On the Origin of Planar Covariation of Elevation Angles During Human Locomotion

• Published in: Journal of neurophysiology 2008-04, Vol.99 (4), p.1890-1898
• Main Authors: Ivanenko, Y. P, d'Avella, A, Poppele, R. E, Lacquaniti, F
• Format: Article
• Language: English
• Subjects: Adult; Algorithms; Biomechanical Phenomena; Data Interpretation, Statistical; Female; Foot - physiology; Gait - physiology; Hand Strength - physiology; Humans; Infant; Leg - physiology; Locomotion - physiology; Male; Models, Statistical; Principal Component Analysis; Thigh - physiology; Walking - physiology
• ISSN: 0022-3077; 1522-1598
• DOI: 10.1152/jn.01308.2007

1 Department of Neuromotor Physiology, Santa Lucia Foundation, Rome, Italy; 2 Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota; and 3 Department of Neuroscience and 4 Centre of Space Biomedicine, University of Rome Tor Vergata, Rome, Italy Submitted 3 December 2007; accepted in final form 13 February 2008 Leg segment rotations in human walking covary, so that the three-dimensional trajectory of temporal changes in the elevation angles lies close to a plane. Recently the role of central versus biomechanical constraints on the kinematics control of human locomotion has been questioned. Here we show, based on both modeling and experimental data, that the planar law of intersegmental coordination is not a simple consequence of biomechanics. First, the full limb behavior in various locomotion modes (walking on inclined surface, staircase stepping, air-stepping, crouched walking, hopping) can be expressed as 2 degrees of freedom planar motion even though the orientation of the plane and pairwise segment angle correlations may differ substantially. Second, planar covariation is not an inevitable outcome of any locomotor movement. It can be systematically violated in some conditions (e.g., when stooping and grasping an object on the floor during walking or in toddlers at the onset of independent walking) or transferred into a simple linear relationship in others (e.g., during stepping in place). Finally, all three major limb segments contribute importantly to planar covariation and its characteristics resulting in a certain endpoint trajectory defined by the limb axis length and orientation. Recent advances in the neural control of movement support the hypothesis about central representation of kinematics components. Address for reprint requests and other correspondence: Y. P. Ivanenko, Dept. of Neuromotor Physiology, Scientific Institute Foundation Santa Lucia, 306 via Ardeatina, 00179 Rome, Italy (E-mail: y.ivanenko{at}hsantalucia.it )