Challenging context affects standing reach kinematics among Parkinson's disease patients.

The standing reach movement requires coordinated activation of postural and focal motor responses. For PD patients, both components of this reaching task exhibit evidence of motor deficit. In the present experiment, we examined these motor responses during a standing reaching task in a challenging environmental context. PD patients (n=10) and control participants (n=8) were asked to reach and drink from a glass while standing on a raised platform (0.6m) with and without an additional anterior platform. Removal of the anterior platform placed participants in a higher postural threat context. Displacement data were captured from markers on relevant body landmarks to provide reach end-point and whole-body movement kinematics. Our results showed that PD patients delayed trunk flexion and peak end-point velocity during the forward reach phase and peak centre of mass velocity during the transport phase for a challenged standing reach. These behaviours, in combination with the bradykinetic motor control observed in PD patients, could contribute to the frequent falls observed among the PD population.