Whole-body coordination when turning on-the-spot in people with stroke and Parkinson's disease: a comparison with healthy controls

Abstract

Turning around to interact with the environment is a common activity of daily living. The location of a target for interaction may be known or unknown prior to turning and the angle of a turn may vary depending on the task to be carried out. Stroke and Parkinson’s disease could compromise coordination of body movement during turning which may pose a risk for instability and subsequent falls. The sequence of onset latency, peak velocity and timing of peak velocity of body segments (eye, head, shoulder, pelvis and foot) while turning on-the-spot were investigated in people with stroke and age-matched healthy controls (study 1) and in people with Parkinson’s disease and age-matched healthy controls (study 2). The effect of target predictability, turn angle and turn direction on the sequence of the movement of the body segments were also investigated. Participants were asked to stand in front of a light and either turn to a specific light (predictable condition) or locate and turn to a random light (unpredictable condition) placed at 45°, 90° or 135° to the right or left when the light in front extinguished.

The results showed that the people with stroke and Parkinson’s disease (PD) initiated the movement of the segments later, had lower peak velocities and attained the peak velocities later than their control counterparts. People with PD showed more simultaneous onset of rotation of body segments as compared to their age-matched control when turning to 135°. The sequence of onset of rotation of the body segments was similar between the people with PD and their age-matched controls for all the other turning tasks. People with stroke also had comparable sequence of onset of rotation of body segments with their age-matched controls for all the turning tasks. While people with stroke presented with consistent pattern of peak velocity of the body segments for all the turning tasks, their control counterparts showed differences in the pattern of the peak velocities when turning to dominant and non-dominant sides. People with PD showed similar peak velocities of pelvis and foot when turning 45° to initially affected side as compared to separate peak velocities of the pelvis and foot in the stroke and control groups. The peak velocities of the segments (head, shoulder, pelvis and foot) occurred at more or less the same time for most of the turning tasks.

Impairment of the relative movement of body segments during functional tasks could challenge the balance of an individual. The sequence of movement of body segments in the different tasks could therefore be related to balance during turning to identify which of the strategies of turning could present with risk of falls. Predictability of a target, turn angle and turn direction should be considered when developing interventions to avoid falls during turning and strategies for improving speed of reacting to perturbations should be developed for people with stroke and Parkinson’s disease.

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