Gert Kwakkel

Background Recovery of quiet standing balance early poststroke has been poorly investigated using repeated measurements. Objective To investigate (1) the time course of steady-state balance in terms of postural stability and inter-limb symmetry, and (2) longitudinal associations with lower limb motor recovery in the first 3 months poststroke. Methods Forty-eight hemiparetic subjects (age: 58.9 ± 16.1 years) were evaluated at weeks 3, 5, 8, and 12 poststroke. Motor impairments concerned the Fugl-Meyer assessment (FM-LE) and Motricity Index total score (MI-LE) or ankle item separately (MI-ankle). Postural stability during quiet 2-legged stance was calculated as the net center-of-pressure area (COP Area ) and direction-dependent velocities (COP Vel-ML and COP Vel-AP ). Dynamic control asymmetry (DCA) and weight-bearing asymmetry (WBA) estimated inter-limb symmetries in balance control and loading. Linear mixed models determined (1) time-dependent change and (2) the between- and within-subject associations between motor impairments and postural stability or inter-limb symmetry. Results Time-dependent improvements were significant for FM-LE, MI-LE, MI-ankle, COP Area , COP Vel-ML , and COP Vel-AP , and tended to plateau by week 8. DCA and WBA did not exhibit significant change. Between-subject analyses yielded significant regression coefficients for FM-LE, MI-LE, and MI-ankle scores with COP Area , COP Vel-ML , and COP Vel-AP up until week 8, and with WBA until week 12. Within-subject regression coefficients of motor recovery with change in COP Area , COP Vel-ML , COP Vel-AP , DCA, or WBA were generally non-significant. Conclusions Postural stability improved significantly in the first 8 weeks poststroke, independent of lower limb motor recovery at the most affected side within subjects. Our findings suggest that subjects preferred to compensate with their less affected side, making metrics reflecting inter-limb asymmetries in balance invariant for change early poststroke. Clinical Trial Registration: Clinicaltrials.gov. unique identifier NCT03728036.