Department of Orthopaedics, Leiden University Medical Center, Leiden, the Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Leiden, the Netherlands.
Department of Orthopaedics, Leiden University Medical Center, Leiden, the Netherlands; Laboratory for Kinematics and Neuromechanics, Leiden University Medical Center, Leiden, the Netherlands.
J Electromyogr Kinesiol. 2019 Dec;49:102351. doi: 10.1016/j.jelekin.2019.102351. Epub 2019 Aug 21.
Middle-aged individuals cocontract with adductor muscles during abduction. This may be crucial for counteracting deltoid forces, depressing the humerus and ensuring free passage of subacromial tissues underneath the acromion during abduction. We questioned whether adductor co-contraction is always present, or develops during ageing, in which case it may explain the age-related character of common shoulder conditions such as Subacromial Pain Syndrome. In a cross-sectional analysis with electromyography (EMG), activation patterns of the latissimus dorsi, teres major, pectoralis major and deltoid muscle were assessed during isometric force tasks in 60 asymptomatic individuals between 21 and 60 years old. Cocontraction was expressed as the degree of antagonistic activation relative to the same muscle's degree of agonistic activation, resulting in an activation ratio between -1 and 1, where lower values indicate more cocontraction. Using linear regression analyses, we found age-related decreases in the activation ratio of the latissimus dorsi (regression estimate: -0.004, 95% CI: -0.007 to 0.0, p-value: 0.042) and teres major (regression estimate: -0.013, 95% CI: -0.019 to -0.008, p-value: <0.001). In contrast to young individuals, middle-aged individuals showed a high degree of adductor cocontraction during abduction. This may indicate that during ageing, alterations in activation patterns are required for preserving pain-free shoulder function.
中年个体在进行外展时会协同收缩内收肌。这对于对抗三角肌的力量、压低肱骨并确保在三角肌下间隙组织在外展时顺利通过肩峰下间隙可能至关重要。我们想知道内收肌的协同收缩是否总是存在，或者是否在衰老过程中发展，如果是这样，它可能可以解释肩峰下疼痛综合征等常见肩部疾病的年龄相关性特征。在一项使用肌电图（EMG）的横断面分析中，我们评估了 60 名无症状个体在 21 至 60 岁之间进行等长力任务时，背阔肌、大圆肌、胸大肌和三角肌的肌肉激活模式。协同收缩用拮抗肌激活相对于同一肌肉的主动肌激活的程度来表示，结果得出一个激活比，范围在-1 到 1 之间，其中较低的值表示协同收缩程度越高。使用线性回归分析，我们发现背阔肌（回归估计值：-0.004，95%置信区间：-0.007 至 0.0，p 值：0.042）和大圆肌（回归估计值：-0.013，95%置信区间：-0.019 至 -0.008，p 值：<0.001）的激活比与年龄相关的降低。与年轻人相比，中年人在进行外展时会表现出高度的内收肌协同收缩。这可能表明，在衰老过程中，为了保持无痛的肩部功能，需要改变激活模式。
