Analysis of stroke patient walking dynamics using a tri-axial accelerometer.

The purpose of this study was to describe the characteristics of stroke patient gait using the acceleration signals which were obtained during walking. Sixty-three stroke hemiplegic patients and 21 age-matched healthy elderly individuals took part in this study. A wireless tri-axial accelerometer, fixed to a belt at the level of the L3 spinous process, was used to measure trunk acceleration. Subjects were instructed to walk at a self-selected, comfortable walking speed. The acceleration signal was sampled at the rate of 200 Hz. Gait parameters and functional recovery tests were also evaluated. We analyzed the correlation between the gait parameters, functional recovery and acceleration. Acceleration was utilized as the root mean square (RMS), normalized RMS by velocity and average step length, as a measure of gait smoothness, and autocorrelation (AC) as a measure of stride similarity and regularity. The raw RMS and AC values of the stroke were significantly lower than the matched healthy elderly (p<0.01) in all axes. In contrast, the stroke patients' normalized RMS values were higher than the controls (p<0.05) in all axes. These results suggest that accelerometry gait parameters can discriminate between the stroke patients and the control group. The values of normalized RMS correlated with the smoothness or dynamics of the walking pattern, which reflects motor recovery and gait abilities. This study suggests that normalized RMS of accelerometer recordings from the trunk is valid in objectively measuring walking movements as an index of treatment outcome for patients in rehabilitation.