A more symmetrical gait after split-belt treadmill walking increases the effort in paretic plantar flexors in people post-stroke.

OBJECTIVE To determine if the level of effort in paretic plantar flexors during gait could be a factor in explaining locomotor asymmetry. DESIGN Cross-sectional study. SUBJECTS Twenty individuals with chronic stroke (mean age 49.4 years (standard deviation 13.2). METHODS Participants walked on a split-belt treadmill for 3 periods: baseline at self-selected speed; adaptation with the belt speed doubled on the non-paretic side; and post-adaptation at self-selected speed. Kinematic and kinetic data were recorded. The efforts were estimated with the muscular utilization ratio. Pearson correlation coefficients were used to assess the relationships between the paretic plantar flexor level of effort at baseline and changes in spatiotemporal gait parameters and joint moments after split-belt treadmill walking. In addition, in a subgroup of 12 asymmetrical individuals, paretic plantar flexor efforts were compared between periods (baseline (asymmetrical) and post-adaptation (symmetrical)) with paired Student's t-tests. RESULTS Baseline level of effort in plantar flexors was negatively related to changes in paretic plantar flexion moments (r = -0.70; p = 0.001) and changes in non-paretic step length (r = -0.65; p = 0.003). A more symmetrical spatiotemporal gait increased the paretic plantar flexor effort from 73.7% to 86.6% (p = 0.007). CONCLUSION A more symmetrical gait increases paretic plantar flexor efforts. Individuals post-stroke presenting high plantar flexor efforts when walking have limited muscle capacity to increase non-paretic step after split-belt walking.