SPLIT-BELT TREADMILL ADAPTATION and GAIT SYMMETRY POST-STROKE.

Abstract

Purpose/Hypothesis: The purpose of this study is to understand the capacity of persons with post-stroke hemiparesis to adapt locomotor inter-limb coordination and the influence of this on gait symmetry. Number of Subjects: 8 subjects with chronic post-stroke hemiparesis and age-matched controls have been tested to date. Materials/Methods: Subjects walked on a custom split-belt treadmill (Woodway) where the speed of each belt (leg) could be controlled independently. Subjects walked in baseline conditions (belts tied, slow=0.5 m/s and fast=1.0 m/s), split-belt conditions (impaired leg moving fast (1.0 m/s) in one session, slow (0.5 m/s) in another) and post-adaptation conditions (belts tied, slow=0.5 m/s). OPTOTRAK (Northern Digital, Waterloo ON) sensors were used to record 3-dimensional position data from both sides of the body. Infrared emitting diodes (IREDs) were placed bilaterally on the 5th metatarsal head, lateral malleolus, lateral knee joint space, greater trochanter, iliac crest and acromion process. Foot contacts were determined using foot switches. Intra-limb (i.e. those measured from a single leg: stride length, stance/swing time) and inter-limb (i.e. those where the measurement depended on both legs: time in double support, step length, limb orientation at weight transfer, limb phasing) kinematic variables were calculated. Results: Both controls and people with chronic stroke could adapt inter-limb coordination and showed aftereffects following split-belt practice. Subjects with hemiparesis changed limb phasing and step length from the baseline period to the early adaptation period (p < 0.05, p=0.10, respectively) and stored an after-effect (comparing baseline and early post-adaptation periods, p=0.09, p < 0.05, respectively). Similar results were found for double support and limb orientation at weight transfer, though individual stroke subjects varied in their adaptive abilities. Intra-limb parameters changed rapidly for controls and people with hemiparesis, with no difference between the groups. For the 6 out of 8 subjects with hemiparesis that demonstrated a gait asymmetry, walking on the split-belt treadmill temporarily reduced or eliminated the asymmetry either during split-belt adaptation or due to after-effects in the post-adaptation period. Conclusions: Since all subjects showed some adaptive ability, we suggest that this form of locomotor adaptation may be less dependent on cerebral structures. We speculate that the adaptation and expression of the after-effect may be influenced by several factors including: the degree of locomotor impairment, lesion location, and/or which leg is driven faster during the adaptation. Clinical Relevance: The results of this study preliminarily suggest that persons with post-stroke hemiparesis retain the capability to adapt inter-limb coordination to produce a more symmetric locomotor pattern. Split-belt treadmill training may therefore be useful to improve gait symmetry of people with certain types of stroke.