Effects Of Wrist Pronation Angle, Elbow Flexion Angle, And Elbow Extension Velocity On Fastball Speed

Baseball pitchers are at risk for developing injuries in the shoulder and elbow, with an increase in ulnar collateral ligament repairs in recent years. Better understanding of pitching kinematics may help coaches and other healthcare professionals design appropriate conditioning and treatment programs. PURPOSE: To test the influence of wrist pronation angle (WPA), elbow flexion angle (EFA), and elbow extension velocity (EEV) on throwing velocity (TV) in adult baseball pitchers. METHODS: We used a high-speed video capture system (OptiTrack Prime 17 W) to evaluate the throwing mechanics of 100 baseball pitchers (18 professional, 75 college, 7 high school), exporting WPA at foot plant, EFA at foot plant, maximum EFA, and maximum EEV. TV was captured using a Stalker Sport radar system. Following a standardized throwing warm-up, each pitcher performed 5 consecutive throws. Composite values from these throws were calculated. Linear regression tested the effect of arm mechanics on TV holding height and age constant. RESULTS: Across all play levels, subject age was 21.4 ± 2.3 years, height was 185.3 ± 7.2 cm, and weight was 90.7 ± 10.1 kg. WPA at foot plant was 12.2 ± 18.0°, EFA at foot plant 103.1 ± 16.1°, maximum EFA was 118.0 ± 10.0°, and maximum EEV was 2,464.4 ± 235.0°/s. TV was 84.8 ± 4.7 mph, and it differed across play levels (high school: 79.6 mph, college: 84.8 mph, professional: 86.8 mph; p = 0.002). Height (r = 0.250; p = 0.012) and age (r = 0.331; p < 0.001) were related to TV. Without controlling for confounders, kinematic variables related to TV were WPA at foot plant (r = 0.215, p = 0.031) and EFA at foot plant (r = -0.183, p < 0.001). TV was unrelated to maximum EFA (r = -0.140, p = 0.165) or maximum EEV (r = 0.088, p = 0.385). Holding age and height constant, regression analysis found no significance in any of the four kinematic parameters: EFA at foot plant (β = -0.030; p = 0.278), maximum EFA (β = -0.032; p = 0.479), maximum EEV (β = 0.003; p = 0.174), and WPA at foot plant (β = 0.040; p = 0.109). CONCLUSION: TV was correlated with WPA and EFA, but these relationships were eliminated by the addition of covariates. Accordingly, training pitchers to use safer arm mechanics might preserve joint and tissue integrity without affecting fastball velocity.