Abstract
We investigated the neuromuscular contributions to kinematic variability and thus step to step adjustments in posture and foot placement across a range of walking speeds in response to optical flow perturbations of different amplitudes using a custom virtual environment. We found that perturbations significantly increased step width, decreased step length, and elicited larger trunk sway compared to normal walking. However, perturbation-induced effects on the corresponding variabilities of these measurements were much more profound. Consistent with our hypotheses, we found that: (1) perturbations increased EMG activity of the gluteus medius and postural control muscles during leg swing, and increased antagonist leg muscle coactivation during limb loading in early stance, and (2) changes in the magnitude of step to step adjustments in postural sway and lateral foot placement positively correlated with those of postural control and gluteus medius muscle activities, respectively, in response to perturbations. However, (3) interactions between walking speed and susceptibility to perturbations, when present, were more complex than anticipated. Our study provides important mechanistic neuromuscular insight into walking balance control and important reference values for the emergence of balance impairment.
Highlights
Electromyographic (EMG) recordings of muscle activity during perturbed walking can provide insight into the extent to which dynamic balance corrections are neurally mediated via muscular actions
A hip abductor, gluteus medius (GM) activity increased by an average of up to 15% during early to midstance (p’s < 0.024), and by an average of up to 29% during terminal swing (p = 0.001; Fig. 3A), concurrent with significant increases in medial hamstring (MH) activity (p = 0.017; Fig. 3B)
We found that perturbations significantly increased step width, decreased step length, and elicited larger trunk sway compared to normal, unperturbed walking
Summary
Electromyographic (EMG) recordings of muscle activity during perturbed walking can provide insight into the extent to which dynamic balance corrections are neurally mediated via muscular actions. We recently proposed that optical flow perturbations elicit postural disturbances in walking via visuomotor entrainment, wherein head and trunk kinematics synchronize to the perturbation via postural adjustments to instinctively unify visual with somatosensory and vestibular feedback[10] We suspect that these postural disturbances subsequently elicit step to step adjustments in foot placement, in the mediolateral direction, to preserve whole-body balance. We hypothesized that perturbations would increase EMG activity of the gluteus medius and postural control muscles during leg swing, and increase the coactivation of antagonistic leg muscles during limb loading in early stance. We hypothesized that changes in the magnitude of step to step adjustments in postural sway and lateral foot placement would be positively correlated with those of postural control and gluteus medius muscle activities, respectively, in response to perturbations. We hypothesized that perturbation-induced changes in kinematic variability and EMG activity would be smaller at slower walking speeds
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
