Bilateral motor coordination during upper limb symmetric pushing movements at two levels of force resistance in healthy and post-stroke individuals

Abstract

Background: Impairments of the upper limb (UL) are common after a stroke and may affect bilateral coordination. A better understanding of UL bilateral coordination is required for designing innovative rehabilitation strategies.

Objective: To assess bilateral coordination after stroke using time-distance, velocity and force parameters during an UL bilateral task performed by simultaneously pushing handles on a bilateral exerciser at two levels of force.

Methods: Two groups were included to assess bilateral coordination on a newly designed bimanual exerciser- One group of individuals at least 3 months post-stroke (n = 19) with moderate impairment and one group of healthy individuals (n = 20). Participants performed linear movements by pushing simultaneously with both hands on instrumented handles. The task consisted of two one-minute trials performed in sitting at two levels of participants' maximum force (MF): 30% and 15%, with visual feedback. Time-distance parameters, spatial, velocity and force profiles were compared between groups, between levels of resistance and the first part (0-50%) and entire duration of the pushing cycles (0-100%).

Results: The mean pushing time was longer at 30% MF compared to 15% MF in the stroke group. Spatial profiles, represented by hand positions on the rail, revealed that the paretic hand lagged slightly behind throughout the cycle. For velocity, both groups displayed good coordination. It was less coupled at 30% than 15% MF and a trend was observed toward more lag occurrence in the stroke group. Except for lower forces on the paretic side in the stroke group, the shape of the force profiles was similar between groups, sides and levels of resistance. For all parameters, the coordination was good up to 75% of the pushing cycle and decreased toward the end of the cycle.

Conclusions: Individuals after stroke presented with overall spatial and temporal coupling of the UL during bilateral pushing movements. The relay of information at different levels of the nervous system might explain the coordinated pushing movements and might be interesting for training UL coordination.

Keywords: Bilateral coordination; Exerciser; Rehabilitation; Stroke; Upper limb.