Is slow walking more stable?

Several efforts have been made to study gait stability using measures derived from nonlinear time-series analysis. The maximum finite time Lyapunov exponent (

The effects of arm swing on human gait stability

Arm swing during human gait has been shown to reduce both angular momentum about the vertical and energy expenditure, and has been hypothesized to enhance gait stability. To examine this hypothesis, we studied the effect of arm swing on the local and global stability of steady-state gait, as well as the ability to perform adequate recovery actions following a perturbation. Trunk kinematics of 11 male subjects was measured in treadmill walking with normal and with restricted arm swing. In half of the trials, gait was perturbed by a position-controlled forward pull to the trunk. We constructed state spaces using data recorded from the unperturbed steady-state walking trials, and quantified local gait stability by calculating maximum Lyapunov exponents. In addition, we analyzed perturbation forces, the distance from the unperturbed gait pattern, and the return toward the normal gait pattern following an external perturbation. Walking without arm swing led to a non-significantly lower Lyapunov exponent (P0.06), significantly higher perturbation forces (P<0.05), and significantly slower movements away from the attractor (P<0.01). These results suggest that gait without arm swing is characterized by similar local stability to gait with arm swing and a higher perturbation resistance. However, return towards the normal gait pattern was significantly slower (P<0.05) when walking with restricted arms, suggesting that the arms play an important role in the recovery from a perturbation. Collectively, the results suggest that arm swing as such does not enhance gait stability, but rather that recovery movements of the arms contribute to the overall stability of human gait. © 2010. Published by The Company of Biologists Ltd

Mechanical Perturbations of the Walking Surface Reveal Unaltered Axial Trunk Stiffness in Chronic Low Back Pain Patients.

INTRODUCTION:Patients with chronic low back pain (CLBP) often demonstrate altered timing of thorax rotations in the transverse plane during gait. Increased axial trunk stiffness has been claimed to cause this movement pattern. OBJECTIVES:The objective of this study was to assess whether axial trunk stiffness is increased in gait in CLBP patients. METHODS:15 CLBP patients and 15 healthy controls walked on a treadmill that imposed rotational perturbations in the transverse plane. The effect of these perturbations on transverse pelvis, thorax and trunk (thorax relative to pelvis) rotations was evaluated in terms of residual rotations, i.e., the deviation of these movements from the unperturbed patterns. In view of the heterogeneity of the CLBP group, we additionally performed a subgroup comparison between seven patients and seven controls with maximal between-group contrast for timing of thorax rotations. RESULTS:Rotations of the walking surface had a clear effect on transverse pelvis, thorax and trunk rotations in all groups. No significant between-group differences on residual transverse pelvis, thorax and trunk rotations were observed. CONCLUSION:Axial trunk stiffness in gait does not appear to be increased in CLBP. Altered timing of thorax rotations in CLBP does not seem to be a result of increased axial trunk stiffness