Counteracting postural perturbations through body weight shift: A pilot study using a robotic platform in subjects with Parkinson's disease

Abnormalities of body-weight transfer occur during several motor tasks in people with Parkinson's disease (PwPD). In this paper, a novel robotic paradigm for assessment and training of dynamic balance was developed and applied to twelve healthy subjects (HS) and ten PwPD to verify its feasibility and to assess the capability of PwPD to counteract the postural perturbations through body-weight shifts. At variance with other robotic paradigms, subjects had to react as fast as possible to the perturbation, bringing the platform back to the horizontal and keeping it until the end of the task. Four randomized perturbations, obtained varying the platform equilibrium angle from 0 to +/- 6 degrees in sagittal (backward, forward) and frontal (right, left) planes, were repeated 3 times. Compared to HS, PwPD showed, in all perturbation directions, increased delay in counteraction phase onset (p <= 0.01), prolonged time to stabilize the platform (p <= 0.02), and higher deviation of the final plate inclination from the horizontal (p <= 0.04), the deviation being larger during sagittal perturbations. PwPD also showed a larger (p = 0.01) postural sway around the stabilization angle following the frontal perturbations. Results are in keeping with the known hypo- and bradykinesia as well as the proprioceptive and kinesthetic impairments in PD. We suggest that the proposed approach is feasible and might be included in balance evaluation and training in PD.