Influence of obstacle color on locomotor and gaze behaviors during obstacle avoidance in people with Parkinson's disease.

The color of an obstacle may enable a more detailed view of the environment to facilitate obstacle avoidance. However, people with Parkinson's disease (PD) present visual contrast and color detection dysfunction, which could affect obstacle avoidance according to obstacle color. Thus, the aim of this study was to investigate the influence of obstacle color on locomotor and gaze behavior during obstacle avoidance in people with PD and neurologically healthy older individuals. Thirteen people with PD and eleven matched-control group individuals, with normal visual acuity (20/20 on the Snellen chart), performed 20 trials (5 trials for each obstacle color condition) of the obstacle avoidance task with the following obstacle colors: white, black, red, and blue. Participants were positioned at the beginning of a walkway with their eyes closed and, after the start command, opened their eyes, started walking at their preferred velocity, and crossed the obstacle. Spatial-temporal parameters and fixations on the obstacle (gaze behavior) were measured using a three-dimensional camera system and mobile eye-tracker, respectively. Our main findings were the absence of significant color interaction on locomotor and gaze behaviors, the absence of significant main effect of color on gaze behavior, and an effect of obstacle color on locomotor behavior, specifically in the placement of the heel from the obstacle after crossing and toe-clearance for both trailing and leading limbs, which indicates that obstacle color can play a role in obstacle avoidance during walking. However, there was no consistent obstacle color that influenced the locomotor behavior. Therefore, the conclusion of this study is that obstacle color seems to affect locomotor behavior, but not gaze behavior, during walking with obstacle avoidance in people with PD and neurologically healthy individuals. However, no particular obstacle color causes a consistent effect on locomotor behavior.

A multiple domain postural control assessment in people with Parkinson's disease: traditional, non-linear, and rambling and trembling trajectories analysis.

BACKGROUND: Postural impairment is one of the most debilitating symptoms in people with Parkinson's disease (PD), which show faster and more variable oscillation during quiet stance than neurologically healthy individuals. Despite the center of pressure parameters can characterize PD's body sway, they are limited to uncover underlying mechanisms of postural stability and instability. RESEARCH QUESTION: Do a multiple domain analysis, including postural adaptability and rambling and trembling components, explain underlying postural stability and instability mechanisms in people with PD? METHOD: Twenty-four individuals (12 people with PD and 12 neurologically healthy peers) performed three 60-s trials of upright quiet standing on a force platform. Traditional and non-linear parameters (Detrended Fluctuation Analysis- DFA and Multiscale Entropy- MSE) and rambling and trembling trajectories were calculated for anterior-posterior (AP) and medial-lateral (ML) directions. RESULTS: PDG's postural control was worse compared to CG, displaying longer displacement, higher velocity, and RMS. Univariate analyses revealed largely longer displacement and RMS only for the AP direction and largely higher velocity for both AP and ML directions. Also, PD individuals showed lower AP complexity, higher AP and ML DFA, and increased AP and ML displacement, velocity, and RMS of rambling and trembling components compared to neurologically healthy individuals. SIGNIFICANCE: Based upon these results, people with PD have a lower capacity to adapt posture and impaired both rambling and trembling components compared to neurologically healthy individuals. These findings provide new insights to explain the larger, faster, and more variable sway in people with PD.

Prolonged Standing Task Affects Adaptability of Postural Control in People With Parkinson's Disease.

BACKGROUND: Studies on short-term upright quiet standing tasks have presented contradictory findings about postural control in people with Parkinson's disease (pwPD). Prolonged trial durations might better depict body sway and discriminate pwPD and controls. OBJECTIVE: The aim of this study was to investigate postural control in pwPD during a prolonged standing task. METHODS: A total of 26 pwPD and 25 neurologically healthy individuals performed 3 quiet standing trials (60 s) before completing a constrained prolonged standing task for 15 minutes. Motion capture was used to record body sway (Vicon, 100 Hz). To investigate the body sway behavior during the 15 minutes of standing, the analysis was divided into three 5-minute-long phases: early, middle, and late. The following body sway parameters were calculated for the anterior-posterior (AP) and medial-lateral (ML) directions: velocity, root-mean-square, and detrended fluctuations analysis (DFA). The body sway area was also calculated. Two-way ANOVAs (group and phases) and 1-way ANOVA (group) were used to compare these parameters for the prolonged standing and quiet standing, respectively. RESULTS: pwPD presented smaller sway area (P < .001), less complexity (DFA; AP: P < .009; ML: P < .01), and faster velocity (AP: P < .002; ML: P < .001) of body sway compared with the control group during the prolonged standing task. Although the groups swayed similarly (no difference for sway area) during quiet standing, they presented differences in sway area during the prolonged standing task (P < .001). CONCLUSIONS: Prolonged standing task reduced adaptability of the postural control system in pwPD. In addition, the prolonged standing task may better analyze the adaptability of the postural control system in pwPD.

