title: The effects of predictability on inter-limb postural synchronization prior to bouts of postural instability.
abstract: Anticipatory balance control optimizes balance reactions to postural perturbations. Predictive control is dependent on the ability of the central nervous system to modulate gain in accordance with specific task demands. Inter-limb synchronization is a sensitive measure of individual limb contributions to balance control and may reflect the coordination of gain modulation in preparation for instability. The purpose of the study was to determine whether gain modulation in advance of predictable bouts of instability was reflected in the extent of inter-limb synchronization. Two adjacent force plates were used to collect center of pressure (COP) data from 12 healthy young adults (27.5±3.4 years). Participants prepared for internal and external balance perturbations using a cueing paradigm with three auditory warning tones followed by an imperative tone. Perturbations were delivered in blocked and randomized conditions with two perturbation magnitudes (small and large). Inter-limb synchrony was calculated using the cross-correlation function of the COP excursions from the left and right foot for three seconds prior to perturbation onset in the anteroposterior (AP) and mediolateral (ML) direction. Inter-limb synchrony decreased in the AP and ML directions as perturbation magnitude became more unpredictable. The need to take a step or not knowing whether a step was required prior to postural instability reduced ML inter-limb synchrony. No differences were found between internal and external perturbations. Modulation of postural set was evident in the extent of inter-limb synchrony.
authors.affiliation: University of Toronto, Rehabilitation Sciences Institute, 500 University Avenue, Toronto, ON M5G 1V7, Canada; Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada; Toronto Rehabilitation Institute, 550 University Avenue, Toronto, ON M5G 2A2, Canada; Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada.
authors.forename: Olinda
authors.initials: O
authors.lastname: Habib Perez
authors.affiliation: University of Manitoba, Faculty of Kinesiology and Recreation Management, 102 Frank Kennedy Centre, Winnipeg, MB R3T 2N2, Canada.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Singer
authors.affiliation: University of Toronto, Rehabilitation Sciences Institute, 500 University Avenue, Toronto, ON M5G 1V7, Canada; University of Toronto, Department of Physical Therapy, 500 University Avenue, Toronto, ON M5G 1V7, Canada; Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada; Toronto Rehabilitation Institute, 550 University Avenue, Toronto, ON M5G 2A2, Canada; Heart and Stroke Foundation Canadian Partnership for Stroke Recovery, 2075 Bayview Avenue, Toronto, ON M4N 3M5, Canada. Electronic address: george.mochizuki@sunnybrook.ca.
authors.forename: George
authors.initials: G
authors.lastname: Mochizuki
mesh_terms: D000328:Adult; D003463:Cues; D005260:Female; D005528:Foot; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D008297:Male; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D055815:Young Adult
keywords: Balance; Center of pressure; Central set; Coordination; Cross-correlation