Yanai Toshimasa, Onuma Kengo, Nagami Tomoyuki
Research Institute of Baseball Science and Faculty of Sport Sciences, Waseda University, Tokorozawa City, Saitama, JAPAN.
Graduate school of Sport Sciences, Waseda University, Tokorozawa City, Saitama, JAPAN.
Med Sci Sports Exerc. 2025 Apr 1;57(4):791-799. doi: 10.1249/MSS.0000000000003614. Epub 2024 Nov 25.
Valgus load opens the medial elbow compartment, causing elongation of the ulnar collateral ligament (UCL) that can eventually lead to attenuation and failure. Ideally, the muscles surrounding the medial aspect of elbow joint should coordinate medial elbow compression to prevent the medial elbow compartment from opening and loading the UCL. This study aimed to determine whether baseball pitchers have sufficient elbow varus strength to unload the UCL during pitching.
Using an electromagnetic tracking device, we measured the peak elbow varus moment during pitches (fastball, slider, curveball, and changeup) by 14 professional and 8 collegiate pitchers. Elbow varus strength was measured with an isokinetic dynamometer system while the medial elbow joint space was monitored using ultrasonography. A paired t -test was used to compare the peak varus moment generated during pitching with the varus strength, and the relative intensity of muscular output required to unload the UCL was determined.
Except for curveballs, the muscular varus strength (57.5 ± 9.2 N·m) was not significantly larger ( P = 0.165-0.853) than the peak varus moments during pitching (55.4 ± 13.0 N·m). Ten participants did not have sufficient muscular varus strength to completely unload the UCL from valgus loading when throwing fastballs and other pitch types. The relative intensity of muscular torque output required for stress shielding of the UCL ranged from 89.1% ±21.7% maximum voluntary isometric varus strength (MVIVS) for curveballs to 103.1% ±26.5% MVIVS for fastballs.
Our findings demonstrate that most of the valgus load on the elbow joint during pitching can be counteracted by the muscular varus moment, but valgus loading on the UCL is likely unavoidable in baseball pitching.
外翻负荷会打开内侧肘关节间隙，导致尺侧副韧带（UCL）拉长，最终可能导致韧带松弛和失效。理想情况下，肘关节内侧周围的肌肉应协调内侧肘关节的挤压，以防止内侧肘关节间隙打开并对尺侧副韧带施加负荷。本研究旨在确定棒球投手是否具有足够的肘内翻力量，以便在投球时减轻尺侧副韧带的负荷。
我们使用电磁跟踪设备，测量了14名职业投手和8名大学投手在投球（快球、滑球、曲线球和变速球）过程中的峰值肘内翻力矩。使用等速测力计系统测量肘内翻力量，同时使用超声监测内侧肘关节间隙。采用配对t检验比较投球过程中产生的峰值内翻力矩和内翻力量，并确定减轻尺侧副韧带负荷所需的肌肉输出相对强度。
除曲线球外，肌肉内翻力量（57.5±9.2牛·米）并不显著大于投球过程中的峰值内翻力矩（55.4±13.0牛·米）（P = 0.165 - 0.853）。10名参与者在投快球和其他球路时，没有足够的肌肉内翻力量来完全减轻外翻负荷对尺侧副韧带的压力。尺侧副韧带应力屏蔽所需的肌肉扭矩输出相对强度范围为：曲线球时为最大自主等长内翻力量（MVIVS）的89.1%±21.7%，快球时为103.1%±26.5% MVIVS。
我们的研究结果表明，投球过程中肘关节上的大部分外翻负荷可被肌肉内翻力矩抵消，但在棒球投球中，尺侧副韧带上的外翻负荷可能无法避免。
