Higher intensity walking training in individuals with chronic motor incomplete spinal cord injury: A randomized clinical trial

Abstract

Background: The amount of walking practice may influence locomotor recovery in individuals with motor incomplete spinal cord injury (iSCI), although the contributions of exercise intensity are not well established. Objective: The purpose of this blinded-assessor randomized trial was to determine the contributions of exercise intensity on locomotor outcomes in individuals > 6 months following iSCI. Methods: Ambulatory individuals post-iSCI with walking speeds <1.0 m/s were assigned to ≤30 sessions of either high-intensity training (HIT: >70% heart rate [HR] reserve or ratings of perceived exertion [RPE]≥15) or low-intensity training (LIT; <40% HR reserve; RPE≤13). Assessments were performed at baseline, post-training and at 3-month follow-up evaluation, with primary outcomes of fastest walking speeds over 10 m and during graded treadmill exercise tests, and secondary clinical and metabolic outcomes. Results: Of 65 participants screened, 53 were randomized to HIT (n=28) or LIT (n=25) and completed 1489/1590 (94%) planned training sessions. Peak HRs and RPEs were greater during HIT (both p<0.001). Changes in fastest gait speeds overground were not significantly different between HIT and LIT when using Bonferroni corrections [α=0.025; mean post-training differences: 0.11 m/s (95% CI: 0.04–0.17 m/s), p=0.031], although gains in peak treadmill speed were significant [mean differences: 0.25 m/s (0.15 to 0.34 m/s), p-<0.001]. Secondary outcomes of 6-minute walk test (p=0.002) and combined measures of peak metabolic capacity and efficiency (p<0.001) were also greater with HIT. Conclusion: Greater gains in peak treadmill speed, 6-min walk, and selected metabolic outcomes were observed with HIT vs LIT in individuals with iSCI.