Ashtiani Mohammed N, Azghani Mahmood-Reza, Parnianpour Mohamad
1 Faculty of Biomedical Engineering, Sahand University of Technology, Tabriz, Iran.
2 Department of Physiotherapy, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran.
Proc Inst Mech Eng H. 2018 Dec;232(12):1255-1260. doi: 10.1177/0954411918811858. Epub 2018 Nov 20.
The static initial postures of standing before applying perturbations may affect the maintenance of postural balance. The goal of this article was to find the stable set of postures and then determine the roles of joint mechanisms. The set of posture was defined in a biomechanical model based on three joint angles of the lower limbs. Optimized inverse dynamics method was used to solve for muscle forces in a precise model of the human musculoskeletal system posed in 4096 static sets of posture using AnyBody software. Results showed that the overall body muscular activity in standing is reduced by knee flexion. Moderate knee angles between 20° and 60° provided safer postures against possible perturbations because of higher collaboration levels of the joint mechanisms. About 36% of the overall postural infeasibilities were attributed to the inability of the ankle muscles to more sustain the exerted loads. Although the roles of the joint mechanisms were closely dependent on the postures, there was no direct relation between the joint kinematics and activation levels of their supporting muscles. Lower extremity muscle groups collaborate to maintain the balance in a considerable number of static postures.
施加扰动前站立的静态初始姿势可能会影响姿势平衡的维持。本文的目的是找到稳定的姿势集，然后确定关节机制的作用。姿势集是在基于下肢三个关节角度的生物力学模型中定义的。使用优化的逆动力学方法，利用AnyBody软件在4096组静态姿势的人体肌肉骨骼系统精确模型中求解肌肉力。结果表明，站立时膝关节屈曲会降低全身肌肉活动。20°至60°之间的适度膝关节角度由于关节机制的协作水平较高，提供了更安全的姿势以抵御可能的扰动。约36%的整体姿势不可行性归因于踝关节肌肉无法更多地承受施加的负荷。尽管关节机制的作用紧密依赖于姿势，但关节运动学与其支撑肌肉的激活水平之间没有直接关系。下肢肌肉群在相当多的静态姿势中协同维持平衡。
