On the Relative Contribution of the Paretic Leg to the Control of Posture After Stroke

Abstract

Background. Reduced postural steadiness and asymmetry of weight bearing are characteristic for posture after stroke. Objective. To examine the relative contribution of each leg to postural control in a cohort of 33 stroke patients at 5 stages during 3 months of inpatient rehabilitation, while taking clinical scores of sensory and motor impairments of the paretic leg into account. Methods. Participants were instructed to stand as symmetrically as possible under both sensory and cognitive manipulations, while a dual-plate force platform was used to assess the contribution of each leg to postural control, quantified by the amplitude, velocity, and regularity of recorded center-of-pressure trajectories. A greater contribution of the nonparetic leg was expected, particularly in patients with ankle clonus, disturbed sensibility, and lack of selective muscle control on the paretic side. Results. With follow-up assessments, weight-bearing asymmetry and postural steadiness improved. Patients strongly relied on visual information. When attention was distracted by having the patients perform an arithmetic task, weight-bearing asymmetry increased, suggesting that symmetric weight bearing was attention demanding. Patients with severe motor impairments of the paretic leg showed greater static (weight-bearing) and dynamic (lateralized control) asymmetries than patients with limited motor impairments, whereas postural steadiness did not differ between these subgroups. Disturbed sensation did not affect weight-bearing asymmetry, postural steadiness, or lateralized control. Conclusion. Patients with severe motor impairments of the paretic leg employ an effective compensatory strategy consisting of asymmetric weight bearing and lateralized control.