Variability in spatiotemporal step characteristics and its relationship to walking performance post-stroke

Abstract

Gait variability is suggested to be a quantifiable measure to evaluate mobility impairments. However, it is unknown whether gait variability could be used as a marker of impaired walking performance post-stroke. Therefore, the purpose of this study was to determine whether gait variability measures could be used as walking performance measures post-stroke. Hemiparetic variability was compared to healthy gait variability and associated to clinical assessments that evaluate impaired performance post-stroke. Spatiotemporal characteristics were collected from 94 persons with post-stroke hemiparesis and 22 similarly aged healthy persons as they walked over an instrumented mat. Gait variability was calculated as the standard deviation in step lengths, stride widths, pre-swing, swing and stride times. Hemiparetic performance was evaluated using lower-extremity Fugl-Meyer grading, dynamic gait index scale (available in population sub-sets) and an asymmetry index. Results revealed that variability increased in step length, swing, pre-swing and stride times (p<.001) during hemiparetic walking as compared to healthy gait. Paretic leg swing time variability was increased compared to the non-paretic during hemiparetic walking (p<.001). Between-leg differences in variability for other spatiotemporal characteristics were revealed in participants with the most impaired performance. Further, increased step variability and reduced width variability related to poor performance outcomes (severe hemiparesis, asymmetrical gait and poor balance). Patterns of gait variability were evident within sub-groups of the hemiparetic population. Results of this study suggest that between-leg differences in swing and pre-swing time variability, increased step length and stride time variability and decreased width variability are quantifiable markers of impaired walking performance poststroke.

Figures

Figure 1. Differences in Temporal variability between healthy (n = 22) and participants with hemiparesis (n = 94) at Self-selected (SS) walking speeds

The box plots indicate the range in the data. The central horizontal line is the median of the sample. The length of the box indicates the inter-quartile range with the upper and lower boundaries of the box indicating the upper and lower quartile, respectively. Circles represent sample values that statistically indicate outlier or extreme values (by SPSS software). In impaired populations, these outlier values are true indicators of behavior and represent those persons showing excessive variability. * indicates statistically significant differences from healthy leg at p

Figure 2. Differences in Spatial variability between healthy (n = 22) and participants with hemiparesis (n = 94) at Self-selected (SS) walking speeds

The box plots indicate the range in the data similar to Figure1. * indicates statistically significant differences from healthy leg at p

Figure 3. Differences in Temporal variability in hemiparetic participants based on their performance on clinical assessments

The box plots indicate the range in the data similar to Figures 1. Blue represents paretic leg and Green represents non-paretic leg for swing time and pre-swing time variability. In general, poor performance is indicated by more severe hemiparesis (lower LE-FM scores), asymmetrical gait (longer or shorter paretic steps) and poorer balance performance (lower DGI scores)]. Note the between-leg differences in swing and pre-swing time in persons with moderate and severe hemiparesis, those walking asymmetrically and in persons showing poor balance performance. Note that while stride time variability differences were observed in sub-groups of the hemiparetic population, these have not been represented in the Figure.

Figure 4. Differences in Spatial variability in hemiparetic participants based on their performance on clinical assessments

The box plots indicate the range in the data similar to Figures 1. Blue represents paretic leg and Green represents non-paretic leg for step length variability. Note that stride width variability does not show a consistent trend to differ across the different sub-groups of the hemiparetic population.