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This Article Full Text Full Text (PDF) All Versions of this Article: 101/1/387    most recent 00584.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Shin, D. Articles by Koike, Y. Search for Related Content PubMed PubMed Citation Articles by Shin, D. Articles by Koike, Y.

A Myokinetic Arm Model for Estimating Joint Torque and Stiffness From EMG Signals During Maintained Posture

¹Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama, Japan; ²Handong Global University, Pohang, Korea; and ³Core Reserch for Evolutional Science and Technology (CREST) Japan Science and Technology Agency, Kawaguchi, Japan

Submitted 13 October 2008; accepted in final form 4 November 2008

The perturbation method has been used to measure stiffness of the human arm with a manipulator. Results are averages of stiffness during short perturbation intervals (<0.4 s) and also vary with muscle activation. We therefore propose a novel method for estimating static arm stiffness from muscle activation without the use of perturbation. We developed a mathematical muscle model based on anatomical and physiological data to estimate joint torque solely from EMG. This model expresses muscle tension using a quadratic function of the muscle activation and parameters representing muscle properties. The parameters are acquired from the relation between EMG and measured torque. Using this model, we were able to reconstruct joint torque from EMG signals with or without co-contraction. Joint stiffness is directly obtained by differentiation of this model analytically. We confirmed that the proposed method can be used to estimate joint torque, joint stiffness, and stiffness ellipses simultaneously for various postures with the same parameters and produces results consistent with the conventional perturbation method.