The Dynamics of Postural Sway Cannot Be Captured Using a One-Segment Inverted Pendulum Model: A PCA on Segment Rotations During Unperturbed Stance

Abstract

Pinter IJ, van Swigchem R, van Soest AJ, Rozendaal LA. The dynamics of postural sway cannot be captured using a one-segment inverted pendulum model: a PCA on segment rotations during unperturbed stance. J Neurophysiol 100: 3197-3208, 2008. First published October 1, 2008 doi:10.1152/jn.01312.2007. Research on unperturbed stance is largely based on a one-segment inverted pendulum model. Recently, an increasing number of studies report a contribution of other major joints to postural control. Therefore this study evaluates whether the conclusions originating from the research based on a one-segment model adequately capture postural sway during unperturbed stance. High-pass filtered kinematic data (cutoff frequency 1/30 Hz) obtained over 3 min of unperturbed stance were analyzed in different ways. Variance of joint angles was analyzed. Principalcomponent analysis (PCA) was performed on the variance of lower leg, upper leg, and head-arms-trunk (HAT) angles, as well as on lower leg and COM angle (the orientation of the line from ankle joint to center of mass). It was found that the variance in knee and hip joint angles did not differ from the variance found in the ankle angle. The first PCA component indicated that, generally, the upper leg and HAT segments move in the same direction as the lower leg with a somewhat larger amplitude. The first PCA component relating ankle angle variance and COM angle variance indicated that the ankle joint angle displacement gives a good estimate of the COM angle displacement. The second PCA component on the segment angles partly explains the apparent discrepancy between these findings because this component points to a countermovement of the HAT relative to the ankle joint angle. It is concluded that postural control during unperturbed stance should be analyzed in terms of a multiple inverted pendulum model.

Analysis of the multi-segmental postural movement strategies utilized in bipedal, tandem and one-leg stance as quantified by a principal component decomposition of marker coordinates

“…This suggest that at least in these more complex stances, a simple inverted pendulum model or postural control models only relying on ankle and hip strategy may not adequately represent the multi-faceted structure of human postural sway. Our findings therefore support other studies suggesting that multi-segment postural movement patterns should be considered (Alexandrov et al, 2005;Gunther et al, 2011;Hsu et al, 2007;Park et al, 2012;Pinter et al, 2008). A principal component decomposition of the variability in the posture vectors offers a new approach to study the multi-joint nature of postural stability within subjects or within-subject adaptations to changes in external conditions (Federolf et al, 2012c).…”

“…Some studies imply that combinations of the ankle and hip strategies fully explain the postural control movements (Aristidou et al, 2008;Horak and Nashner, 1986;Kuo and Zajac, 1993;Creath et al, 2005). However, more recent studies suggest that higher order, multisegment movement strategies should also be considered (Alexandrov et al, 2005;Gunther et al, 2011;Hsu et al, 2007;Park et al, 2012;Pinter et al, 2008).…”

Local and global effects of neck muscle vibration during stabilization of upright standing

“…Human erect posture is known to depend on the coordination of numerous biomechanical degrees of freedom (Creath et al 2005;Hsu et al 2007;Pinter et al 2008), based on the integration of vestibular, visual and somatosensory information (Peterka 2002), to stabilize equilibrium and orientation (Horak and MacPherson 1996;Massion 1994). Here, equilibrium refers to the biomechanical requirements of upright stance (stabilizing the center of mass, CoM, within the base of support), while orientation refers to the relative or absolute positions of different body parts such as trunk and head.…”

Event-Based Data Acquisition and Reconstruction—Mathematical Background

“…Early work, for example (Peterka, 2002;Lakie, Caplan, and Loram, 2003;Bottaro et al, 2005;Loram, Maganaris, and Lakie, 2005), was based on a single inverted pendulum, single-input model of the system. More recently, it has been shown (Pinter, van Swigchem, van Soest, and Rozendaal, 2008;Günther, Grimmer, Siebert, and Blickhan, 2009;Blickhan, 2011, 2012) that a multiple segment multiple input model is required to model unconstrained quiet standing and this clearly has implications for the corresponding human control system. Intermittent control has been suggested as the basic algorithm , and and related algorithms have been analysed by Insperger (2006); Stepan and Insperger (2006), Asai et al (2009) and Kowalczyk et al (2012).…”