Higher Intensity Walking Training in Individuals With Chronic Motor Incomplete Spinal Cord Injury: A Randomized Clinical Trial

BackgroundThe 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.ObjectiveThe purpose of this blinded-assessor randomized trial was to determine the contributions of exercise intensity on locomotor outcomes in individuals >6 months following iSCI.MethodsAmbulatory 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.ResultsOf 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 <i>P</i> < .001). Changes in fastest gait speeds overground were not significantly different between HIT and LIT when using Bonferroni corrections (α = .025; mean post-training differences: 0.11 m/s [95% CI: 0.04-0.17 m/s], <i>P</i> = .031), although gains in peak treadmill speed were significant (mean differences: 0.25 m/s [0.15-0.34 m/s], <i>p</i> < .001]. Secondary outcomes of 6-minute walk test (<i>P</i> = .002) and combined measures of peak metabolic capacity and efficiency (<i>P</i> < .001) were also greater with HIT.ConclusionGreater gains in peak treadmill speed, 6-minute walk, and selected metabolic outcomes were observed with HIT versus LIT in individuals with iSCI.Trial Registrationhttps://clinicaltrials.gov/; Unique Identifier: NCT03714997.