title: Reformulation in the phase plane enhances smoothness rater accuracy in stroke.
abstract: To improve the characterization of motor impairment, we compared the sensitivities of a phase plane metric with temporal domain measures derived from integrated squared jerk (ISJ). Five subjects with stroke and a cohort of 21 neurologically intact volunteers performed self-paced, isolated elbow flexions. Analysis of angular trajectories from the stroke group revealed that temporal domain metrics failed to detect a performance deficit at the p < .05 level, while the phase plane metric did resolve a deficit (p < .01). When applied to a subset of movements with arrest periods, the phase measure also uniquely identified impairment (Wilcoxon rank-sum test, p < .001). Finally, when tested on a data-driven model, the phase measure, but not temporal metrics, increased monotonically with the severity of trajectory distortions. We conclude that motion smoothness can be accurately measured in the phase plane.
authors.affiliation: National Institute of Mental Health, Clinical Disorders Branch, Building 10, Room 4N313D, Neuropathology Section, Bethesda, MD 20892, USA. Michael.Wininger@nih.gov
authors.forename: Michael
authors.initials: M
authors.lastname: Wininger
authors.forename: Nam H
authors.initials: NH
authors.lastname: Kim
authors.forename: William
authors.initials: W
authors.lastname: Craelius
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology*; D016022:Case-Control Studies; D004550:Elbow / Q000503:physiopathology*; D004551:Elbow Joint / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009068:Movement / Q000502:physiology*; D020521:Stroke / Q000503:physiopathology*