Reciprocal angular acceleration of the ankle and hip joints during quiet standing in humans

Abstract

Human quiet standing is often modeled as a single inverted pendulum rotating around the ankle joint, under the assumption that movement around the hip joint is quite small. However, several recent studies have shown that movement around the hip joint can play a significant role in the efficient maintenance of the center of body mass (COM) above the support area. The aim of this study was to investigate how coordination between the hip and ankle joints is controlled during human quiet standing. Subjects stood quietly for 30 s with their eyes either opened (EO) or closed (EC), and we measured subtle angular displacements around the ankle (thetaa) and hip (thetah) joints using three highly sensitive CCD laser displacement sensors. Reliable data were obtained for both angular displacement and angular velocity (the first derivative of the angular displacement). Further, measurement error was not predominant, even among the angular acceleration data, which were obtained by taking the second derivative of the angular displacement. The angular displacement, velocity, and acceleration of the hip were found to be significantly greater (P<0.001) than those of the ankle, confirming that hip-joint motion cannot be ignored, even during quiet standing. We also found that a consistent reciprocal relationship exists between the angular accelerations of the hip and ankle joints, namely positive or negative angular acceleration of ankle joint is compensated for by oppositely directed angular acceleration of the hip joint. Principal component analysis revealed that this relationship can be expressed as: thetah=gammathetaa with gamma=-3.15+/-1.24 and gamma=-3.12+/-1.46 (mean +/-SD) for EO and EC, respectively, where theta is the angular acceleration. There was no significant difference in the values of y for EO and EC, and these values were in agreement with the theoretical value calculated assuming the acceleration of COM was zero. On the other hand, such a consistent relationship was never observed for angular displacement itself. These results suggest that the angular motions around the hip and ankle joints are not to keep the COM at a constant position, but rather to minimize acceleration of the COM.

Organization of postural responses following a rotational support surface perturbation, after TKA: Sagittal plane rotations

“…Similar to responses following support surface translations, patients with vestibular loss or proprioceptive loss show changes in muscle activity onset latency and amplitude [12,13]. The human postural control literature has focused on the roles of the ankle and hip joints during quiet standing, and in response to postural perturbations [8,[14][15][16]. Only recently has the knee joint been examined in postural control and balance recovery.…”

The influence of artificially increased hip and trunk stiffness on balance control in man

“…The inverted pendulum model may be valid for a restricted number of movements in a single plane, including those induced by small and slow horizontal support surface translations. Recently, however, this concept has been challenged for motion occurring during quiet stance (Aramaki et al 2001;Loram and Lakie 2002). Indeed, as body motion increases in amplitude and direction from that of quiet standing (Fitzpatrick et al 1992(Fitzpatrick et al , 1994Winter et al 1996Winter et al , 1998Gatev et al 1999;Accorneo et al 1997), to that induced by a support surface perturbation in the pitch plane alone (Cordo and Nashner 1982;Allum et al 1993;Horak et al 1997), and finally to that induced by combined roll and pitch plane perturbations (Moore et al 1988;Maki et al 1994aMaki et al , 1994bHenry et al 1998b;Carpenter et al 1999;Allum et al 2002), the multi-link nature of human postural corrections becomes increasingly prominent.…”

Improvements in Trunk Sway Observed for Stance and Gait Tasks during Recovery from an Acute Unilateral Peripheral Vestibular Deficit

“…To date this has proved difficult to achieve. Inexpensive force transducers in a fixed support surface (static posturography) have been used to provide an indirect measure of body sway for stance tasks alone by assuming, albeit under a debatable assumption, that the body moves as an inverted pendulum [Barin, 1989;Aramaki et al, 2001]. Alternatively, expensive and time-consuming motion analysis systems have been used to calculate angles of body segments for both stance and gait tasks [Krebs and Lockert, 1995;Ferrigno and Pedotti, 1985].…”