BACKGROUND: Exit velocity (EV) is a measure of the speed with which a baseball leaves a baseball bat immediately after a batter makes contact during the swing. It is commonly used to assess power and hitting performance in college and professional baseball. However, few studies have examined if hitting biomechanics are better in hitters with higher EVs. Therefore, this study examined differences in swing biomechanics for hitters with above vs. below-average EV. METHODS: All data were collected and published freely online by The OpenBiomechanics Project performed by Driveline Baseball. Eighty-seven male participants (age 19.98 ± 2.11) of varying skill levels (12 high school, 66 college, 4 independent league, 5 minor league) performed four to nine swings. During each swing, a K-Motion hitting vest and multiple high-speed cameras coupled with fifty-five markers recorded data relating to bat and body movements. The swing with the highest EV was used for analysis. The average EV of the data set was calculated (94.77 ± 6.20 mph), and participants were then grouped into above and below-average categories (n = 54 above average, n = 33 below average). An independent samples t-test compared body mass, height, age, bat weight and length, launch angle after contact, distance hit, pitch angle, and maximum bat, hand, upper arm, pelvis, torso, and center of gravity velocities between groups. RESULTS: Body mass (p < 0.001), height (p = 0.017), bat weight (p = 0.001), bat length (p = 0.001), maximum bat speed (p < 0.001), and hand speed (p = 0.038) were all greater for the above-average group. No other significant differences existed (p < 0.057). CONCLUSIONS: These results suggest that hitters with an above-average EV are heavier, presumably with more muscle mass, use larger bats, and have faster bat and hand speed during the swing. Based on the greater body mass and bat size, it is possible one of the main factors separating above versus below-average hitters could be greater muscle mass and strength, rather than swing mechanics, both of which aid to increase movement velocity. However, kinetic and kinematic variables during baseball should be further studied in conjunction with measures of muscle mass and strength to better understand the differences between above versus below-average hitters.

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