High-Intensity Interval Versus Moderate-Intensity Continuous Training in Individuals With Parkinson's Disease: Hemodynamic and Functional Adaptation.

PURPOSE: To investigate the effect of high-intensity interval training (HIIT) versus moderate-intensity continuous exercise training (MICE) on hemodynamic and functional variables in individuals with Parkinson's disease. METHODS: Twenty participants (13 men) were randomly assigned to a thrice-weekly HIIT (n = 12) or MICE (n = 8) for 12 weeks. Hemodynamic (resting heart rate and blood pressure, carotid femoral pulse wave velocity, endothelial reactivity, and heart rate variability) and functional variables (5-time sit-to-stand, timed up and go, and 6-min walking tests) assessed before and after training. RESULTS: Demographic, hemodynamic and functional variables were similar between groups at baseline. Endothelial reactivity tended to increase after HIIT, but not after MICE, resulting in improved level (∼8%, P < .01) of this variable in HIIT versus MICE during follow-up. Six-minute walking test improved after HIIT (10.4 ± 3.8%, P < .05), but did not change after MICE. Sit to stand improved similarly after HIIT (27.2 ± 6.1%, P < .05) and MICE (21.5 ± 5.4%, P < .05). No significant changes were found after HIIT or MICE in any other variable assessed. CONCLUSION: These results suggest that exercise intensity may influence training-induced adaptation on endothelial reactivity and aerobic capacity in individuals with Parkinson's disease.

Parkinson's patients delay fixations when circumventing an obstacle and performing a dual cognitive task.

BACKGROUND: People with Parkinson's disease (PD) do not differ from neurologically healthy individuals in obstacle circumvention during walking, therefore they are able to use visual feedback adequately to control motor behavior in this task. However, individuals are often distracted by the secondary task when circumventing an obstacle. An increased cognitive load can require prolonged gaze fixation time on a location of interest to compensate for longer information processing duration. RESEARCH QUESTION: To investigate the effects of cognitive dual tasking (DT) on gaze behavior during waking with obstacle circumvention in people with PD and control group, and to determine the impact of gaze behavior on motor strategy. METHODS: Fifteen individuals with PD (PD-group) and 15 neurologically healthy individuals walked at a self-selected speed over a walkway and circumvented an obstacle centered in the walkway. The experimental conditions (5 trials each one) included obstacle circumvention without DT (OC) and obstacle circumvention with DT (OCDT). In the cognitive task, the participant mentally counted the number of times a target number appeared in an audio recording. We analyzed gaze behavior (i.e. number of gaze fixations and duration on the ground and obstacle), standard gait measures and DT cost. Two-way ANOVAs were completed for gait parameters and moment of fixation. RESULTS: There was no significant difference in DT cost between groups and no obstacle contacts. The participants performed a longer mean duration of fixations on the ground during OCDT compared to OC. Group x condition interactions indicated that the PD-group delayed the obstacle fixation relative to the NHI for OCDT (p < 0.001) and presented greater medial-lateral body clearance (p < 0.001) and longer double support time (p < 0.001) during OCDT compared to OC. SIGNIFICANCE: The results of this study suggest that deficits in locomotion during DT in PD-group may be caused, at least in part, by a reduced ability to fixate gaze at appropriate times during walking.

Obstacle circumvention and eye coordination during walking to least and most affected side in people with Parkinson's disease.

BACKGROUND: The mechanisms that contribute to gait asymmetry in people with Parkinson's disease (PD) are unclear, mainly during gait with greater environmental demand, such as when an obstacle is circumvented while walking. OBJECTIVE: The aim of this study was to investigate the effects of obstacle circumvention of the least and most affected side on motor and gaze behavior in people with PD under/without the effects of dopaminergic medication. METHODS: Fifteen people with PD and 15 matched-control individuals were instructed to walk along a pathway, at a self-selected velocity, and to circumvent an obstacle, avoiding contact with it. Each participant performed five trials for each side. Kinematic parameters, mediolateral and horizontal body clearance to the obstacle, strategy to circumvent the obstacle, and gaze behavior were calculated. Parameters were grouped according to the side that the obstacle was circumvented and compared by three-way ANOVAs. RESULTS: Both people with PD and the control group presented asymmetry to circumvent an obstacle during walking, however this was exacerbated in people with PD. Individuals with PD presented safe strategies (largest mediolateral and horizontal body clearance to the obstacle, "lead-out" strategy, and higher number and time of fixations on the obstacle) during obstacle circumvention for the least affected side compared to the most affected side. In addition, positive effects of dopaminergic medication on body clearance, spatial-temporal parameters, and gaze behavior were evidenced only when the obstacle was circumvented to the least affected side. CONCLUSIONS: The obstacle circumvention to the most affected side is risky for people with PD.