Time dependency of walking classification in stroke.

BACKGROUND AND PURPOSE To facilitate optimal stroke rehabilitation, valid interpretation of observed functional recovery is required. The purpose of this study was to examine the longitudinal relationship between comfortable walking speed and Functional Ambulation Categories (FAC) scores for physically independent gait. SUBJECTS This study was a prospective cohort study with 73 subjects who were severely affected by acute stroke. METHODS Functional Ambulation Categories classification and walking speed were measured between weeks 4 and 26 after stroke. The responsiveness of walking speed measurements for detecting clinically important speed changes was determined, and the longitudinal association between walking speed and FAC scores and its time dependency were established. This relationship subsequently was scrutinized for possible speed changes occurring within specific FAC scores. Responsiveness ratios, random coefficient analysis, paired Student t tests, and the Cohen kappa statistic were used for statistical analyses. RESULTS Responsiveness ratios exceeded the smallest detectable differences. Random coefficient analysis demonstrated a significant between- and within-subject coefficient and a significant negative interaction between timing of measurements and FAC scores. Paired Student t tests revealed mostly significant pretest-posttest differences in walking speeds, and all kappa values for pretest-posttest FAC scores were significant. DISCUSSION AND CONCLUSION Walking speed measurements are sensitive for detecting clinically important changes. Functional Ambulation Categories scores are dependent on the timing of comfortable walking speed measurements after stroke. Moreover, there are indications that, in this relationship, repeated FAC appraisals are not only based on steady walking speeds, but that the walking speeds related to a specific FAC appraisal also change and, over time, may shift gradually from higher to lower speeds.