Individuals with chronic stroke have long-term walking problems that limit community engagement and quality of life, lead to secondary disabilities, and increase healthcare costs and burden. These walking issues often persist despite rehabilitation. One novel target for stroke gait rehabilitation is interlimb coordination-the phase-dependent cyclical relation of the legs. Interlimb coordination is altered during walking after stroke, compromising walking stability, phase transitions, and responses to perturbation and contributing to motor compensation. It is unclear what neural pathways contribute to impaired interlimb coordination after stroke and what impact this has on walking-related outcomes. This proposal consists of two aims to address these issues, with the long-term goal of developing therapeutic interventions to improve interlimb coordination and walking after stroke. Aim 1 will identify which neural sources contribute to impaired interlimb coordination after stroke. During bilateral, cyclical recumbent stepping (analogue of walking), interlimb coordination will be assessed as relative leg phasing. During the task, transcranial magnetic stimulation and peripheral nerve stimulation will be applied to assess supraspinal, interhemispheric, spinal interneuronal, and sensory pathways. The relation of interlimb coordination with these outcomes will be assessed to determine potential contributors. Aim 2 will test the association between interlimb coordination and walking after stroke. Interlimb coordination will be quantified during split-belt treadmill walking, and associations with walking speed, endurance, mobility, independence, daily activity, quality of life, and community engagement will be tested. An additional exploratory aim will determine the effect of targeted neuromodulation on lower limb interlimb coordination. Electrical stimulation will be applied to three locations in a cross-over study: the primary motor cortex (supraspinal/interhemispheric), thoracolumbar spine (spinal interneuronal), and peripheral nerves (sensory).