Department of Integrative Physiology, University of Colorado Boulder, Campus Box 354, Boulder, CO, 80309, USA.
Center for Orthopedic Biomechanics, Ritchie School of Mechanical Engineering and Computer Science, University of Denver, 2155 E. Wesley Ave., Denver, CO, 80210, USA.
Exp Brain Res. 2020 Feb;238(2):487-497. doi: 10.1007/s00221-019-05719-4. Epub 2020 Jan 20.
Upright standing involves small displacements of the center of mass about the base of support. These displacements are often quantified by measuring various kinematic features of the center-of-pressure trajectory. The plantar flexors have often been identified as the key muscles for the control of these displacements; however, studies have suggested that the hip abductor and adductors may also be important. The purpose of our study was to determine the association between the force capabilities of selected leg muscles and sway-area rate across four balance conditions in young (25 ± 4 years; 12/19 women) and older adults (71 ± 5 years; 5/19 women). Due to the marked overlap in sway-area rate between the two age groups, the data were collapsed, and individuals were assigned to groups of low- and high-sway area rates based on a k-medoid cluster analysis. The number of participants assigned to each group varied across balance conditions and a subset of older adults was always included in the low-sway group for each balance condition. The most consistent explanatory variable for the variance in sway-area rate was force control of the hip abductors and ankle dorsiflexors as indicated by the magnitude of the normalized force fluctuations (force steadiness) during a submaximal isometric contraction. The explanatory power of the regression models varied across conditions, thereby identifying specific balance conditions that should be examined further in future studies of postural control.
直立站立涉及质心围绕支撑基础的小位移。这些位移通常通过测量压力中心轨迹的各种运动学特征来量化。足底屈肌通常被认为是控制这些位移的关键肌肉；然而，研究表明，髋关节外展肌和内收肌也可能很重要。我们的研究目的是确定在四个平衡条件下，选定腿部肌肉的力量能力与摆动面积率之间的关系，研究对象为年轻（25 ± 4 岁；12/19 名女性）和老年人（71 ± 5 岁；5/19 名女性）。由于两个年龄组的摆动面积率有明显的重叠，因此将数据合并，并根据 k-medoid 聚类分析将个体分配到低摆动面积率和高摆动面积率组。在每个平衡条件下，分配给每个组的参与者数量都有所不同，并且对于每个平衡条件，总是有一部分老年人被分配到低摆动组。摆动面积率方差的最一致解释变量是髋关节外展肌和踝关节背屈肌的力控制，这由亚最大等长收缩期间归一化力波动（力稳定性）的大小表示。回归模型的解释能力因条件而异，从而确定了在未来的姿势控制研究中应进一步研究的特定平衡条件。
