The influence of increased passive stiffness of the trunk and hips on balance control during reactive stepping
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Date
2019-07
Authors
Pretty, Steven P.
Armstrong, Daniel
Weaver, Tyler B.
Laing, Andrew C.
Journal Title
Journal ISSN
Volume Title
Publisher
Elsevier
Abstract
Background
Age-related changes, which include increased trunk and hip stiffness, negatively influence postural balance. While previous studies suggest no net-effect of trunk and hip stiffness on initial trip-recovery responses, no study to date has examined potential effects during the dynamic restabilisation phase following foot contact.
Research question
Does increased trunk and hip stiffness, in isolation from other ageing effects, negatively influence balance during the restabilisation phase of reactive stepping.
Methods
Balance perturbations were applied using a tether-release paradigm, which required participants to react with a single-forward step. Sixteen young adults completed two blocks of testing: a baseline and an increased stiffness (corset) condition. Whole-body kinematics were utilized to estimate spatial step parameters, center of mass (COM), COM incongruity (peak - final position) and time to restabilisation, in anteroposterior (AP) and mediolateral (ML) directions.
Results
In the corset condition, peak COM displacement was increased in both directions (p < 0.024), which drove reductions in minimum margins of stability (p < 0.032) as step width and length were unchanged (p > 0.233). Increased passive stiffness also increased the magnitude and variability of peak shear ground reaction force, COM incongruity, and time to restabilisation in the ML (but not AP) direction (p < 0.027).
Significance
In contrast to previous literature, increased stiffness resulted in greater peak COM displacement in both directions. Our results suggest increased trunk and hip stiffness have detrimental effects on dynamic stability following a reactive step, particularly in the ML direction. Observed increases in magnitude and variability of COM incongruity suggest the likelihood of a sufficiently large loss of ML stability - requiring additional steps - was increased by stiffening of the hips and trunk. The current findings suggest interventions aiming to mobilize the trunk and hips, in conjunction with strengthening, could improve balance and reduce the risk of falls.
Description
The final publication is available at Elsevier via https://doi.org/10.1016/j.gaitpost.2019.05.018. © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
Keywords
balance, stiffness, reactive stepping, rehabilitation