Résumé
Motor imagery training (MIT; the mental rehearsal of movement without physical execution) shows promise for enhancing motor recovery after stroke. Previous studies suggest MIT can improve force steadiness, which could aid post-stroke motor control. However, whether benefits are task-dependent remains untested. Here, we examined the impact of MIT on a force steadiness task under two conditions: congruent (i.e., matching the task during MIT) and incongruent (opposing the task during MIT). Individuals with upper-limb impairment ≥3 months post-stroke (N = 12) and healthy older adults (HOA; N = 12) completed four MIT sessions of an everyday task involving an isometric elbow flexion. Before and after MIT, participants performed ramped elbow flexion and extensions in an isometric myograph. Force steadiness was quantified as the coefficient of variation of torque (CVtorque; primary outcome), and Cohen’s d effect sizes were calculated to quantify change in CVtorque (post vs. pre) separately for each group. Preliminary results (n = 5 stroke, n = 7 HOA) suggest that following MIT (△CVtorque; post minus pre) elbow flexion CVtorque decreased in both groups (HOA: △CVtorque= -2.60±3.50, d = -0.74; stroke: △CVtorque= -0.95±0.38, d = -2.48). Conversely, elbow extension CVtorque increased (HOA: △CVtorque = 1.55±1.80, d = 0.86; stroke: △CVtorque = 3.16±7.85, d = 0.40). In showing that CVtorque only improved in the congruent condition (i.e., elbow flexion), findings suggest that improvements observed after MIT are task-dependent, and may not generalize across movements. Overall, findings inform the application of MIT for motor recovery after stroke.
