title: Increased force variability in chronic stroke: contributions of force modulation below 1 Hz.
abstract: Increased force variability constitutes a hallmark of arm disabilities following stroke. Force variability is related to the modulation of force below 1 Hz in healthy young and older adults. However, whether the increased force variability observed post stroke is related to the modulation of force below 1 Hz remains unknown. Thus, the purpose of this study was to compare force modulation below 1 Hz in chronic stroke and age-matched healthy individuals. Both stroke and control individuals (N = 26) performed an isometric grip task to submaximal force levels. Coefficient of variation quantified force variability, and power spectrum density of force quantified force modulation below 1 Hz with a high resolution (0.07 Hz). Analyses indicated that force variability was greater for the stroke group compared with to healthy controls and for the paretic hand compared with the non-paretic hand. Force modulation below 1 Hz differentiated the stroke individuals and healthy controls, as well as the paretic and non-paretic hands. Specifically, stroke individuals (paretic hand) exhibited greater power ~0.2 Hz (0.07-0.35 Hz) and lesser power ~0.6 Hz (0.49-0.77 Hz) compared to healthy controls (non-dominant hand). Similarly, the paretic hand exhibited greater power ~0.2 Hz, and lesser power ~0.6 Hz than the non-paretic hand. Moreover, variability of force was strongly predicted from the modulation of specific frequencies below 1 Hz (R(2) = 0.80). Together, these findings indicate that the modulation of force below 1 Hz provides significant insight into changes in motor control after stroke.
authors.affiliation: Department of Applied Physiology and Kinesiology, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America ; Brain Rehabilitation Research Center of Excellence, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Neha
authors.initials: N
authors.lastname: Lodha
authors.affiliation: Department of Applied Physiology and Kinesiology, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Misra
authors.affiliation: Department of Applied Physiology and Kinesiology, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Coombes
authors.affiliation: Department of Applied Physiology and Kinesiology, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America ; Department of Physical Therapy, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Evangelos A
authors.initials: EA
authors.lastname: Christou
authors.affiliation: Department of Applied Physiology and Kinesiology, Malcom Randall VA Medical Center, University of Florida, Gainesville, Florida, United States of America.
authors.forename: James H
authors.initials: JH
authors.lastname: Cauraugh
mesh_terms: D000368:Aged; D002908:Chronic Disease; D005260:Female; D007839:Functional Laterality; D006225:Hand / Q000503:physiopathology; D018737:Hand Strength; D006801:Humans; D007537:Isometric Contraction; D008297:Male; D008875:Middle Aged; D020521:Stroke / Q000503:physiopathology*; D000071939:Stroke Rehabilitation