Research Article Parkinsonian Rigidity Shows Variable Properties Depending on the Elbow Joint Angle

Copyright © 2013 Takuyuki Endo et al.This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Parkinsonian rigidity has been thought to be constant through a full range of joint angle. The aim of this study was to perform a detailed investigation of joint angle dependency of rigidity. We first measured muscle tone at the elbow joint in 20 healthy subjects and demonstrated that an angle of approximately 60 ∘ of flexion marks the division of two different angle-torque characteristics. Then, we measured muscle tone at the elbow joint in 24 Parkinson’s Disease (PD) patients and calculated elastic coefficients in flexion and extension in the ranges of 10∘–60 ∘ (distal) and 60∘–110 ∘ (proximal). Rigidity as represented by the elastic coefficient in the distal phase of elbow joint extension was best correlated with the UPDRS rigidity score