Department of Orthopaedic Surgery, Lenox Hill Hospital, New York, New York, USA.
Weill Cornell Medical College, New York, New York, USA.
Am J Sports Med. 2022 Jul;50(8):2271-2280. doi: 10.1177/03635465221094323. Epub 2022 May 23.
Early pelvis rotation has been associated with decreased throwing arm kinetics and conventionally was considered a component of proper pitching form in baseball throwers. However, previous assessments of pelvis rotation style have not accounted for confounders such as playing level, anthropometric characteristics, or ball velocity and have not evaluated sufficient sample sizes.
To compare kinetic and kinematic parameters based on pelvis rotation style in high school and professional pitchers.
Descriptive laboratory study.
High school and professional baseball pitchers threw 8 to 12 fastball pitches while being evaluated using 3-dimensional motion capture (480 Hz). These pitchers were 1:1 propensity score matched by age, height, weight, handedness, and ball velocity based on early (<60°) versus late (≥60°) pelvis rotation style at foot contact. A total of 26 kinematic and 10 kinetic parameters were compared between groups. The kinematic parameters were used to conduct a linear regression between early and late pelvis rotation at foot contact.
Pelvis rotation at foot contact was not significantly associated with ball velocity for either high school ( = .243) or professional pitchers ( = .075). No difference was found in elbow varus torque between high school early rotators (57.5 ± 14.9 N·m) and late rotators (51.3 ± 14.7 N·m; = .036) and between professional early rotators (80.1 ± 11.8 N·m) and late rotators (79.0 ± 11.2 N·m; = .663). At foot contact in high school pitchers, stride length increased by 2.1% of body height (B = -0.205; β = -0.470; < .001), trunk rotation increased by 4.2° (B = -0.417; β = -0.488; < .001), and trunk flexion at foot contact decreased by 4.4° (B = 0.442; β = 0.476; < .001) with every 10° increase in pelvis rotation. At foot contact in professional pitchers, stride length increased by 2.3% of body height (B = -0.229; β = -0.478; < .001), trunk rotation increased by 4.3° (B = -0.431; β = -0.515; < .001), and trunk flexion decreased by 4.0° (B = 0.404; β = 0.373; < .001) with every 10° increase in pelvis rotation.
Pelvis rotation at foot contact was associated with several kinematic parameters in both groups and may influence mechanics further along the kinetic chain. Landing open or closed was not significantly associated with throwing arm kinetics or ball velocity for both high school and professional baseball pitchers, contrary to previous thought.
Coaches and players may better focus their efforts on refining other kinematic parameters for enhanced performance outcomes and safe pitching mechanics.
早期骨盆旋转与投掷臂动力学降低有关，传统上被认为是棒球投手正确投球姿势的一个组成部分。然而，以前对骨盆旋转方式的评估没有考虑到混杂因素，如比赛水平、人体测量特征、球速等，也没有评估足够的样本量。
比较高中生和职业投手基于骨盆旋转方式的动力学和运动学参数。
描述性实验室研究。
高中和职业棒球投手在进行 3 维运动捕捉（480 Hz）评估时投掷 8 到 12 个快球。这些投手根据在足接触时早期（<60°）与晚期（≥60°）骨盆旋转方式，通过年龄、身高、体重、惯用手和球速进行 1:1 的倾向评分匹配。在组间比较了 26 个运动学和 10 个动力学参数。使用线性回归分析足接触时早期和晚期骨盆旋转之间的关系。
对于高中生（ =.243）或职业投手（ =.075），骨盆在足接触时的旋转与球速均无显著相关性。高中生早期旋转者（57.5 ± 14.9 N·m）和晚期旋转者（51.3 ± 14.7 N·m； =.036）以及职业投手早期旋转者（80.1 ± 11.8 N·m）和晚期旋转者（79.0 ± 11.2 N·m； =.663）的肘内翻扭矩无差异。在高中生投手中，在足接触时，步幅长度增加了 2.1%的身高（B = -0.205；β = -0.470； <.001），躯干旋转增加了 4.2°（B = -0.417；β = -0.488； <.001），在足接触时躯干屈曲减少了 4.4°（B = 0.442；β = 0.476； <.001），每增加 10°骨盆旋转。在职业投手中，在足接触时，步幅长度增加了 2.3%的身高（B = -0.229；β = -0.478； <.001），躯干旋转增加了 4.3°（B = -0.431；β = -0.515； <.001），在足接触时躯干屈曲减少了 4.0°（B = 0.404；β = 0.373； <.001），每增加 10°骨盆旋转。
骨盆在足接触时的旋转与两组的几个运动学参数相关，可能会进一步影响动力学链中的力学。与之前的观点相反，在高中和职业棒球投手中，开球或闭球与投掷臂动力学或球速均无显著相关性。
教练和运动员可能会更好地专注于改进其他运动学参数，以提高表现结果和安全投球力学。
