Partition between volitional and induced forces in electrically augmented dynamic isometric muscle contractions

Eran Langzam, Yael Nemirovsky, Eli Isakov, Joseph Mizrahi

Research output: Contribution to journalArticlepeer-review


Augmentation of force in partially deficient muscles can be achieved by combining electrical stimulation (ES) with their volitional activation (hybrid activation). However, while the overall torque results from the combination of the volitional and the electrically-induced torque components, the exact share between these components is not known. In a previous work, we described a method to resolve the share between the torque components under isometric static contractions. In this work, we extend our analysis to the case of isometric dynamic contractions. Five healthy subjects were instructed to contract their Tibialis Anterior (TA) muscles according to a typical gait-like dynamic torque pattern, that was visually displayed to them, while monitoring their actual ankle torque and TA electromyography (EMG). These experiments were done with and without augmented activation by means of ES. A computational algorithm was developed to dissociate the volitional from the overall torque, based on EMG signal processing and on precalibration of the dynamic system of the volitional torque versus EMG. The results indicated the quantitative relations between decrease in the volitional torque and the required increase in ES enhancement. The developed method also demonstrated what ES intensity profile is necessary to produce a desired overall torque output. This provides the means for designing an adaptive rehabilitation device for the hybrid activation of deficient muscles.

Original languageEnglish
Pages (from-to)322-335
Number of pages14
JournalIEEE Transactions on Neural Systems and Rehabilitation Engineering
Issue number3
StatePublished - Sep 2006
Externally publishedYes


  • Adaptive rehabilitation system
  • Dynamic contractions
  • Electrical stimulation
  • Hybrid excitation
  • Muscle force augmentation
  • Tibialis anterior


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