Effects of visual perturbation on the gait variability during different locomotion speeds

Temporal and spatial gait variability is relatively small in the healthy walking pattern. Patients with a sensory loss show a pathological increase of gait variability. The purpose of this study was to investigate the influence of artificially disturbed visual locomotion control on the gait variability during different locomotion speeds. Nine healthy subjects (31.0±8.4 years, 2 females) participated in the study. For each subject the walking pattern was recorded while walking under normal conditions and while walking under visual perturbation (VP). Therefor, subjects were artificially blinded with light-impenetrable eyeglasses. For each condition, subjects had to walk in five different locomotion speeds on a pressure-sensitive treadmill system (Zebris®).

The magnitude of the fluctuations of stride time (ST), stride length (SL) and base width (BW) was analyzed by calculating the coefficient of variation (CV). For normal walking mode the gait variability in the longitudinal plane (i.e. ST and SL) and the lateral plane (i.e. BW) was in the normal range and did not show any significant speed effects. Under VP, longitudinal gait parameters showed significant speed effects and were significantly increased (p<0.001) most pronounced for slow locomotion speeds. Lateral gait variability did not show significant speed effects but was significantly increased (p<0.05). VP has a direct effect on the magnitude of stride-to-stride fluctuations in the walking pattern. This impact is differentially pronounced for different walking speeds as well as the variability in the longitudinal and lateral walking plane. These results are highly comparable to the effects of a vestibular loss on the gait variability in patients with a bilateral vestibular failure. Taken together, the speed dependent impacts of sensory perturbation on the gait variability support the hypothesis of a speed dependent sensory locomotion control.

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