title: Force control and disease severity in Parkinson's disease.
abstract: Several measures of isometric contractions reflect motor impairments in subjects with Parkinson's disease (PD), including long relaxation times and greater power in the 5 to 15 Hz electromyographic (EMG) bandwidth during the holding phase of contractions compared to those measures in healthy subjects. We sought to determine whether the impairments observed in subjects with PD in the performance of isometric contractions reflect disease severity. Twenty-eight subjects with PD performed isometric contractions at a torque level equal to 50% of the torque generated during a maximum voluntary contraction while off medication. Subjects were instructed to reach the target torque as fast as possible upon hearing the auditory "go" signal and to relax their muscles when a second auditory cue signaled the end of the hold phase. There was a significant positive correlation between torque relaxation time and Unified Parkinson's Disease Rating Scale (UPDRS)-Motor score. A significant positive correlation was also observed between the proportion of power in the 5 to 15 Hz frequency bin of the agonist EMG signal and UPDRS-Motor score, and a significant negative correlation between the proportion of power in the 15 to 30 Hz frequency bin and UPDRS-Motor score. These measures provide objective quantification of the severity of motor impairment that can be used to investigate the efficacy of different interventions in individuals with PD.
authors.affiliation: Department of Physical Therapy, School of Health and Rehabilitation Sciences, Indiana University, Indianapolis, Indiana, USA.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Robichaud
authors.affiliation: Department of Movement Sciences (M/C 994), University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Kerstin D
authors.initials: KD
authors.lastname: Pfann
authors.affiliation: Department of Movement Sciences (M/C 994), University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: David E
authors.initials: DE
authors.lastname: Vaillancourt
authors.affiliation: Department of Neurological Sciences, Rush Medical Center, Chicago, Illinois, USA.
authors.forename: Cynthia L
authors.initials: CL
authors.lastname: Comella
authors.affiliation: Department of Movement Sciences (M/C 994), University of Illinois at Chicago, Chicago, Illinois, USA.|Department of Neurological Sciences, Rush Medical Center, Chicago, Illinois, USA.|Department of Physical Therapy, University of Illinois at Chicago, Chicago, Illinois, USA.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Corcos
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods; D000368:Aged; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology; D003463:Cues; D004576:Electromyography; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009126:Muscle Relaxation; D009483:Neuropsychological Tests; D010300:Parkinson Disease / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology*; D013997:Time Factors