title: Gait variability in healthy old adults is more affected by a visual perturbation than by a cognitive or narrow step placement demand.
abstract: Gait variability measures have been linked to fall risk in older adults. However, challenging walking tasks may be required to elucidate increases in variability that arise from subtle age-related changes in cognitive processing and sensorimotor function. Hence, the study objective was to investigate the effects of visual perturbations, increased cognitive load, and narrowed step width on gait variability in healthy old and young adults. Eleven old (OA, 71.2±4.2 years) and twelve young (YA, 23.6±3.9 years) adults walked on a treadmill while watching a speed-matched virtual hallway. Subjects walked: (1) normally, (2) with mediolateral visual perturbations, (3) while performing a cognitive task (serial seven subtractions), and (4) with narrowed step width. We computed the mean and variability of step width (SW and SWV, respectively) and length (SL, SLV) over one 3-min trial per condition. Walking normally, old and young adults exhibited similar SWV and SLV. Visual perturbations significantly increased gait variability in old adults (by more than 100% for both SWV and SLV), but not young adults. The cognitive task and walking with narrowed step width did not show any effect on SWV or SLV in either group. The dramatic increase in step width variability when old adults were subjected to mediolateral visual perturbations was likely due to increased reliance on visual feedback for assessing whole-body position. Further work is needed to ascertain whether these findings may reflect sub-clinical balance deficits that could contribute to the increased fall risk seen with advancing age.
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Carrie A
authors.initials: CA
authors.lastname: Francis
authors.affiliation: Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA.
authors.forename: Jason R
authors.initials: JR
authors.lastname: Franz
authors.affiliation: Department of Bioengineering, University of California San Diego, San Diego, CA, USA; Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA, USA.
authors.forename: Shawn M
authors.initials: SM
authors.lastname: O'Connor
authors.affiliation: Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA; Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, WI, USA. Electronic address: thelen@engr.wisc.edu.
authors.forename: Darryl G
authors.initials: DG
authors.lastname: Thelen
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D003071:Cognition / Q000502:physiology*; D005080:Exercise Test; D056228:Feedback, Sensory / Q000502:physiology; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014796:Visual Perception / Q000502:physiology*; D016138:Walking / Q000502:physiology*
keywords: Aging; Dual task; Dynamic balance; Optical flow; Virtual reality