Between-leg asymmetry in automatic postural responses to stance perturbations in people with Parkinson's disease

Abstract

Background: People with Parkinson's disease (PwPD) showed impairments of balance control which can be aggravated by the presence of higher interlateral postural asymmetry caused by a distinct dopaminergic loss in the substantia nigra between cerebral hemispheres.

Research question: We evaluate asymmetries between the more and the less affected leg in PwPD in responses to unanticipated stance perturbations.

Methods: Sixteen 16 PwPD participated in the experiment that consisted of recovering a stable upright stance, keeping the feet in place, in response to a perturbation caused by a sudden release of a load equivalent to 7 % of the participant's body mass. Anterior displacement and velocity of the center of pressure (CoP), the latency of gastrocnemius medialis muscle (GM) activation onset, rate of GM activation, and normalized magnitude of muscular activation were analyzed.

Results: Analysis revealed significantly rate (p = 0.04) and magnitude (p = 0.02) higher activation of GM in the less affected limb. No significant effects of the leg were found for GM activation latency or CoP-related variables.

Significance: There is a higher contribution of the less affected leg in automatic postural responses in PwPD.

Keywords: Asymmetries; Balance; Postural control; Reactive postural adjustments.