Paretic versus non-paretic stepping responses following pelvis perturbations in walking chronic-stage stroke survivors
Haarman et al. Journal of NeuroEngineering and Rehabilitation
Paretic versus non-paretic stepping responses following pelvis perturbations in walking chronic-stage stroke survivors
Juliet A. M. Haarman 0 2
Mark Vlutters 0 1
Richelle A. C. M. Olde Keizer 2
Edwin H. F. van Asseldonk 1
Jaap H. Buurke 2
Jasper Reenalda 2
Johan S. Rietman 1 2
Herman van der Kooij 1
0 Equal contributors
1 Department of Biomechanical Engineering, University of Twente , Horstring W119, PO Box 217, 7500 AE Enschede , The Netherlands
2 Roessingh Research and Development , Enschede , The Netherlands
Background: The effects of a stroke, such as hemiparesis, can severely hamper the ability to walk and to maintain balance during gait. Providing support to stroke survivors through a robotic exoskeleton, either to provide training or daily-life support, requires an understanding of the balance impairments that result from a stroke. Here, we investigate the differences between the paretic and non-paretic leg in making recovery steps to restore balance following a disturbance during walking. Methods: We perturbed 10 chronic-stage stroke survivors during walking using mediolateral perturbations of various amplitudes. Kinematic data as well as gluteus medius muscle activity levels during the first recovery step were recorded and analyzed. Results: The results show that this group of subjects is able to modulate foot placement in response to the perturbations regardless of the leg being paretic or not. Modulation in gluteus medius activity with the various perturbations is in line with this observation. In general, the foot of the paretic leg was laterally placed further away from the center of mass than that of the non-paretic leg, while subjects spent more time standing on the non-paretic leg. Conclusions: The findings suggest that, though stroke-related gait characteristics are present, the modulation with the various perturbations remains unaffected. This might be because all subjects were only mildly impaired, or because these stepping responses partly occur through involuntary pathways which remain unaffected by the complications after the stroke.
Stroke; Balance during gait; Perturbed walking; Reactive foot placement; Muscle activity changes
Background
Stroke survivors often experience problems with
maintaining their balance. A variety of neurological deficits
can hamper balance control during walking, such as
hemiparesis, sensory impairments, as well as cognitive
problems such as fear of falling. As a consequence, fall
rates in stroke survivors are 2–8 times higher than those
in healthy, age-matched subjects [
1
]. In general,
especially balance control in the frontal plane is often
considered challenging, requiring adequate foot placement
to continue walking [
2
]. This might be an additional
challenge when suffering from hemiparesis following a
stroke, which could lead to differences in recovery steps
made with the paretic and the non-paretic leg in
response to a disturbance during walking. To reduce the
fall risk of stroke survivors and make their rehabilitation
more effective, it is required to characterize how balance
control is affected by a stroke. Such knowledge might be
used to provide limb-specific support in robot-assisted
gait rehabilitation.
Stroke survivors typically show differences in gait
characteristics between the paretic and non-paretic leg
during unperturbed walking, for example as a result of
decreased motor control in the paretic leg. In a study by
Balasubramanian et al. subjects placed the paretic leg at
an increased lateral distance from the pelvis compared
to the non-paretic leg in mediolateral (ML) foot
placement during unperturbed walking [
3
]. However, no
differences in step width were found with regard to the leg
used for stepping. It is therefore of importance to
consider both legs individually, in a body referenced frame
such as that of the center of mass (COM). Dean et al.
studied the relation between gluteus medius muscle
activity in the swing leg and both the ML position and
velocity of the COM relative to the stance foot [
4
]. For low
fall-risk subjects the results suggest a stronger activity
modulation in the non-paretic swing leg than in the
paretic swing leg, though it did not show how both legs
respond to actual destabilizing conditions such as external
perturbations.
Perturbations can be used to affect the body state,
such as the position and velocity of the COM relative to
the stance foot. This may lead to adjustments in foot
placement location and timing to maintain balance. In
Krasovsky et al. perturbations were applied by
unexpectedly arresting the ankle of the leg at early swing [
5
].
Stroke survivors showed shorter step lengths and shorter
swing times compared to healthy controls when stepping
in response to perturbations applied to the non-paretic
swing leg. Furthermore, in Hak et al. continuous ML
support surface translations were used to assess if and
how low-fall ri (...truncated)