Sudden turn during walking is impaired in people with Parkinson's disease.

The present study compared kinematic strategies for making sudden directional changes during walking between patients with Parkinson's disease (PwPD) and age-matched controls. Ten PwPD and 10 healthy elderly were visually cued to walk straight or to turn either 30 degrees or 60 degrees to the left or right, at the mid-point of a 9-m walkway. Three-dimensional kinematic data recorded: (1) the onset time of body segments in response to the turning cue, and (2) step width at the first ipsilateral foot contact (IFC(1)) marking the beginning of turn, the subsequent contralateral foot contact (CFC), and the second ipsilateral foot contact (IFC(2)) marking the completion of turn. For both 30 degrees and 60 degrees turns, PwPD had later onset times for lateral foot displacement, and larger time lags between the onset of body CoM and the lateral foot translation than healthy subjects (P < 0.05). Furthermore, PwPD had a significantly narrower step width than healthy subjects (P < 0.05). Despite these differences, PwPD and control subjects scaled up turning speed and amplitude similarly for 30 degrees and 60 degrees turns. Our findings suggested that PwPD manifested specific difficulty in modifying their ongoing motor program to switch their locomotion from straight line to sideway direction, but their ability to scale movement speed and amplitude appeared to be preserved.