PDF(Pubmed)
Abstract：
Introduction: Spaceflight is associated with severe muscular adaptations with substantial inter-individual variability. A Hill-type muscle model is a common method to replicate muscle physiology in musculoskeletal simulations, but little is known about how the underlying parameters should be adjusted to model adaptations to unloading. The aim of this study was to determine how Hill-type muscle model parameters should be adjusted to model disuse muscular adaptations. Methods: Isokinetic dynamometer data were taken from a bed rest campaign and used to perform tracking simulations at two knee extension angular velocities (30°·s-1 and 180°·s-1). The activation and contraction dynamics were solved using an optimal control approach and direct collocation method. A Monte Carlo sampling technique was used to perturb muscle model parameters within physiological boundaries to create a range of theoretical and feasible parameters to model muscle adaptations. Results: Optimal fibre length could not be shortened by more than 67% and 61% for the knee flexors and non-knee muscles, respectively. Discussion: The Hill-type muscle model successfully replicated muscular adaptations due to unloading, and recreated salient features of muscle behaviour associated with spaceflight, such as altered force-length behaviour. Future researchers should carefully adjust the optimal fibre lengths of their muscle-models when trying to model adaptations to unloading, particularly muscles that primarily operate on the ascending and descending limbs of the force-length relationship.
摘要：
简介：太空飞行与严重的肌肉适应有关，个体间差异很大。希尔型肌肉模型是在肌肉骨骼模拟中复制肌肉生理学的常用方法，但是对于如何调整基本参数以适应卸载的模型知之甚少。这项研究的目的是确定如何调整Hill型肌肉模型参数以适应模型废弃的肌肉适应。方法：等速测功机数据取自卧床休息运动，并用于在两个膝盖伸展角速度（30°·s-1和180°·s-1）下进行跟踪模拟。使用最优控制方法和直接搭配方法求解了激活和收缩动力学。使用蒙特卡洛采样技术在生理边界内扰动肌肉模型参数，以创建一系列理论和可行的参数来对肌肉适应进行建模。结果：膝屈肌和非膝肌的最佳纤维长度不能缩短超过67%和61%，分别。讨论：希尔型肌肉模型成功复制了由于卸载而引起的肌肉适应，并重现了与太空飞行相关的肌肉行为的显着特征，例如改变力长行为。未来的研究人员在尝试对卸载进行建模时，应仔细调整其肌肉模型的最佳纤维长度，特别是主要作用在力长关系的上升和下降肢体上的肌肉。
