On the effect of muscular cocontraction on the 3-D human arm impedance

Harshil Patel, Gerald Oneill, Panagiotis Artemiadis

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


Humans have the inherent ability to perform highly dexterous tasks with their arms, involving maintenance of posture, movement, and interaction with the environment. The latter requires the human to control the dynamic characteristics of the upper limb musculoskeletal system. These characteristics are quantitatively represented by inertia, damping, and stiffness, which are measures of mechanical impedance. Many previous studies have shown that arm posture is a dominant factor in determining the end point impedance on a horizontal plane. This paper presents the characterization of the end point impedance of the human arm in 3-D space. Moreover, it models the regulation of the arm impedance with muscle cocontraction. The characterization is made by route of experimental trials where human subjects maintained arm posture while their arms were perturbed by a robot arm. Furthermore, the subjects were asked to control the level of their arm muscles' cocontraction, using visual feedback, in order to investigate the effect of muscle cocontraction on the arm impedance. The results of this study show an anisotropic increase of arm stiffness due to muscle cocontraction. These results could improve our understanding of the human arm biomechanics, as well as provide implications for human motor control - specifically the control of arm impedance through muscle cocontraction.

Original languageEnglish (US)
Article number2323938
Pages (from-to)2602-2608
Number of pages7
JournalIEEE Transactions on Biomedical Engineering
Issue number10
StatePublished - Oct 1 2014


  • Arm impedance
  • exoskeleton control
  • muscle cocontraction

ASJC Scopus subject areas

  • Biomedical Engineering


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