Harmonic Ratio is the Most Responsive Trunk-Acceleration Derived Gait Index to Rehabilitation in People with Parkinson’s Disease at Moderate Disease Stages

Background: Harmonic ratios (HRs), recurrence quantification analysis in the antero-posterior direction (RQAdetAP), and stride length coefficient of variation (CV) have recently been shown to characterize gait abnormalities and fall risk in people with Parkinson's disease (pwPD) at moderate disease stages.Research question: This study aimed to i) assess the internal and external responsiveness to rehabilitation of HR, RQAdetAP, and CV, ii) identify the baseline predictors of normalization of the gait stability indexes, and iii) investigate the correlations between the gait indexes modifications (Delta) and clinical and kinematic Delta s in pwPD at Hoehn and Yahr disease staging classification 3.Methods: The trunk acceleration patterns of 21 pwPD and 21 age- and speed-matched healthy subjects (HSmatched) were acquired during gait using an inertial measurement unit at baseline (T0). pwPD were also assessed after a 4-week rehabilitation period (T1). Each participant's HR in the antero-posterior (HRAP), medio-lateral (HRML), and vertical directions, RQAdetAP, CV, spatio-temporal, and kinematic variables were calculated.Results: At T1, HRAP and HRML improved to normative values and showed high internal and external responsiveness. Lower HRs and higher pelvic rotation values at baseline were predictors of Delta HRs. A minimal clinically important difference (MCID) >= 21.5 % is required to normalize HRAP with 95 % probability. MCID >= 36.9 % is required to normalize HRML with 92 % probability. Delta HRAP correlated with Delta HRML and both correlated with Delta stride length and Delta pelvic rotation, regardless of Delta gait speed. RQAdetAP and step length CV were not responsive to rehabilitation.Significance: When using inertial measurement units, HRAP and HRML can be considered as responsive outcome measures for assessing the effectiveness of rehabilitation on trunk smoothness during walking in pwPD at moderate disease stages.