Study Design Research design: A Phase III randomized clinical trial (RCT) will be performed using a crossover design and employing an exoskeletal-assisted walking intervention. The experimental arm will be compared to a usual activities (UA) arm, as the control, in 64 persons with chronic SCI (>6 month post injury) who are wheelchair-dependent for outdoor mobility in the community. Eligible participants will be randomized (within site) to one of two groups for 12 weeks (three months): Group 1 (n=32) will receive exoskeletal-assisted walking (WALK) first for 12 weeks then crossover UA for a second 12 weeks; Group 2 (n=32) will receive UA first for 12 weeks then cross-over to the WALK arm for 12 weeks of training. The WALK arm will consist of supervised exoskeletal-assisted walking training, three sessions per week (4-6 h/week) for 36 sessions for their second 12-week period. The UA arm will consist of identification of usual activities for each participant, encouragement to continue with these activities and attention by study team members throughout the 12-week UA arm. These activities will be recorded in a weekly log. A fixed answer format will be used to capture this information.