The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, United States of America.
Wallace H. Coulter Department of Biomedical Engineering, Emory University and Georgia Institute of Technology, Atlanta, Georgia, United States of America.
PLoS One. 2019 Jul 24;14(7):e0219779. doi: 10.1371/journal.pone.0219779. eCollection 2019.
The robustness of motor outputs to muscle dysfunction has been investigated using musculoskeletal modeling, but with conflicting results owing to differences in model complexity and motor tasks. Our objective was to systematically study how the number of kinematic degrees of freedom, and the number of independent muscle actuators alter the robustness of motor output to muscle dysfunction. We took a detailed musculoskeletal model of the human leg and systematically varied the model complexity to create six models with either 3 or 7 kinematic degrees of freedom and either 14, 26, or 43 muscle actuators. We tested the redundancy of each model by quantifying the reduction in sagittal plane feasible force set area when a single muscle was removed. The robustness of feasible force set area to the loss of any single muscle, i.e. general single muscle loss increased with the number of independent muscles and decreased with the number of kinematic degrees of freedom, with the robust area varying from 1% and 52% of the intact feasible force set area. The maximum sensitivity of the feasible force set to the loss of any single muscle varied from 75% to 26% of the intact feasible force set area as the number of muscles increased. Additionally, the ranges of feasible muscle activation for maximum force production were largely unconstrained in many cases, indicating ample musculoskeletal redundancy even for maximal forces. We propose that ratio of muscles to kinematic degrees of freedom can be used as a rule of thumb for estimating musculoskeletal redundancy in both simulated and real biomechanical systems.
肌肉功能障碍对运动输出的稳健性已通过肌肉骨骼建模进行了研究，但由于模型复杂性和运动任务的差异，结果存在冲突。我们的目的是系统研究运动输出对肌肉功能障碍的稳健性如何随运动自由度的数量和独立肌肉执行器的数量而变化。我们采用了人体腿部的详细肌肉骨骼模型，并系统地改变了模型复杂性，创建了六个模型，这些模型的运动自由度分别为 3 个或 7 个，独立肌肉执行器分别为 14 个、26 个或 43 个。我们通过量化单个肌肉切除时矢状面可行力集区域的减少来测试每个模型的冗余性。可行力集区域对任何单个肌肉丧失的稳健性，即一般单个肌肉丧失，随独立肌肉数量的增加而增加，随运动自由度数量的减少而减少，稳健区域变化范围为完整可行力集区域的 1%至 52%。随着肌肉数量的增加，可行力集对任何单个肌肉丧失的最大灵敏度从完整可行力集区域的 75%变化到 26%。此外，在许多情况下，最大力产生的可行肌肉激活范围很大程度上不受限制，这表明即使是最大力也有充足的肌肉骨骼冗余。我们提出，肌肉与运动自由度的比例可以用作估计模拟和真实生物力学系统中肌肉骨骼冗余的经验法则。
