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 three minute 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% in 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.

Balance and gait in the elderly: A contemporary review

“…They found that ML visual perturbations significantly increased gait variability (+152% step width variability and + 131% step length variability) in older adults but not younger adults compared to the normal condition, suggesting that older adults depend more on visual feedback for whole‐body positioning. Older adults also walked with 5% shorter step length in the ML visual perturbation condition, a significant change compared to the no visual perturbations condition . Figure illustrates an example of a motion capture system using anatomically placed markers.…”

“…Older adults also walked with 5% shorter step length in the ML visual perturbation condition, a significant change compared to the no visual perturbations condition. 45 Figure 3 illustrates an example of a motion capture system using anatomically placed markers. Similarly, Franz et al 46 studied old and young subjects who were instructed to walk on a treadmill at their preferred speed while viewing a speed-matched virtual reality hallway in the presence and absence of continuous ML visual perturbations.…”

Neuroimaging of Human Balance Control: A Systematic Review

“…Walking balance control is especially dynamic, involving coordinated adjustments in posture (i.e., head and trunk stabilization) and foot placement from step to step (Bauby and Kuo, 2000; Kay and Warren, 2001; Donelan et al, 2004; Rankin et al, 2014). Particularly in unpredictable and challenging environmental conditions, these adjustments depend on the integration of reliable sensory feedback and the planning and execution of appropriate motor responses (O'Connor and Kuo, 2009; O'Connor et al, 2012; Francis et al, 2015; Franz et al, 2015, 2016; Goodworth et al, 2015). Accordingly, sensory and mechanical perturbations are increasingly used to study corrective motor responses in standing and walking and the onset and progression of balance deficits.…”

“…Accordingly, sensory and mechanical perturbations are increasingly used to study corrective motor responses in standing and walking and the onset and progression of balance deficits. Sensory perturbations may include those of visual (e.g., optical flow) (O'Connor and Kuo, 2009; O'Connor et al, 2012; Francis et al, 2015; Franz et al, 2015, 2016), somatosensory (e.g., tendon vibration) (Gurfinkel et al, 1976; Hay et al, 1996; Bove et al, 2003; Mullie and Duclos, 2014), or vestibular feedback (e.g., galvanic stimulation) (Day et al, 1993; Fitzpatrick et al, 1994; Bent et al, 2002; Dakin et al, 2007; Dalton et al, 2014), whereas mechanical perturbations most frequently incorporate support surface translations (Sinitksi et al, 2012; Aprigliano et al, 2016). Cortical activity and high-order cognitive processes are highly involved in the planning and execution of these motor responses.…”

“…Human balance control investigations have primarily focused on quantifying motor responses based on kinematic measurements such as movement variability and dynamic stability and/or kinetic measurements such as center of pressure and angular momentum (O'Connor and Kuo, 2009; McAndrew et al, 2011; Francis et al, 2015; Sheehan et al, 2015). These studies are rapidly accelerating our scientific understanding of human balance control, with exciting translational implications for the diagnosis and rehabilitation of people at risk of falls.…”