Background: Elbow flexion at stagnant time points of the pitch has been associated with increased elbow varus torque (EVT) and elbow injury history. Purpose: To determine how elbow flexion angle throughout the pitch (excursion) between individual pitchers and a cohort of pitchers influences throwing arm kinetics in high school (HS) and professional (PRO) pitchers. Study Design: Descriptive laboratory study. Methods: HS (n = 59) and PRO (n = 288) pitchers were instructed to throw 8 to 12 fastball pitches evaluated with 3-dimensional motion capture system (480 Hz). Linear regression models were developed to examine the association between elbow flexion excursion with ball velocity and throwing arm kinetics. An intrapitcher analysis utilizing a linear mixed model was also used, introducing pitchers as a random effect. Results: The mean elbow flexion excursion was significantly greater for HS (70° ± 22°) compared with PRO (63° ± 21°) pitchers ( P < .001), while the mean normalized EVT was significantly less for HS pitchers (3.9% ± 0.7% vs 4.8% ± 0.8% body weight [BW] × body height; P < .001). For every 1 SD increase in elbow excursion, ball velocity increased by 0.8 to 1.0 m/s (approximately 2 mph) for intra- and interanalyses ( P max = 0.006; β = 0.31-0.39) for HS pitchers, while it increased by only 0.2 to 0.4 m/s (<1 mph) for PRO pitchers ( P max = 0.016; β = 0.10-0.17). EVT increased by 0.34 to 0.40 SD for every 1 SD increase in elbow excursion for intra- and interanalyses for HS pitchers and by 0.13 to 0.22 SD for PRO pitchers. Elbow medial force increased by 1.9% to 2.3% BW for every 1 SD increase in elbow excursion for intra- and interanalyses of HS pitchers (β = 0.35-0.44) and by 1.4% to 1.7% BW increase for PRO pitchers (β = 0.23-0.27). Conclusion: PRO pitchers have decreased elbow flexion excursion compared with HS pitchers. This may be an advantageous mechanism by which to minimize throwing arm kinetics, including EVT and elbow medial force, supported by both intra- and interpitcher analyses. Ball velocity benefits with increased elbow excursion were marginal for both cohorts. Clinical Relevance: In support of previous literature suggesting that increased elbow flexion at later portions of the pitch is associated with increased EVT and injury history, this study further substantiates that this may be deleterious kinematics to baseball pitchers.

中文翻译：

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肘部屈曲偏移：高中和职业棒球投手的投掷臂内和投掷臂间动力学评估


背景：在球场停滞的时间点肘部屈曲与肘部内翻扭矩 （EVT） 和肘部受伤史增加有关。目的：确定单个投手和一组投手之间在整个投球（偏移）过程中的肘部屈曲角度如何影响高中 （HS） 和专业 （PRO） 投手的投掷臂动力学。研究设计： 描述性实验室研究。方法：指示 HS （n = 59） 和 PRO （n = 288） 投手投出 8 到 12 个快球投球，并使用 3 维动作捕捉系统 （480 Hz） 进行评估。开发了线性回归模型来检查肘部屈曲偏移与球速和投掷臂动力学之间的关联。还使用了利用线性混合模型的投手内部分析，将投手作为随机效应引入。结果： 与 PRO （70° ± 22°） 投手 （63° ± 21°） 投手 （P < .001） 相比，HS 投手的平均标准化 EVT 显着较小 （3.9% ± 0.7% vs 4.8% ± 0.8% 体重 [BW] ×身高;P < .001）。肘部偏移每增加 1 个标准差，HS 投手的内部和内部分析球速增加 0.8 至 1.0 米/秒（约 2 英里/小时）（Pmax = 0.006;β = 0.31-0.39），而专业投手仅增加 0.2 至 0.4 米/秒（<1 英里/小时）（Pmax = 0.016;β = 0.10-0.17）。HS 投手的内部和内部分析的肘部偏移每增加 0.34 至 0.40 SD，EVT 就会增加 0.34 至 0.40 SD，PRO 投手的肘部偏移增加 0.13 至 0.22 SD。 对于 HS 投手的内部和内部分析，肘部内侧力每增加 1 个标准差，肘部内侧力就会增加 2.3% 至 2.3% BW （β = 0.35-0.44），PRO 投手的肘部内侧力增加 1.4% 至 1.7% BW （β = 0.23-0.27）。结论：与 HS 投手相比，PRO 投手的肘关节屈曲偏移减少。这可能是一种有利的机制，通过该机制可以最大限度地减少投掷臂动力学，包括 EVT 和肘部内侧力，并得到投球手内和投手间分析的支持。对于两个队列，肘部偏移增加的球速益处都是微不足道的。临床相关性：为了支持先前的文献表明，在球场后期增加的肘部屈曲与 EVT 和受伤史的增加有关，这项研究进一步证实这可能对棒球投手有害的运动学。