caa a22 4500 445811919 CHVBK 20180317145214.0 cr unu---uuuuu 170323e20110301xx s 000 0 eng 10.1007/s00419-010-0414-y doi (NATIONALLICENCE)springer-10.1007/s00419-010-0414-y Watching quiet human stance to shake off its straitjacket [Elektronische Daten] [Michael Günther, Otto Müller, Reinhard Blickhan] The single-inverted pendulum (SIP) model is still the paradigm describing dynamics and control of quiet human stance in the sagittal plane. We used two methods to verify this paradigm. First, in an experimental approach we acquired kinematic data of both legs of ten subjects at high spatial resolution while quietly standing on two force platforms. We calculated all leg joint angles, the belonging joint torques using inverse dynamics and estimates of joint stiffnesses. Some linear correlations and regressions of both local (joint) and global (COM, COP: centre of mass respectively pressure) variables predicted by the SIP model were investigated. All three verification criteria applied to mean values extracted from experimental data revealed that the SIP is not a valid model for quiet human stance. As a second method, we used computer synthesis to demonstrate that a double-inverted pendulum (DIP) model enters a stable attractor when just the "hip” joint torque is regulated, whereas no torque is applied to the "ankle” joint. Here, angle and torque fluctuations are necessary because such a DIP strategy is of inevitable dynamic character. The two predicted eigenfrequencies of this regulated DIP model approximate the upper and lower limits of the main part of measured power spectra of quiet human stance. We suggest this dynamic necessity to be representative of the biological constraints under which a mechanically unstable inverted multi-segment chain must be stabilised. Springer-Verlag, 2010 Biomechanical model nationallicence Posture control nationallicence Inverse dynamics nationallicence Inverted pendulum nationallicence Double pendulum nationallicence (Time) sequence : An array of values of measured variables (positional or force components) sampled discretely versus time nationallicence Trial : Acquisition of one (consistent and synchronised) data set containing all (time) sequences of the measured variables nationallicence N : Number of trials (60) nationallicence f s : Sampling frequency of the kinematic data (115.5Hz) nationallicence f h : High-pass cutoff-frequency of the kinetic data ($${\frac{1}{8}\,{\rm Hz}}$$) nationallicence SIP : (Single)-inverted pendulum nationallicence DIP : Double-inverted pendulum nationallicence Segment : A fraction of whole body mass located between joints (right and left foot, shank, thigh plus HAT) nationallicence HAT : Segment including head, arms, and trunk nationallicence COM : Centre of mass nationallicence COP : Centre of pressure nationallicence HAT-COM : COM of the HAT-segment nationallicence GRF : Ground reaction force nationallicence DOF : Degree of freedom nationallicence s.d. : Standard deviation nationallicence min : Minimum nationallicence max : Maximum nationallicence $${\mathcal{M}}$$ : Body mass nationallicence g : Gravitational acceleration nationallicence h : Distance between ankle joint and COM nationallicence Θcom : Moment of inertia for the body rotating around its COM ($${\approx \frac{1}{5}\cdot \mathcal{M}\cdot h^{2}}$$) nationallicence Θ : Body moment of inertia for rotation around ankle joint ($${=\mathcal{M}\cdot h^{2} + \Theta_{\rm com}}$$) nationallicence K : Rotational "ankle stiffness” of the SIP model (i.e., unit: Nm/rad) nationallicence K ankle : Sum of real, measured right and left ankle stiffnesses nationallicence K crit : Critical "ankle stiffness” ($${= \mathcal{M}\cdot g\cdot h}$$) nationallicence K eff : Effective stiffness for the SIP model (= K − K crit) nationallicence ω : Angular eigenfrequency of the SIP model $${\left(=\sqrt{\frac{K - K_{\rm crit}}{\Theta}}\, = \,\sqrt{\frac{K_{\rm eff}}{\Theta}}\right)}$$ nationallicence ν : Eigenfrequency of the SIP model $${\left(= \frac{\omega}{2 \pi}\right)}$$ nationallicence $${\tau_{\rm acc}^{2}}$$ : $${= \frac{\Theta}{K_{\rm crit}}\, = \,\left(\frac{K}{K_{\rm crit}} - 1\right) \cdot \frac{1}{\omega^{2}}\, = \,\frac{K_{\rm eff}}{K_{\rm crit}}\cdot \frac{1}{\omega^{2}}}$$ nationallicence Günther Michael Orthopädische Klink, Biomechaniklabor, Eberhard-Karls-Universität, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany aut Müller Otto Orthopädische Klink, Biomechaniklabor, Eberhard-Karls-Universität, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany aut Blickhan Reinhard Institut für Sportwissenschaft, Lehrstuhl für Bewegungswissenschaft, Friedrich-Schiller-Universität, Seidelstraße 20, 07749, Jena, Germany aut Archive of Applied Mechanics Springer-Verlag 81/3(2011-03-01), 283-302 0939-1533 81:3<283 2011 81 419 https://doi.org/10.1007/s00419-010-0414-y text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00419-010-0414-y text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Günther Michael Orthopädische Klink, Biomechaniklabor, Eberhard-Karls-Universität, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany aut NATIONALLICENCE 700 1- Müller Otto Orthopädische Klink, Biomechaniklabor, Eberhard-Karls-Universität, Hoppe-Seyler-Straße 3, 72076, Tübingen, Germany aut NATIONALLICENCE 700 1- Blickhan Reinhard Institut für Sportwissenschaft, Lehrstuhl für Bewegungswissenschaft, Friedrich-Schiller-Universität, Seidelstraße 20, 07749, Jena, Germany aut NATIONALLICENCE 773 0- Archive of Applied Mechanics Springer-Verlag 81/3(2011-03-01), 283-302 0939-1533 81:3<283 2011 81 419 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer