Department of Physical Therapy, Akita University Graduate School of Health Sciences, Akita, Japan.
Department of Physical Therapy, Akita University Graduate School of Health Sciences, Akita, Japan.
J Shoulder Elbow Surg. 2024 Dec;33(12):2711-2717. doi: 10.1016/j.jse.2024.05.027. Epub 2024 Jul 14.
The forearm flexor-pronator muscles act as a dynamic elbow stabilizer against elbow valgus load during baseball pitching. The elasticity of these muscles increases with pitching. However, it is unclear whether increased muscle elasticity is associated with greater elbow valgus torque during pitching. This study aimed to determine the relationship between the elasticity of the forearm flexor-pronator muscles and elbow valgus torque during pitching in young baseball pitchers.
We recruited 124 young baseball pitchers aged 9 to 12 years. The exclusion criteria included current pain with pitching, history of surgery on the tested extremity, or injuries on the tested extremity within the past 12 months. Before the examination, participants completed a questionnaire about their age, height, weight, dominant arm, and practice time per week. The strain ratios of flexor carpi ulnaris (FCU), flexor digitorum superficialis (FDS), and pronator teres as the index of muscle elasticity were measured using ultrasound strain elastography. Participants pitched 3 fastballs at a distance of 16 m (52 ft 6 in) with maximum effort while wearing a sensor sleeve that recorded the elbow valgus torque. A multiple linear regression analysis was conducted to examine the association between muscle elasticity and elbow valgus torque, adjusting for age, height, weight, and practice time.
The final analysis included 107 pitchers. After adjusting for covariates, increased strain ratio of the FCU was significantly associated with greater elbow valgus torque (coefficients = 0.038, 95% confidence interval, 0.016-0.059, P < .001). Similarly, increased strain ratio of the FDS was significantly associated with greater elbow valgus torque (coefficients = 0.027, 95% confidence interval, 0.013-0.042, P < .001).
The high elasticities of the FCU and FDS were associated with greater elbow valgus torque during pitching in young baseball pitchers. The high elasticity of these muscles is a protective response and may be necessary for young baseball pitchers with greater elbow valgus torque during pitching. Among young baseball pitchers with greater elbow valgus torque, those who are unable to produce the higher elasticities of these muscles could have greater elbow valgus load during pitching and be at a higher risk for elbow injuries. The measurement of the elasticities of the FCU and FDS may be useful for identifying young baseball pitchers at risk of sustaining elbow injuries.
在棒球投球过程中，前臂屈肌-旋前肌作为肘外翻负荷的动态肘稳定肌。这些肌肉的弹性随着投球而增加。然而，目前尚不清楚肌肉弹性的增加是否与投球时更大的肘外翻扭矩有关。本研究旨在确定年轻棒球投手中，前臂屈肌-旋前肌的弹性与投球时肘外翻扭矩之间的关系。
我们招募了 124 名 9 至 12 岁的年轻棒球投手。排除标准包括投球时出现疼痛、受试肢体接受过手术或过去 12 个月内受试肢体受伤。在检查之前，参与者完成了一份关于年龄、身高、体重、优势手臂和每周练习时间的问卷。使用超声应变弹性成像测量了屈肌腕肌（FCU）、指浅屈肌（FDS）和旋前肌的应变比，作为肌肉弹性的指标。参与者穿着记录肘外翻扭矩的传感器袖套，以最大努力在 16 米（52 英尺 6 英寸）的距离投 3 个快球。进行了多元线性回归分析，以调整年龄、身高、体重和练习时间后，研究肌肉弹性与肘外翻扭矩之间的关系。
最终分析纳入了 107 名投手。调整协变量后，FCU 的应变比增加与肘外翻扭矩增大显著相关（系数=0.038，95%置信区间，0.016-0.059，P<0.001）。同样，FDS 的应变比增加与肘外翻扭矩增大显著相关（系数=0.027，95%置信区间，0.013-0.042，P<0.001）。
FCU 和 FDS 的高弹性与年轻棒球投手中投球时的肘外翻扭矩增大有关。这些肌肉的高弹性是一种保护反应，可能是投球时肘外翻扭矩较大的年轻棒球投手所必需的。在肘外翻扭矩较大的年轻棒球投手中，那些无法产生这些肌肉较高弹性的人，在投球时可能会承受更大的肘外翻负荷，并且肘部受伤的风险更高。FCU 和 FDS 弹性的测量可能有助于识别有发生肘部受伤风险的年轻棒球投手。
