Amplitude effects of medio-lateral mechanical and visual perturbations on gait

Dynamic stability of superior vs. inferior body segments in individuals with transtibial amputation walking in destabilizing environments

“…3B, Table 3) dynamic instability of the ML COM movements of all body segments. This indicates that visual and walking surface perturbations significantly affect whole body stability, as previously shown (McAndrew et al, 2011; Sinitski et al, 2012; Terry et al, 2012). Importantly, the present findings extend these prior results to other body segments.…”

“…2) with incommensurate frequencies (McAndrew et al, 2010; Beurskens et al, 2014): $$A\left(t\right)=A_W\left[1.0\sin \right(0.16\mathrm{x}2\pi t)+0.8\sin (0.21x2\pi t)+1.4\sin (0.24\mathrm{x}2\pi t)+0.5\sin (0.49\mathrm{x}2\pi t\left)\right],$$ where A(t) was the perturbation amplitude in meters, A w was a weighting factor in meters and t was time in seconds. Perturbation magnitudes were set to A w =0.05 for PLAT and to A w =0.50 for VIS to generate approximately comparable responses for each perturbation type (Terry et al, 2012). Throughout each trial, participants’ head orientation was monitored visually to ensure they were looking at the horizon directly in front of them.…”

“…When exposed to side to side perturbations of the visual field or walking surface, healthy young adults exhibited greater dynamic instability (McAndrew et al, 2011; Sinitski et al, 2012) and increased stepping and trunk movement variability (McAndrew et al, 2010). These became more pronounced with larger perturbation amplitudes (Sinitksi et al, 2012; Terry et al, 2012). In some studies, individuals with amputations similarly adopted a slower more conservative gait on challenging surfaces (Paysant et al, 2006; Kendell et al, 2010; Lamoth et al, 2010).…”

Estabilidade da marcha de adultos em diferentes condições visuais: estudo piloto

“…In adults, visual deprivation during walking induces negative changes in the spatiotemporal patterns of gait, such as a reduction in walking speed and step length and an increase in double support duration [10][11][12] . 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 . Apparently, 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 .…”

“…In the case of adaptation to slower walking speeds, step length should decrease to prevent the loss of stability and risk of falls 7 . Visual perturbations do not impose changes during walking, but rather cause motor adaptations characterized by relatively individual responses to permit gait control 15 . During visual deprivation, these alterations in gait correction are seen in situations of overcoming obstacles 22 and in the control of gait termination 25 .…”