Neuromotor Control and Rehabilitation Laboratory, School of Kinesiology, Louisiana State University, Baton Rouge, LA, USA.
Biomechanics Laboratory, School of Sport and Exercise Science, University of Northern Colorado, Greeley, CO, USA.
Exp Brain Res. 2020 May;238(5):1203-1218. doi: 10.1007/s00221-020-05800-3. Epub 2020 Apr 4.
Transporting an object during locomotion is one of the most common activities humans perform. Previous studies have shown that continuous and predictive control of grip force, along with the inertial load force of the object, is required to complete this task successfully. Another possible CNS strategy to ensure the dynamic stability of the upper limb is to modify the apparent stiffness and damping via altered muscle activation patterns. In this study, the term damping was used to describe a reduction in upper limb vertical oscillation amplitude to maintain the orientation of the hand-held object. The goal of this study was to identify the neuromuscular strategy for controlling the upper limb during object transport while walking. Three-dimensional kinematic and surface electromyography (EMG) data were recorded from eight, right-handed, healthy young adults who were instructed to walk on a treadmill while carrying an object in their dominant/non-dominant hand, with dominant/non-dominant arm positioning but without an object, and without any object or instructed arm-positioning. EMG recordings from the dominant and non-dominant arms were decomposed separately into underlying muscle synergies using non-negative matrix factorization (NNMF). Results revealed that the dominant arm showed higher damping compared to the non-dominant arm. All muscles showed higher mean levels of activation during object transport except for posterior deltoid (PD), with activation peaks occurring around or slightly before heel contact. The muscle synergy analysis revealed an anticipatory stabilization of the shoulder and elbow joints through a proximal-to-distal muscle activation pattern. These activations appear to play an essential role in maintaining the stability of the carried object in addition to the adjustment of grip force against the perturbations caused by heel contact during walking.
在运动过程中搬运物体是人类最常见的活动之一。先前的研究表明，为了成功完成此任务，需要对握力进行连续且可预测的控制，并与物体的惯性负载力相配合。为确保上肢的动态稳定性，中枢神经系统可能会采取另一种策略，即通过改变肌肉活动模式来调整表观刚度和阻尼。在本研究中，术语“阻尼”用于描述减少上肢垂直摆动幅度，以保持手持物体的方向。本研究的目的是确定在行走过程中搬运物体时控制上肢的神经肌肉策略。本研究记录了 8 名右手健康年轻成年人的三维运动学和表面肌电图（EMG）数据，他们被要求在手扶跑步机上行走时用惯用/非惯用手拿着物体，用惯用/非惯用臂定位，但不拿物体，也不拿任何物体或指示臂定位。使用非负矩阵分解（NNMF）将主导和非主导手臂的 EMG 记录分别分解为潜在的肌肉协同作用。结果表明，与非主导臂相比，主导臂的阻尼更高。除了后三角肌（PD）外，所有肌肉在搬运物体时的平均激活水平都较高，激活峰值出现在或略早于脚跟接触时。肌肉协同作用分析显示，通过从近端到远端的肌肉激活模式，对肩部和肘部关节进行了预期的稳定化。除了调整握力以应对行走时脚跟接触引起的干扰外，这些激活似乎在维持携带物体的稳定性方面发挥了重要作用。
