Identifying differences in gait adaptability across various speeds using movement synergy analysis

Abstract

IntroductionThe aim of this study was to identify movement synergies during normal-walking that can differentiate healthy adults in terms of gait adaptability at various speeds. To this end, the association between movement synergies and lower-limb coordination variability or Deviation Phase (DP) was investigated. A secondary aim of this study included an investigation into the moderating effect of these movement synergies on the relationship between DP and the smoothness of arm-swing motion quantified as the normalised jerk index (NJI).MethodA principal component analysis of whole-body marker trajectories from normal-walking treadmill trials at 0.8m/s, 1.2m/s and 1.6m/s was undertaken. Both DP and NJI were derived from approx. 8 minutes of perturbed-walking treadmill trials. Principal movement components, PMk, were derived and the RMS of the 2nd-order differentiation of these PMk (PAkRMS) were included as independent variables representing the magnitude of neuromuscular control in each PMk. The PAkRMS were input into separate maximal linear mixed-effects regression models to explain the variance in DP and (DP × NJI). A stepwise elimination of terms and comparison of models using Anova identified optimal models for both aims.ResultsAmong the first 7 validated PMk, PA4RMS (double-support phase) was identified as an optimal model and demonstrated a significant negative effect on DP however this effect may differ considerably across walking-speeds. An optimal model for describing the variance in (DP × NJI) included a fixed-effect of PA6RMS (Left – Right side weight transfer). Within-participant clustering was prevalent within both optimal models.InterpretationThe hypotheses that individuals who exhibited greater control on specific kinematic synergies would exhibit variations during perturbed walking was substantiated. Supporting evidence for the role of movement synergies during the double-support phase of gait in proactively correcting balance was presented. The potential influence of leg dominance on gait adaptability was also discussed. Future studies should investigate further the role of walking-speed and leg dominance on movement synergies and look to generalize these findings to patient populations.HighlightsBaseline movement synergies representing terminal-swing and double-support phases of gait were found to have significant negative effects on lower-limb coordination variability during perturbed-walking trials at various speeds.Movement synergies related to the double-support phase and weight transfer events of gait were determined to have a negative moderating effect on the translation of lower-limb coordination variability into upper-limb postural corrections.Evidence was presented for the important role of the double-stance phase of gait in gait adaptability while leg dominance was shown to play a potential role in differentiating healthy adults in this study.

Slow walking synergies reveal a functional role for arm swing asymmetry in healthy adults: A principal component analysis with relation to mechanical work

“…Interdependencies between such gait balance control strategies relevant to step-to-step transitions (i.e. push-off modulation, lateral ankle and foot placement mechanisms) have been identified in the literature (17,57). The interdependencies between lateral ankle and foot placement mechanisms were found to be consistent with varied perturbation direction, however only a weak association with the push-off mechanism was found.…”

“…A leave-one out cross-validation revealed that the first 4 PMk did not change by >15° and these were deemed valid (34). The first PM explaining 61.7% of the overall variance was chosen for further analysis only as this primary PM has been identified in previous studies as the basic inverted-pendulum motion of gait and as such is of specific relevance to this study's aims (17,42). With this primary PM the number of zero-crossings in its corresponding PAk time-series were counted for each participant (34,36), thus formulating the independent variable Nk for further analysis.…”

“…It is of frequent practice in research to challenge the central nervous system (CNS) of participants for example by creating dual-task conditions (15), inducing a perturbation (17), standing on unstable support surfaces (18) or walking more slowly/quickly than usual (19). Challenging subjects to intentionally walk slower than normal induces lower inter-limb coordination and increased attentional requirements (20).…”