Poststroke hemiparesis impairs the rate but not magnitude of adaptation of spatial and temporal locomotor features

Abstract

Background: Persons with stroke and hemiparesis walk with a characteristic pattern of spatial and temporal asymmetry that is resistant to most traditional interventions. It was recently shown in nondisabled persons that the degree of walking symmetry can be readily altered via locomotor adaptation. However, it is unclear whether stroke-related brain damage affects the ability to adapt spatial or temporal gait symmetry.

Objective: Determine whether locomotor adaptation to a novel swing phase perturbation is impaired in persons with chronic stroke and hemiparesis.

Methods: Participants with ischemic stroke (14) and nondisabled controls (12) walked on a treadmill before, during, and after adaptation to a unilateral perturbing weight that resisted forward leg movement. Leg kinematics were measured bilaterally, including step length and single-limb support (SLS) time symmetry, limb angle center of oscillation, and interlimb phasing, and magnitude of "initial" and "late" locomotor adaptation rates were determined.

Results: All participants had similar magnitudes of adaptation and similar initial adaptation rates both spatially and temporally. All 14 participants with stroke and baseline asymmetry temporarily walked with improved SLS time symmetry after adaptation. However, late adaptation rates poststroke were decreased (took more strides to achieve adaptation) compared with controls.

Conclusions: Mild to moderate hemiparesis does not interfere with the initial acquisition of novel symmetrical gait patterns in both the spatial and temporal domains, though it does disrupt the rate at which "late" adaptive changes are produced. Impairment of the late, slow phase of learning may be an important rehabilitation consideration in this patient population.

Figure 1

A. Treadmill setup showing application of the resistive force and the method for calculating limb angles. Small open circles indicate marker positions. B. Time course of experimental conditions and testing periods.

Figure 2

A. Step-length symmetry over all conditions for a typical control (top) and participant with stroke, paretic leg perturbed (middle), and nonparetic leg perturbed (bottom). Each circle represents the average step length symmetry index for 3 consecutive strides. Arrows indicate the approximate transition point between the initial, fast and late, slow adaptation components. B-D. Group average step length symmetry indices (B), center-of-oscillation differences (C), and interlimb phasing (D). Collapsing across participant groups, asterisks indicate a significance of P < .05 from the testing period post hoc comparison of each versus Late Baseline. Late Baseline (LB), Early Adaptation (EA), Late Adaptation (LA), Early Postadaptation (EP), Late Postadaptation (LP) are shown. Error bars, ± 1 standard error of the mean. For all panels, dashed horizontal lines represent perfect symmetry.

Figure 3

A. SLS time symmetry over all conditions for a typical control (top) and participant with stroke, paretic leg perturbed (middle) and nonparetic leg perturbed (bottom): each circle represents the average SLS time symmetry index for 3 consecutive strides. Arrows indicate the approximate transition point between the initial, fast and late, slow adaptation components. B. Group average SLS time symmetry indices: group differences are evident at Late Baseline. Collapsing across participant groups, asterisk indicates significance of P < .05 from the testing period post hoc comparison of each versus Late Baseline (error bars, ±1 SEM). C. SLS time symmetry indices shown for all participants with stroke, paretic leg perturbed (top) and nonparetic leg perturbed (bottom), at 3 key time periods. Late Baseline (LB), Early Adaptation (EA), Late Adaptation (LA), Early Postadaptation (EP), Late Postadaptation (LP) are shown. For all panels, the dashed horizontal line indicates perfect symmetry.

Figure 4

A, B. Rates of adaptation, derived from the double exponential curve fits of averaged group data, indicating the number of strides required to achieve the initial, fast portion of adaptation (A) and the late, slow portion of adaptation (B). Both are shown for the measures of step length symmetry, SLS time symmetry, and center-of-oscillation differences. Note the break in the y-axis. Numbers above some columns indicate the number of strides required for the late, slow adaptation. Asterisks indicate significance of P < .05 from the control group 95% confidence interval.