Between-limb synchronization for control of standing balance in individuals with stroke

Abstract

Individuals with stroke have reduced temporal synchronization of centre of pressure fluctuations under the feet when controlling quiet standing. The clinical significance of reduced synchronization remains to be determined, although it appears linked to increased medio-lateral sway and weight-bearing asymmetry.

Clinical Correlates of Between-Limb Synchronization of Standing Balance Control and Falls During Inpatient Stroke Rehabilitation

“…As has been reported previously, 7,10 absolute values of the correlation coefficients were greater for AP than ML COP. Changes in AP COP are mostly a result of the actions of ankle plantarflexors and dorsiflexors, whereas ML COP fluctuations under each limb are controlled by invertors and evertors.…”

“…Regarding our first objective, we hypothesized, consistent with previous work, 10 that reduced synchronization would be related to increased postural sway and increased weight-bearing asymmetry as measured using the force plate. Regarding the second objective, it was hypothesized that synchronization would be related to the underlying degree of impairment and to functional measures.…”

“…10 Among individuals with stroke, reduced between-limb synchronization was correlated with increased magnitude of postural sway and increased weight-bearing asymmetry. 10 Despite these relationships, we propose that measures of between-limb synchronization, overall postural sway, and weight-bearing symmetry are each independently important measures of quiet standing balance control poststroke and reveal unique control problems. We believe that between-limb synchronization may be specifically important as an index of poststroke balance control because it reflects impaired challenge of the central nervous system coupling control of 2 limbs to achieve shared control of balance.…”

“…Therefore, the strength of the correlation between COP fluctuations under both feet is thought to indicate between-limb synchronization of actions of both feet to maintain balance. 7,9,10 Among healthy individuals with no neurological conditions, anteroposterior (AP) COP fluctuations are highly positively correlated and mediolateral (ML) fluctuations are moderately negatively correlated. 7,9,10 Between-limb correlations in COP fluctuations are lower for individuals with stroke than for healthy controls.…”

A Retrospective Analysis of Post-Stroke Berg Balance Scale Scores: How Should Normal and At-Risk Scores Be Interpreted?

“…One compensatory strategy is to rely on the non-paretic (non-affected) limb while the paretic limb behaves like a fixed strut instead of actively contributing to standing-balance control. 22 A measure of centre of pressure (COP) displacement, under both feet combined, cannot reveal such compensatory strategies, 23,24 but using two force plates (one under each foot) allows a physiotherapist to calculate measures that tease out compensatory strategies and thus better indicate balance impairment.…”