A Robust Method to Estimate the Largest Lyapunov Exponent of Noisy Signals: A Revision to the Rosenstein’s Algorithm

Mehdizadeh, Sina

doi:10.1101/381111

Cited by 2 publications

(1 citation statement)

References 20 publications

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“…For each epoch of 30 strides, we determined the R 2 of this regression. As a measure of local dynamic stability, local divergence exponents were determined (Bruijn et al, 2013; Bruijn, 2021; Mehdizadeh, 2019; Rosenstein et al, 1993) by first constructing a six-dimensional state space based on time-delayed (25 samples) copies of the 3D center of mass velocity. To this end, the signal was resampled so that on average each stride was 100 samples in length.…”

Section: Methodsmentioning

confidence: 99%

Can foot placement during gait be trained? Adaptations in stability control when ankle moments are constrained

Hoogstad

Leeuwen

Dieën

et al. 2021

Preprint

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Accurate coordination of mediolateral foot placement, relative to the center of mass kinematic state, is one of the mechanisms which ensures mediolateral stability during human walking. Previously, we found that shoes constraining ankle moments decreased foot placement accuracy, presumably by impairing control over movement of the swing leg. As such, ankle moment constraints can be seen as a perturbation of foot placement. Direct mechanical perturbations of the swing leg trajectory can improve foot placement accuracy as an after-effect. Here, we asked whether constrained ankle moments could have a similar effect. If confirmed, this would offer a simple training tool for individuals with impaired foot placement control. Participants (n=19) walked in three conditions; normal (baseline, 10 minutes), while wearing shoes constraining ankle moments (training, 15 minutes), and normal again (after-effects, 10 minutes). Foot placement accuracy was calculated as the percentage of variance in foot placement that could be predicted based on the center of mass kinematic state in the preceding swing phase. When walking with constrained ankle moments, foot placement accuracy decreased initially compared to baseline, but it gradually improved over time. In the after-effect condition, foot placement accuracy was higher than during baseline, but this difference was not significant. When walking with constrained ankle moments, we observed increased step width, decreased stride time and reduced local dynamic stability. In conclusion, constraining ankle moment control deteriorates foot placement accuracy. A non-significant trend towards improved foot placement accuracy after prolonged exposure to constrained ankle moments, allows for speculation on a training potential.

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Section: Methodsmentioning

confidence: 99%

Can foot placement during gait be trained? Adaptations in stability control when ankle moments are constrained

Hoogstad

Leeuwen

Dieën

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

Changes in Seasonal Footwear Elicited Alterations in Gait Kinematics but Not Stability

Garrah,

Best,

2023

Preprint

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During daily walking, humans might contend with various perturbations from slippery surfaces in the winter to uneven sidewalks in the summer. Inertial sensors enable investigations of how humans maintain balance under these natural conditions, but conducting these outdoor studies has practical considerations that might influence study results, such as the selection of footwear under different weather conditions. Our study investigates the effects of winter and summer shoe types on gait patterns, specifically whether different shoe types induce changes in gait stability measures under the same walking environment. Twelve healthy adult participants walked indoors with winter and summer shoes while their gait kinematics were recorded using an inertial sensor-based motion capture system. Spatiotemporal measures, body kinematics, stability measures (minimum margin of stability and local divergence exponent), and stepping regressions were calculated to evaluate differences between walking in summer and winter shoes. Statistical significance was determined by paired t-tests. Varying shoe types altered spatiotemporal and kinematic measures, such as increased stride time and stance time while wearing winter shoes, but increased step width and reliance on stepping were the only stability-related changes found. Our study provides insights into the influence of footwear for inertial sensor-based gait studies in real environments, aiding the analysis and interpretation of those studies to augment our understanding of natural stability behavior.

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A Robust Method to Estimate the Largest Lyapunov Exponent of Noisy Signals: A Revision to the Rosenstein’s Algorithm

Cited by 2 publications

References 20 publications

Can foot placement during gait be trained? Adaptations in stability control when ankle moments are constrained

Can foot placement during gait be trained? Adaptations in stability control when ankle moments are constrained

Changes in Seasonal Footwear Elicited Alterations in Gait Kinematics but Not Stability

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