Comparison of EMG during passive stretching and shortening phases of each muscle for the investigation of parkinsonian rigidity

Yuri Kwon, Ji Won Kim, Ji Sun Kim, Seong Beom Koh, Gwang Moon Eom, Tae Hong Lim

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3 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)S2155-S2163
JournalBio-Medical Materials and Engineering
Publication statusPublished - 2015 Jan 1



  • EMG
  • parkinsonian rigidity
  • passive shortening
  • passive stretching

ASJC Scopus subject areas

  • Biomaterials
  • Biomedical Engineering

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