Use of the Gait Deviation Index and spatiotemporal variables for the assessment of dual task interference paradigm.

Three-dimensional gait analysis (3DGA) is an important element in the quantitative evaluation of gait in subjects with Parkinson's disease (PD). Indexes, such as the Gait Deviation Index (GDI), have recently been proposed as a summary measure of gait. The aim of the present study was to investigate the effectiveness of the GDI and spatiotemporal variables in the quantification of changes in gait during a dual-task (DT) exercise. Fourteen patients with idiopathic PD and nine healthy subjects (CG) participated in the study. All subjects walked under two conditions: free walking and DT walking. The GDI was computed from the 3DGA data. The results show gait impairment during DT, a significant difference between groups regarding GDI and an interaction effect involving the group, side and task factors. The CG and PDG were different independent of interference and side, but interference was only different for the PDG group. The results also demonstrate that the GDI should be an appropriate outcome measure for the evaluation of the effects of DT on patients with Parkinson's disease.