STRENGTH REQUIREMENTS AND ENERGY EFFICIENCY OF DIFFERENT STAIR-STEPPING STRATEGIES IN PERSONS WITH CHRONIC STROKE AND HEALTHY ADULTS
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The majority of stroke survivors return to living in the community; however, muscle weakness and cardiovascular deconditioning can restrict mobility, limit community access and independence, particularly when challenging activities like stair negotiation are involved. A “step-by-step” (SBS) strategy (both feet per step) may be adopted in lieu of a “step-over-step” (SOS) method (one foot per step) to increase stability and off-load the paretic limb though the physical demands of the two methods are unknown. The main objective of this thesis was to investigate the strength and energy demands of the two stair-stepping strategies in chronic stroke compared to healthy adults. The first study identified the relative strength and aerobic demands of both strategies. The results showed that the stroke group produced similar peak joint moments compared to controls, despite their slower cadence suggesting that the stroke group exerts comparable ‘effort’ to move more slowly. The SBS method was associated with lower strength costs (relative to individuals’ maximum strength output) than SOS, however aerobic cost was significantly higher. The second study identified the mechanical energy expenditures (MEEs) and transfers related to both strategies. The MEEs were found to be lower when the SBS strategy was used. Though expenditures were similar between groups, the stroke group had higher expenditures associated with the work of the less affected knee extensors (lead limb) during ascent and descent and controls exhibited higher expenditures for the plantarflexors during ascent. The reduced output of the trail (affected) limb plantarflexors likely resulted in the increased workload of the knee extensors. Overall, the aerobic cost per step was higher in stroke, particularly during descent, suggesting that in addition to reducing cadence, persons with stroke may be co-contracting to increase stabilization during descent, thus increasing oxygen demands. This thesis provides novel information on the physical demands associated with two methods of stair negotiation demonstrating that the SBS strategy might be better suited to persons with chronic stroke by minimizing the strength demands on the paretic side, but the benefit comes at an elevated aerobic cost. This information is valuable to rehabilitation professionals engaged in retraining mobility to facilitate community reintegration.