Fastball Velocity In Professional Baseball: Relationships With Trunk Rotation, D2 Flexion, And D2 Extension

In Major League Baseball (MLB), fastball velocity is increasingly emphasized as a component of pitching success. Effective training programs should incorporate exercises that influence velocity. PURPOSE: To evaluate the effects of trunk rotation and D2 flexion and extension on fastball velocity in MLB pitchers. METHODS: We enrolled 28 MLB pitchers to perform a standardized test on a Proteus Motion device (Proteus Motion, USA). Testing consisted of 5 repetitions on the following exercises: straight arm trunk rotation in the dominant throwing direction (12 lb), D2 flexion (shoulder flexion, abduction, and external rotation) on the dominant arm (6 lb), and D2 extension (shoulder extension, adduction, and internal rotation) on the dominant arm (6 lb). Averages of peak power in watts (W) and peak acceleration in m/s2 were recorded across the 5 repetitions. Simple linear regression models tested the effect of power and acceleration in each exercise on subsequent in-game fastball velocity from official MLB reports. RESULTS: Subjects were 29.5 ± 4.1 years of age with a height of 192.0 ± 6.0 cm and weight of 96.7 ± 9.2 kg. Their MLB careers spanned 4.1 ± 3.1 seasons at the time of testing. Proteus performances were: trunk rotational power (294.8 ± 50.3 W) and acceleration (15.1 ± 3.5 m/s2), D2 flexion power (117.5 ± 18.8 W) and acceleration (10.2 ± 3.5 m/s2), and D2 extension power (103.3 ± 15.2 W) and acceleration (7.1 ± 2.4 m/s2). Fastball velocity was 92.6 ± 2.6 mph. Significant predictors of velocity were trunk rotational acceleration (r2 = 0.176; β = 0.307; p = 0.026; 95% CI: 0.039, 0.576), D2 flexion power (r2 = 0.170; β = 0.057; p = 0.029; 95% CI: 0.006, 0.107), D2 extension power (r2 = 0.387; β = 0.106; p < 0.001; 95% CI: 0.052, 0.159), and D2 extension acceleration (r2 = 0.350; β = 0.649; p < 0.001; 95% CI: 0.293, 1.005). Non-significant predictors were trunk rotational power (p = 0.155) and D2 flexion acceleration (p = 0.134). CONCLUSION: Among the exercises tested, dominant arm D2 extension was the most robust predictor of fastball velocity. Athletes and coaching personnel may consider incorporation of this exercise into conditioning programs aimed at increasing fastball velocity.