![]() Since the center of body mass (CoM) is located relatively high (in the trunk, ~1 m above the ankles that determines the length of the inverted pendulum) and the base of support is relatively small, the posture is inherently unstable. In quiet standing, CoP oscillates either side of CoM to keep it in a fairly constant position between the two feet (Figure (Figure1C). ![]() In the simplified inverted pendulum model of the upright human posture, the center of body mass (CoM) is the single controlled variable (Winter et al., 2003). We start this review with an influential scheme of the upright posture control based on the idea of the inverted pendulum and the presence of center of pressure (CoP) oscillations, as important measure of postural stability. Various biomechanical and neurophysiological approaches have been used for understanding the mechanisms of balance control (Horak and Macpherson, 1995). Systematic experimental studies of the physiological mechanisms of postural regulation only began a century ago by Sherrington ( 1906, 1915) and were further developed by Magnus (Magnus and de Klein, 1912 Magnus, 1924) and Rademaker ( 1931). From clinical observations, it has long been known that lesions of the central nervous system may result in pronounced changes in posture. The Greek physician Galen of Pergamon was, probably, the first to introduce the concept of muscle tone in his work “De motu musculorum” (Galen, 1549). Life evolved in the presence of gravity and it has long been recognized, from ancient Greece to our days, that posture is maintained by tonic muscle contractions acting against gravity and stabilizing the positions of body segments. Here, we will consider the neuromechanical basis of habitual posture and various concepts that were rather influential in many experimental studies and mathematical models of human posture control. The unique structure, specialization and properties of skeletal muscles should also be taken into account for understanding important peripheral contributors to postural regulation. Disturbances of muscle tone may in turn affect movement performance. While the two levels are inherently interrelated, both neurophysiological and functional considerations point toward distinct neuromuscular underpinnings. However, two different levels have become increasingly apparent in the postural control system, one level sets a distribution of tonic muscle activity (“posture”) and the other is assigned to compensate for internal or external perturbations (“equilibrium”). Equilibrium control is often considered part of postural control. From ancient Greece to nowadays, research on posture control was guided and shaped by many concepts.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |