoulder distraction force. Specifically, pitchers who present with greater hip IR ISO strength relative to ER ISO strength increase shoulder distraction force without the benefit of an increased pitch velocity. Clinicians should monitor trail hip ISO strength ratios of softball pitchers to mitigate risk of injury.