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BACKGROUND: Turning is the most important trigger for freezing of gait (FOG) in Parkinson's disease (PD), and dual-tasking has been suggested to influence FOG as well. OBJECTIVE: To understand the effects of dual tasking and turning on FOG. METHODS: 14 Freezers and 14 non-freezers matched for disease severity and 14 age-matched controls were asked to turn 180° and 360° with and without a cognitive dual-task during the off-period of the medication cycle. Total number of steps, duration, cadence, freezing-frequency, and secondary-task performance were measured. RESULTS: Seven freezers froze during the protocol. Freezing occurred in 37.5% of trials during 180° turning compared to 0% during straight-line walking (X(2) = 10.44, p < 0.01). The occurrence of FOG increased during 360° when also a dual-task was added (X(2) = 4.23, p = 0.04). Freezers took significantly more steps and were slower than controls in all conditions. The presence of a dual-task increased these differences. Cadence increased significantly for freezers during 360° and 180° compared to straight-line walking. In contrast, cadence was decreased during turning in controls and non-freezers. During straight-line walking, only freezers made errors in the secondary task. Controls increased their error-rate during 180° turning, whereas freezers deteriorated their secondary task performance during 360°. CONCLUSIONS: 360° turning in combination with a dual-task is the most important trigger for freezing. During turning, non-freezers and controls decreased their cadence whereas freezers increased it, which may be related to FOG. Freezers adopted a posture second strategy in contrast to non-freezers when confronted with a dual task.
Spildooren et al. (Wed,) studied this question.