Afschrift Maarten, Jonkers Ilse, De Schutter Joris, De Groote Friedl
Human Movement Biomechanics Research Group, Department of Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium; and
Human Movement Biomechanics Research Group, Department of Kinesiology, Katholieke Universiteit Leuven, Leuven, Belgium; and.
J Neurophysiol. 2016 Oct 1;116(4):1937-1945. doi: 10.1152/jn.00127.2016. Epub 2016 Aug 3.
Experimental studies have shown that a continuum of ankle and hip strategies is used to restore posture following an external perturbation. Postural responses can be modeled by feedback control with feedback gains that optimize a specific objective. On the one hand, feedback gains that minimize effort have been used to predict muscle activity during perturbed standing. On the other hand, hip and ankle strategies have been predicted by minimizing postural instability and deviation from upright posture. It remains unclear, however, whether and how effort minimization influences the selection of a specific postural response. We hypothesize that the relative importance of minimizing mechanical work vs. postural instability influences the strategy used to restore upright posture. This hypothesis was investigated based on experiments and predictive simulations of the postural response following a backward support surface translation. Peak hip flexion angle was significantly correlated with three experimentally determined measures of effort, i.e., mechanical work, mean muscle activity and metabolic energy. Furthermore, a continuum of ankle and hip strategies was predicted in simulation when changing the relative importance of minimizing mechanical work and postural instability, with increased weighting of mechanical work resulting in an ankle strategy. In conclusion, the combination of experimental measurements and predictive simulations of the postural response to a backward support surface translation showed that the trade-off between effort and postural instability minimization can explain the selection of a specific postural response in the continuum of potential ankle and hip strategies.
实验研究表明，在受到外部扰动后，会采用一系列连续的踝关节和髋关节策略来恢复姿势。姿势反应可以通过具有优化特定目标的反馈增益的反馈控制来建模。一方面，已使用使努力最小化的反馈增益来预测受扰站立期间的肌肉活动。另一方面，通过最小化姿势不稳定性和与直立姿势的偏差来预测髋关节和踝关节策略。然而，努力最小化是否以及如何影响特定姿势反应的选择仍不清楚。我们假设，最小化机械功与姿势不稳定性的相对重要性会影响用于恢复直立姿势的策略。基于对向后支撑面平移后姿势反应的实验和预测模拟，对这一假设进行了研究。髋关节最大屈曲角度与三个通过实验确定的努力指标显著相关，即机械功、平均肌肉活动和代谢能量。此外，在模拟中，当改变最小化机械功和姿势不稳定性的相对重要性时，预测出了一系列连续的踝关节和髋关节策略，机械功权重增加会导致采用踝关节策略。总之，对向后支撑面平移的姿势反应进行实验测量和预测模拟相结合的结果表明，努力与姿势不稳定性最小化之间的权衡可以解释在潜在的踝关节和髋关节策略连续体中特定姿势反应的选择。
