Relationship between ankle stiffness structure and muscle activation.

Hyunglae Lee, Shuo Wang, Neville Hogan

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


This paper presents a characterization of the structure of ankle stiffness under multiple levels of muscle activation and the relationship between them. A multi-variable impedance estimation method using a wearable ankle robot enabled clear identification of ankle stiffness structure in the space consisting of the sagittal and frontal planes. With visual feedback showing current and target muscle activation levels, all subjects could successfully maintain multiple target levels (5%∼30% of the maximum voluntary contraction level). Stiffness increased with muscle activation, but the increase was more pronounced in the dorsiflexion-plantarflexion direction than in the inversion-eversion direction, which resulted in a characteristic "peanut" shape. The relation between measured muscle activation level and ankle stiffness was evaluated. All subjects showed a highly linear relation not only for the two principal axis directions of the ankle, i.e., dorsiflexion-plantarflexion and inversion-eversion, but also for the average stiffness value of all directions. These major findings were consistent both for the tibialis anterior and triceps surae activation.

Original languageEnglish (US)
Pages (from-to)4879-4882
Number of pages4
JournalConference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference
StatePublished - 2012
Externally publishedYes

ASJC Scopus subject areas

  • Computer Vision and Pattern Recognition
  • Signal Processing
  • Biomedical Engineering
  • Health Informatics


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