Abstract
The visual system is fundamental for the control of gait stability. Visual deprivation or impairment can deteriorate walking stability in adults; however, in daily life, adults are exposed to different light intensities rather than visual deprivation. The objective of this study was to investigate gait stability in young adults exposed to different visual conditions. Ten adults without visual problems participated in the study. The subjects walked at two speeds (self-selected and 30% faster) under four visual conditions: normal vision and using three different masks covered with automotive film to reduce the passage of light to the eye (50% > 20% > 5% - lowest light passage). Stability parameters (margin of stability - MOS, center of mass separation - COMSEP, and time-to-contact - TtC) obtained by analysis of the COM displacement relative to the base of support, and spatiotemporal parameters (step length, gait velocity, and support time) were assessed. The different visual conditions did not affect gait stability or spatiotemporal parameters at the two walking speeds studied. The variations in stability between visual conditions relative to normal vision were not expressive for MOS (< 4%), COMSEP (< 7%), or TtC (< 6%) at the two walking speeds. This lack of changes in stability may have been due to maintenance of the spatiotemporal characteristics because of the strong association between these characteristics. The adults studied can control stability without changing their gait patterns under different visual conditions, and lower light intensities do not increase the risk of falls
Highlights
Gait stability is controlled by the relationship between dynamic changes in the base of support (BOS) and displacements of the center of pressure and center of mass (COM), modeling this system as an “inverted pendulum”[1,2,3]
The same gait adaptations are observed in children walking in the dark[13], in subjects walking in a virtual reality environment which induces conflicts to the visual system[14,15], and in subjects with visual problems[12,16,17]
Most gait changes induced by alterations in the visual condition are evaluated in situations of normal vision or visual deprivation, whereas in daily life subjects are only exposed to environments with different light intensities
Summary
Gait stability is controlled by the relationship between dynamic changes in the base of support (BOS) and displacements of the center of pressure and center of mass (COM), modeling this system as an “inverted pendulum”[1,2,3]. The same gait adaptations are observed in children walking in the dark[13], in subjects walking in a virtual reality environment which induces conflicts to the visual system[14,15], and in subjects with visual problems[12,16,17] These patterns are adopted as a strategy to keep the COM close to the BOS, maintaining a careful gait as seen when walking in situations with an increased risk of slipping[7] or in elderly populations with a history of falls[18,19]. Most gait changes induced by alterations in the visual condition are evaluated in situations of normal vision or visual deprivation, whereas in daily life subjects are only exposed to environments with different light intensities. This was a pilot study conducted to obtain preliminary results that would permit the estimation of sample size for future studies
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