Alterations in Gait Initiation of subjects with Parkinson’s Disease: a comparative study with matched healthy controls

Objective: To compare spatiotemporal, kinetic and kinematic variables of Gait Initiation (GI) between individuals with Parkinson’s disease (PD) and healthy controls (HC). Background: Balance and postural control impairments are cardinal symptoms of PD[1], affecting both walking and fall risk[ 2,3].Walking is an automatic task that begins with the volitional “first step”.GI involves transitioning from bipodal to single-leg support to execute the “first step”[4].Individuals with PD exhibit altered spatiotemporal parameters of the center of pressure (COP) during this transition[5],compared to healthy subjects which may impact kinetic and kinematic parameters of the “first step”. Method: While standing on a force plate, participants began walking upon a visual cue. The first step was recorded on a second, contiguous force plate. Each subject performed three repetitions per leg, recorded using a motion capture system with 10 infra-red cameras (Qualisys). Continuous-time variables (Ground Reaction Forces-GRFs) were compared between groups using Statistical Parametric Mapping (MATLAB). The range of motion of lower limb joints at heel strike (discrete-time variable) and COP parameters (length, timing and velocity) were compared with t-test or U Mann-Withney depending on data distribution. Results: Ten individuals with PD(age:60.6±7.3 years;H&Y:2) and ten matched HC(age:61.8±7.4 years) participated in the study. A significant increase in knee flexion (PD:12.3°±3.6vs. HC:8.0°±3.1; MD[Mean difference]:4.3°, p<0.001; 95%CI:-6.1 to -2.5) and ankle dorsiflexion (PD: 2.2°±5.8vs. HC: 0.03°±2.9; MD: 2.16°, p=0.01; 95%CI: -3.7 to -0.5) was observed in the PD group at heel contact of the first step. Regarding vertical GRF during the stance phase, the PD group exhibited a delayed passive first peak and a reduction in the subsequent active peak (p<0.05; Figure 1). Additionally, PD participants demonstrated reduced braking force and an early transition to a propulsive force, as indicated by antero-posterior GRF analysis (p<0.05; Figure 2). No other significant between-group differences were observed. Conclusion: This study highlights differences in GI between individuals PD and HC, primarily in relation to GRFs which may serve as measures for assessing balance impairments in Parkinsonian gait. Further studies are needed to better understand their potential relationships with other kinetic and kinematic parameters.