Friedrich-Schiller-Universität, Institut für Sportwissenschaft, Lehrstuhl für Bewegungswissenschaft, Seidelstraße 20, D-07749 Jena, Germany.
Gait Posture. 2011 Mar;33(3):412-7. doi: 10.1016/j.gaitpost.2010.12.014. Epub 2011 Jan 7.
Quiet human stance is a dynamic multi-segment phenomenon. In literature, coupled ankle and hip actions are in the focus and examinations are usually restricted to frequency contributions below 4 Hz. Very few studies point to the knee playing an active role, and just one study gives evidence of higher frequency contributions. In order to investigate the dynamic coupling of all three leg joints in more depth, we revisited an experimental data set on quiet human stance. Since phase synchronisation is a strong indicator of non-linear coupling behind, we used the phase synchronisation index (PSI) to quantify the degree of leg joint coupling as a function of frequency. One main result is that we did not find any synchronisation between ankle and hip across the whole frequency range examined up to 8 Hz. In contrast, there is significant synchronisation between ankle and knee at a couple of frequencies between 1.25 Hz and 8 Hz when looking at the kinematics. Their joint torques rather synchronise below 2 Hz. There is also synchronisation between knee and hip kinematics above 6 Hz, however, only significant at one frequency bin in our data set. From this, we would infer that the multiple mechanical degrees of freedom contributing to quiet human stance should be chosen according to, thus map, physiology. Thereby, the knee is indispensable and bi-articular muscles play a central role in organising quiet human stance. Examining the non-stationarity of phase synchronisations will probably advance the understanding of self-organisation of quiet human stance.
静立姿势是一种动态的多关节现象。在文献中，踝关节和髋关节的耦合作用是研究的焦点，而检查通常仅限于低于 4 Hz 的频率贡献。很少有研究表明膝关节起主动作用，只有一项研究证明了更高频率的贡献。为了更深入地研究三个腿部关节的动态耦合，我们重新研究了关于人类静立姿势的实验数据集。由于相位同步是非线性耦合的一个强有力的指标，我们使用相位同步指数（PSI）来量化腿部关节耦合的程度作为频率的函数。一个主要结果是，我们没有在整个频率范围内（检查至 8 Hz）发现踝关节和髋关节之间存在任何同步。相比之下，当观察运动学时，在 1.25 Hz 到 8 Hz 之间的几个频率上，踝关节和膝关节之间存在显著的同步。它们的关节扭矩在 2 Hz 以下同步。在 6 Hz 以上的膝关节和髋关节运动之间也存在同步，但在我们的数据集仅在一个频率范围内显著。由此，我们推断出，参与静立姿势的多个力学自由度应该根据生理学进行选择，从而映射。因此，膝关节是不可或缺的，双关节肌肉在组织静立姿势中起着核心作用。检查相位同步的非平稳性可能会提高对静立姿势自我组织的理解。
