Differential effects of absent visual feedback control on gait variability during different locomotion speeds

Abstract

Healthy persons exhibit relatively small temporal and spatial gait variability when walking unimpeded. In contrast, patients with a sensory deficit (e.g., polyneuropathy) show an increased gait variability that depends on speed and is associated with an increased fall risk. The purpose of this study was to investigate the role of vision in gait stabilization by determining the effects of withdrawing visual information (eyes closed) on gait variability at different locomotion speeds. Ten healthy subjects (32.2 ± 7.9 years, 5 women) walked on a treadmill for 5-min periods at their preferred walking speed and at 20, 40, 70, and 80 % of maximal walking speed during the conditions of walking with eyes open (EO) and with eyes closed (EC). The coefficient of variation (CV) and fractal dimension (α) of the fluctuations in stride time, stride length, and base width were computed and analyzed. Withdrawing visual information increased the base width CV for all walking velocities (p < 0.001). The effects of absent visual information on CV and α of stride time and stride length were most pronounced during slow locomotion (p < 0.001) and declined during fast walking speeds. The results indicate that visual feedback control is used to stabilize the medio-lateral (i.e., base width) gait parameters at all speed sections. In contrast, sensory feedback control in the fore-aft direction (i.e., stride time and stride length) depends on speed. Sensory feedback contributes most to fore-aft gait stabilization during slow locomotion, whereas passive biomechanical mechanisms and an automated central pattern generation appear to control fast locomotion.

Noise-Enhanced Vestibular Input Improves Dynamic Walking Stability in Healthy Subjects

“…In conformance with previous studies, we observed that deprivation of visual feedback resulted in a decrease of dynamic walking stability during slow walking indicated by increased fore-aft (i.e., stride time and stride length) and medio-lateral (i.e., base of support) stride-to-stride fluctuations, a more variable bilateral phase coordination and a less symmetric gait pattern [3]. It is commonly believed that alterations in walking performance due to a loss of vision cannot be fully compensated by somatosensory and vestibular information [21].…”

“…This observation corresponds to the growing evidence of a speed-dependent role of sensory feedback in locomotion control. Accordingly, the impact of a vestibular, visual or somatosensory loss or perturbation decreases with increasing walking speed [3][4][5]12,24]. Functional imaging studies could further confirm that sensory cortex activity is decreased at faster walking modes [13,32].…”

“…Sensory feedback control during walking is thought to be important for adjusting stride-to-stride trajectories to maintain balance and for smoothing unintended irregularities during motor execution [1,2]. Consequently, an impairment or loss in either of the sensory feedback modalities results in a decreased walking stability accompanied by an increased risk to fall [3][4][5]. The ability to restore sensory function required for a stable walking performance is therefore a desirable treatment option for patients with sensory deficits.…”

“…Head kinematics while walking were measured in order to estimate the magnitude of vestibular inputs during the stimulation trials. The effects of noisy GVS on the walking performance were tested at different walking speeds (i.e., slow, preferred and fast) and it was hypothesized that noisy GVS would predominantly affect slow locomotion modes that are thought to critically rely on sensory feedback control [3,5,12,13]. We further hypothesized that noisy GVS would primarily influence the stride-tostride fluctuation and bilateral coordination characteristics of the walking pattern, which have been shown to be most sensitive to alterations in sensory feedback control [3][4][5] and which are closely linked to dynamic gait stability [14,15].…”

Efeitos de um treino em ambiente virtual sobre o desempenho da marcha e funções cognitivas em idosos saudáveis

“…O controle da marcha em todos os níveis do sistema nervoso depende fortemente das informações sensoriais visuais, vestibulares e proprioceptivas, as quais permitem o seu controle antecipatório 1 e adaptativo 2 (WUEHR et al, 2013).…”