Test-retest reliability of stride length-cadence gait relationship in Parkinson's disease

Introduction: The gait pattern in Parkinson's disease (PD) subjects is characterized by a specific deficit of the internal regulation of the stride length (SL), while the control of the cadence (Cad) remains intact. The purpose of the present study was to evaluate the reliability of the stride length-cadence relationship (SLCrel) in a group of PD subjects. Methods: Thirty five PD subjects performed two sessions, separated by a three month resting period. In each session Gait speed, SL and Cad were evaluated at five different self-selected speed conditions: preferred, slow, very slow, fast and very fast. Linear regression analysis was used to explore the SLCrel and to determine the slope, intercept and coefficient of determination (R-2) for each participant. Test-retest reliability for the slope and intercept was calculated using intra-class correlation coefficient (ICC), 95% confidence interval (CI), and standard error of mean (SEM). Results: There were no significant differences in the slope and intercept between the two sessions. The overall speed was significantly faster in the second session compared with the first one (F = 4.60, p = 0.03). The SLCrel showed high reliability across the sessions (ICC = 0.89 and ICC = 0.91; 95% CI = 0.80 - 0.95 and 95% CI = 0.82 - 0.95; SEM = 0.002 and SEM = 0.073, for the slope and interception, respectively). Conclusions: The SLCrel in Parkinsonian gait is a reproducible measure across a period of three months, and may be a useful tool to explore the specificity of gait rehabilitation interventions in PD subjects.