Inter-pitcher and Intra-pitcher Comparisons on the Relationship between Trunk Kinematics and Ball Speed in Collegiate Baseball Pitchers

The three-dimensional trunk movements are considered to play important roles in producing higher ball speed in baseball pitchers. However, the details on how the variations in trunk kinematics within an individual pitcher associate with ball speed are limited.

The purpose of this observational study was to examine the inter- and intra-pitcher relationship between ball speed and the three-dimensional trunk kinematics in sixteen male collegiate baseball pitchers (age; 20.0 ± 1.1 years, height; 1.77 ± 0.06 m, body mass; 78.0 ± 8.0 kg). Kinematic data of 10 maximum effort pitches were obtained for the correlation analyses with ball speeds. The inter-pitcher analysis included the mean values of each kinematic variable, while intra-pitcher analysis included all 10 pitches within each pitcher.

: The inter-pitcher analysis showed a positive correlation between peak trunk throwing-arm side twist angle and ball speed (ρ = 0.64, p < 0.01, 90% confidence interval [0.24, 0.86]). This relationship was also observed for the intra-pitcher analysis in three pitchers; however, each intra-pitcher showed different patterns of correlational relationship between trunk kinematics and ball speed.

The results indicated that the greater trunk throwing-arm side twist may be an important factor for both the group of pitchers and within an individual pitcher to throw with higher ball speed.

Inter- and intra-pitcher relationships between ball speed and the three-dimensional trunk kinematics were different, suggesting that the individuality should be considered along with the general tendency when the baseball pitchers modify their three-dimensional trunk mechanics.