Ankle Robotics Induces Ongoing Locomotor Plasticity with Delayed, Sustained Multi-Segmental Gait Improvements 17 Months After Training in Chronic Stroke

Background and Objectives: Robotics training improves gait after stroke, but no prior studies have investigated whether emerging long-term gait biomechanics improvements occur after training. We assessed the temporal profile of pre-post gait biomechanics changes after 9 weeks of dorsiflexion specific adaptive control ankle robot (AMBLE™) training, and at 9 weeks post-training and 17 months later in three persons with chronic stroke to probe for ongoing locomotor plasticity versus post-training disuse decay. Materials and Methods: Three densely hemiparetic subjects (mean ± SD), age 62 ± 7 years., stroke latency 8 ± 4 years, available for repeat testing from an original N = 24 robotics training cohort study, underwent three-dimensional gait analyses pre-post 9 weeks of AMBLE training, and then 9 weeks and 17 months after all robotics training ended. Results: We found that only 47% of total improvements in heel-first strikes and 31% increased paretic step length occurred pre-post training. Unexpectedly, all other biomechanical improvements manifested progressively 17 months after training ended, including ankle peak swing angle (∆ = 7°), dorsiflexion angular velocity (∆ = 23°/s), peak knee flexion (∆ = 11.1°) and hip flexion (∆ = 6°). Robotics prescription progressions in level of assistance and dorsiflexion target angle strongly correlated to gait biomechanical outcomes at 17 months, including improved heel-first strikes and peak dorsiflexion swing angle in this small sample. Conclusions: These findings show that initial improvements in foot–ankle function across training are followed by emergent biomechanical improvements in ankle, knee and hip kinematics across 17 months post-training, with delayed outcomes related to robotics prescription progression. The temporal profile of biomechanical adaptations might suggest delayed, progressive reduction in pathological multi-joint synergies of the hemiparetic leg. However, findings are exploratory and cannot establish causality, treatment efficacy or broad generalizability. Future research is needed to determine whether ankle robotics training can catalyze improvements in long-term gait biomechanical safety and efficiency in the chronic disease management of stroke.