Understanding Bilateral Motor Coordination in Stroke Using the Towel Folding Task: An Exploratory Biomechanical Study

Abstract Objectives Coordination deficits in bilateral upper limbs make daily activities more difficult for stroke survivors. Previous studies showed worse kinematics during unilateral tasks compared to healthy individuals, but this was unclear for bimanual tasks. We aim to assess the potential of the towel folding task from the Wolf Motor Function Assessment as a measure of bimanual control by examining kinematic differences between stroke survivors and healthy individuals and correlating these differences with clinical parameters in the stroke group. Methods This was a cross-sectional design. Seventeen people with stroke and sixteen healthy individuals participated. Vicon motion capture obtained kinematics of bilateral upper limbs during the task, including movement time, initiation delay, velocity, trunk displacement, smoothness, and inter-/intra-limb coordination. Statistical analyses compared groups and correlated kinematic variables with clinical parameters. Results Stroke survivors had longer movement times ( P < .001, Cohen’s d = 1.396), slower initiation ( P < .001, Cohen’s d = 0.797), lower max velocity ( P = .026, Cohen’s d = −.815; P < .001, Cohen’s d = −2.156; and P = .005, Cohen’s d = −.736; respectively), greater trunk displacement ( P < .001, Cohen’s d = 2.173 and P < .001, Cohen’s d = 1.727, respectively), less smoothness ( P = .031, Cohen’s d = 0.883 and P < .001, Cohen’s d = .725, respectively), and altered inter-/intra-limb coordination. Regarding bilateral elbow-elbow coordination, stroke group exhibited decreased in-phase patterns ( P < .001, partial η² = .368) and increased anti-phase and non-hemiplegic elbow dominancy patterns ( P = .001, partial η² = .298 and P = .004, partial η² = .244, respectively). Regarding bilateral shoulder-shoulder coordination, stroke group showed decreased hemiplegic shoulder leading patterns ( P = .010, partial η² = .196) and increased anti-phase and non-hemiplegic shoulder dominancy patterns ( P = .001, partial η² = .315 and P < .001, partial η² = .463, respectively). For hemiplegic shoulder-elbow coordination, stroke group showed decreased anti-phase patterns ( P < .001, partial η² = .382) and increased elbow dominancy P atterns ( P < .001, partial η² = .324). Fugl-Meyer Assessment scores positively correlated with smoothness and hemiplegic shoulder-elbow coordination (r = −.500, P = .039 and r = .600, P = .010, respectively), while Action Research Arm Test scores negatively correlated with movement initiation delay (r = −.600, P = .010). Conclusions This study enhances understanding of the folding towel task and may provide metrics to quantify bilateral coordination task performance in stroke survivors.