Approximately 15,000 Veterans are hospitalized for stroke each year with new cases costing an estimated $111 million for acute inpatient, $75 million for post-acute inpatient, and $88 million for follow-up care over 6 months post-stroke. The investigators have previously established the effectiveness of a backward walking training program to improve gait and balance in post-stroke Veterans. To best serve Veterans in this era of personalized medicine, there is a current need to determine the appropriate training dose as well as which post-stroke Veterans would most benefit. This study addresses both needs as it will 1) test responses to two different doses (18 vs. 27 sessions) of backward walking training and 2) assess brain activity, measured by magnetic resonance imaging, before and after training intervention to determine its ability to predict rehabilitation response as well as brain mechanisms of behavioral change.