Turning during gait is a complex component of locomotor capacity and can prove challenging to individuals with neurodegenerative diseases during their day-to-day lives. In Parkinson's disease (PD), motor dysfunction can be exacerbated in conditions that require interruptions in gait or change in direction. These changes in gait are among the leading factors contributing to falls and can occur at different stages and in different clinical subtypes of the disease, compromising functionality and, consequently, social participation.

To describe and compare biomechanical variables during the task of turning while walking in individuals with Parkinson's disease and its different clinical subtypes.

A cross-sectional study approved composed of 43 individuals with idiopathic Parkinson's disease, divided into groups according to their clinical subtype: akineto-rigid, tremor-dominant, and mixed. Motor impairment was evaluated using the Unified Parkinson's Disease Rating Scale, and the cognitive status of individuals was assessed using the Mini-Mental State Examination. The biomechanical parameters of gait (number of steps, step length, cadence, as well as variables associated with the displacement of the center of mass, such as amplitude, velocity, and turning radius) were analyzed while turning during gait, in a kinematics laboratory. Statistical analysis included a comparison between Parkinson's disease subtypes (one-way ANOVA and Kruskal-Wallis) and a correlation between biomechanical parameters (Pearson and Spearman), with the significance set at 5%.

There were no statistically significant differences in the comparison between akineto-rigid, tremor-dominant, and the mixed subtypes. The correlation analysis highlighted a significant correlation between the anticipatory step length and the number of steps (r = -0.418; p = 0.005), step length while turning (r = 0.805; p < 0.001), step length after turning (r = 0.644; p < 0.001), the mean velocity (r = 0.830; p < 0.001), the mean velocity while turning (r = 0.755; p < 0.001), and the maximum velocity (rho = 0.835; p < 0.001).

In people with Parkinson's disease, the greater the length of the anticipatory step, the greater the step length required to turn and the greater the step length taken after turning. In addition, the greater the speed, the greater the step length amplitude, and the greater the radius of the turn, resulting in fewer steps in order to complete the task.

This research demonstrates that individuals with Parkinson's disease face difficulties when turning during gait. The results suggest that these difficulties primarily occur during the anticipatory phase of the turn, which affects the entire task. Therefore, these findings can potentially be used to guide rehabilitation interventions in individuals with Parkinson's disease, such as targeting the anticipatory phase of turning through gait training, visual and auditory cues, rhythmic cues, verbal cues, environmental enrichment, and progressive activities with increasing complexity. These interventions are likely to be beneficial in improving turning and gait performance in the day-to-day lives of individuals with Parkinson's disease.