title: Comparison of EMG during passive stretching and shortening phases of each muscle for the investigation of parkinsonian rigidity.
abstract: The aim of this study was to test the hypothesis in the literature that torque resistance of parkinsonian rigidity is the difference between the independent contributions of stretched and shortened muscles. The hypothesis was tested using muscle-specific stretch-shortening (MSSS) EMG ratio in this study. Nineteen patients with idiopathic Parkinson's disease (PD) and 18 healthy subjects (the mean age comparable to that of patients) participated in this study. The EMG activity was measured in the four muscles involved in wrist joint movement, i.e. flexor carpi radialis, flexor carpi ulnaris, extensor carpi radialis and extensor carpi ulnaris. The passive flexion-extension movement with a range of ±30∘ was applied at wrist joint. Root mean squared (RMS) mean was calculated from the envelope of the EMG for each of stretching and shortening phases. MSSS EMG ratio was defined as the ratio of RMS EMG of stretching phase and RMS EMG of shortening phase of a single muscle, and it was calculated for each muscle. MSSS EMG ratios were smaller than one in all muscles. These results indicate that all wrist muscles generate greater mean EMG during shortening than during stretching. Therefore, the torque resistance of parkinsonian rigidity cannot be explained as the simple summation of independent antagonistic torque pair.
authors.affiliation: School of Biomedical Engineering, Konkuk University, Choonju, 380-701, Korea.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Kwon
authors.affiliation: School of Biomedical Engineering, Konkuk University, Choonju, 380-701, Korea.
authors.forename: Ji-Won
authors.initials: JW
authors.lastname: Kim
authors.affiliation: School of Biomedical Engineering, Konkuk University, Choonju, 380-701, Korea.
authors.forename: Ji-Sun
authors.initials: JS
authors.lastname: Kim
authors.affiliation: Department of Neurology, Korea University College of Medicine, Seoul, Korea.
authors.forename: Seong-Beom
authors.initials: SB
authors.lastname: Koh
authors.affiliation: School of Biomedical Engineering, Konkuk University, Choonju, 380-701, Korea.|Research Institute of Biomedical Engineering, Konkuk University, Choonju, 380-701, Korea.
authors.forename: Gwang-Moon
authors.initials: GM
authors.lastname: Eom
authors.affiliation: Department of Biomedical Engineering, University of Iowa, IA, USA.
authors.forename: Tae-Hong
authors.initials: TH
authors.lastname: Lim
mesh_terms: D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D010300:Parkinson Disease / Q000503:physiopathology*; D016059:Range of Motion, Articular; D014955:Wrist Joint / Q000503:physiopathology*
keywords: EMG; parkinsonian rigidity; passive shortening; passive stretching