The Influence Of Arm Slot, Stride Length, And Stride Angle On Baseball Throwing Velocity

Throwing velocity (TV) is influenced by numerous factors. Better understanding of pitching mechanics can aid coaching staff in designing optimal training programs. PURPOSE: To evaluate the effect of stride length, stride angle, and arm slot on TV across different levels of play. METHODS: We enrolled 100 baseball pitchers from 3 different populations: high school (n = 7), college (n = 75), and professional (n = 18). Following a standardized warmup, each subject performed 5 pitches that were analyzed using high-speed motion capture cameras (OptiTrack Prime 17 W). Stride length, stride angle, and arm slot were exported. Pitch velocity was captured using a Stalker Sport radar system. We estimated differences in play levels using one-way ANOVA. Linear regression measured the effects of kinematic parameters on TV holding confounders constant. RESULTS: Across the total sample, subjects were 21.4 ± 2.3 years old, 185.3 ± 7.2 cm tall, and weighed 90.7 ± 10.1 kg. Stride length was 83.6 ± 5.8% of height (70.4 to 99.6%), stride angle was 1.9 ± 5.9° (-9.2 to 13.3°), and arm slot was 42.2 ± 7.4° (14.2 to 59.8°); none of these differed between levels of play (p > 0.125). TV was 84.8 ± 4.7 mph (71.3 to 94.0 mph) and was different between play levels (p = 0.002): high school (79.6 ± 4.7 mph), college (84.8 ± 4.4 mph), and professional (86.8 ± 4.8 mph). Stride length (p = 0.089), stride angle (p = 0.065), and arm slot (p < 0.001) were associated with TV. Height was related to stride length (p = 0.060) and weakly associated with arm slot (p = 0.092), but not stride angle (p = 0.981). Height (p = 0.012) and weight (p = 0.014) were correlated with TV. In the regression analysis, high multicollinearity existed between age and play level; age was retained owing to better significance. Weight (β = -0.043; p = 0.398) and stride angle (β = -0.091; p = 0.208) were insignificant and removed from the model. Holding age (β = 0.665; p < 0.001) and height (β = 15.474; p = 0.007) constant, stride length (β = 21.190; p = 0.003; 95% CI: 7.245, 35.135) and arm slot (β = -0.218; p < 0.001; 95% CI = -0.327 -0.110) were significant predictors of TV (r2 = 0.332; p < 0.001). CONCLUSION: Among pitchers across various play levels, increased TV was predicted by a lower arm slot and longer stride length. These kinematic variables should be included in a standard assessment by coaches and other sport professionals.