Dept. of Sport Rehabilitation, Division of PT & OT Sciences, Graduate School of Health Sciences, Hiroshima University, Kasumi1-2-3 , Minami-ku, Hiroshima, Japan.
J Sports Sci Med. 2008 Mar 1;7(1):47-53. eCollection 2008.
The amount of stress imposed on shoulder and elbow appears to be directly correlated with the degree of maximum shoulder external rotation (MER) during throwing motions. Therefore, identifying risk factors contributing to the increase of MER angle may help to decrease the throwing injuries occurrence in baseball players. The purpose of the present study was to demonstrate the correlation between MER and the kinematic variables at stride foot contact (SFC) during the early cocking phase, the passive range of motion (ROM), and the shoulder strength. The subjects were 40 high school baseball players. Each subject carried out five throwing tasks with his maximum effort. A three-dimensional analysis was performed to obtain the MER, and the shoulder angles of external rotation (ER), extension and abduction at SFC in the early cocking phase. The ROM and muscle strength of the shoulder ER and internal rotation (IR) were also measured. Significant moderate linear correlations were found between the MER and the ER (r = -0.32, p = 0.04) at SFC, extension angle ( r= 0.35, p = 0.03) at SFC, IR strength (r = -0.30, p = 0.04) and passive ROM of ER (r = 0.46, p = 0.01). The shoulder IR and extension angles at SFC may determine the degree of the MER angle. Furthermore, weak IR muscle strength and excessive ROM of ER might be risk factors for shoulder and elbow injuries. The finding will enable us to establish better prevention and rehabilitation strategies for throwing injuries in baseball players. Key pointsIt has been reported that the amount of stress imposed on shoulder and elbow joints is correlated with the degree of maximum shoulder external rotation angle (MER) during throwing. Therefore, controlling MER within a normal range plays a key role in the prevention for throwing-related injuries in baseball players.Physical and biomechanical factors related to the degree of MER must be addressed to advance the current prevention and rehabilitation strategies for the shoulder and elbow injuries.The current finding demonstrated that there was a significant moderate leaner correlation between shoulder internal rotation angle at the initial foot contact in the early cocking phase and MER.
施加在肩部和肘部的压力似乎与投掷动作中最大肩部外旋角度（MER）的程度直接相关。因此，确定导致 MER 角度增加的危险因素可能有助于减少棒球运动员的投掷伤发生率。本研究的目的是证明在早期预挥阶段的初始触地脚（SFC）处，MER 与运动学变量之间的相关性，这些运动学变量包括肩部外旋（ER）的被动活动范围（ROM）和肩部力量。受试者为 40 名高中棒球运动员。每位受试者都以最大努力进行了五次投掷任务。进行了三维分析以获得 MER，以及在早期预挥阶段的 SFC 处的肩部 ER、伸展和外展角度。还测量了肩部 ER 和内旋（IR）的 ROM 和肌肉力量。在 SFC 处的 ER（r=-0.32，p=0.04）、伸展角度（r=0.35，p=0.03）、IR 力量（r=-0.30，p=0.04）和 ER 的被动 ROM 之间发现了显著的中度线性相关性（r=0.46，p=0.01）。SFC 处的肩部 IR 和伸展角度可能决定了 MER 角度的程度。此外，IR 肌肉力量较弱和 ER 的 ROM 过大可能是肩部和肘部受伤的危险因素。这一发现将使我们能够为棒球运动员的投掷伤建立更好的预防和康复策略。关键点已有报道称，施加在肩部和肘部关节上的压力与投掷过程中最大肩部外旋角度（MER）的程度有关。因此，将 MER 控制在正常范围内是预防棒球运动员投掷伤的关键。必须解决与 MER 程度相关的物理和生物力学因素，以推进当前针对肩部和肘部受伤的预防和康复策略。目前的研究结果表明，在早期预挥阶段的初始触地脚处肩部内旋角度与 MER 之间存在显著的中度线性相关性。
