Freezing of gait is a debilitating symptom affecting individuals with Parkinson's disease. Emerging evidence suggests freezing may represent a global motor control deficit beyond gait. We investigated freezing episodes in the upper limbs using spatially-constrained reaching tasks known to elicit freezing of gait. Fourteen people with Parkinson's disease and 13 controls completed reaching tasks under three spatial conditions with varying backgrounds. The tunnel condition produced the greatest kinematic disruptions. Despite people with Parkinson's disease showing significantly longer movement times and slower speeds, they were less accurate in their movements, suggesting observed differences reflect genuine motor control deficits rather than speed-accuracy trade-offs. The tunnel's narrow spatial constraints challenge the motor system's ability to maintain coordinated movement trajectories, with people with Parkinson's disease exhibiting increased trajectory variability. These findings demonstrate that freezing-like episodes extend beyond gait, supporting the hypothesis that freezing represents a global motor phenomenon in Parkinson's disease.
Author Keywords: freezing of gait, motor control, Parkinson's disease, reaching, upper limbs