Locomotor asymmetry in post-stroke individuals: Why and how to use the split-belt treadmill to improve the gait performance

Abstract

The recovery of gait symmetry post-stroke tends to be more challenging compared to other functional deficits when using conventional therapy. However, investigations on walking at unequal speeds on a split-belt treadmill have revealed improvements in symmetry of spatial and temporal gait parameters. The main objective of this study was to identify the causes of changes in spatio-temporal parameters by quantifying net joint moments and muscular levels of effort in the lower limbs during different walking conditions on a split-belt treadmill. Twenty individuals with chronic stroke and a mean age of 49 (± 13) years and 10 age-matched controls walked on an instrumented split-belt treadmill under three gait periods: (1) baseline (tied-belt); (2) adaptation (split-belt); and (3) post-adaptation (tied-belt). Participants post-stroke performed the protocol with the paretic and non-paretic leg on the faster belt when belts were split. Kinematic data were recorded with the Optotrak system and ground reaction forces were collected via the instrumented split-belt treadmill. The dynamic inverse gave the joint moments while levels of effort were assessed with the muscular utilization ratio (ratio of walking moment relative to the muscle's maximal capability). Repeated measures ANOVA and t -tests were used to compare the variables during the three periods. Pearson correlations were used to assess the relationships between asymmetries in these parameters. The condition with the shorter step on the fast belt improved the step length symmetry. Placing the paretic limb on the slow belt increased the plantar flexion moment in post-adaptation and that such increase was correlated with the increase in controlateral step length. A more symmetrical gait pattern (temporal or spatial) following walking on the split-belt treadmill required high levels of effort (over 85%) in paretic plantar flexors. Results also revealed that healthy individuals and patients had different ability to detect asymmetry. These results suggest that muscle strength and muscular level of effort, mainly in paretic plantar flexors, need to be considered to use the split-belt treadmill in the adaptation (split-belt) period. The classification of patients into subgroups according to their sensorimotor deficits and gait asymmetries is an important aspect to consider with this type of training.