Model based sensitivity analysis of EMG-force relation with respect to motor unit properties: Applications to muscle paresis in stroke

Ping Zhou*, Nina L. Suresh, William Z. Rymer

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

The sensitivity of the electromyogram (EMG)-force relation to changes in motoneuron and muscle properties was explored using a simulation approach, and by applying existing motoneuron pool, muscle force, and surface EMG models. The simulation results indicate that several factors contribute potently to known changes in the EMG-force relation in paretic stroke muscles. First, compression of the motor unit recruitment range with respect to the injected current tends to generate greater EMG amplitude at a given force, and to produce a highly nonlinear EMG-force relation. The overall mean slope of the EMG-force relation tends to be flatter, primarily because of this non-linear behavior. Second, with reductions of the mean motor unit firing rates, the slope of the EMG-force relation also tends to increase especially as the mean firing rates dropped substantially below the motor unit fusion frequency. Finally, similar effects were observed with a reduction in the number of motor units, and with variation in motor unit contractile properties, which also altered the EMG-force relation. These findings provide new insight toward our understanding of experimental EMG-force relations in both normal and pathological states, such as the abnormal EMG-force relations of paretis muscles in stroke.

Original languageEnglish (US)
Pages (from-to)1521-1531
Number of pages11
JournalAnnals of Biomedical Engineering
Volume35
Issue number9
DOIs
StatePublished - Sep 2007

Keywords

  • EMG-force relation
  • Motor unit property
  • Simulation
  • Stroke

ASJC Scopus subject areas

  • Biomedical Engineering

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