Muscle fiber conduction velocity and fractal dimension of EMG during fatiguing contraction of young and elderly active men

Gennaro Boccia, Davide Dardanello, Matteo Beretta-Piccoli, Corrado Cescon, Giuseppe Coratella, Nicoletta Rinaldo, Marco Barbero, Massimo Lanza, Federico Schena, Alberto Rainoldi

Research output: Contribution to journalArticlepeer-review


Over the past decade, linear and nonlinear surface electromyography (EMG) variables highlighting different components of fatigue have been developed. In this study, we tested fractal dimension (FD) and conduction velocity (CV) rate of changes as descriptors, respectively, of motor unit synchronization and peripheral manifestations of fatigue. Sixteen elderly (69 ± 4 years) and seventeen young (23 ± 2 years) physically active men (almost 3-5 h of physical activity per week) executed one knee extensor contraction at 70% of a maximal voluntary contraction for 30 s. Muscle fiber CV and FD were calculated from the multichannel surface EMG signal recorded from the vastus lateralis and medialis muscles. The main findings were that the two groups showed a similar rate of change of CV, whereas FD rate of change was higher in the young than in the elderly group. The trends were the same for both muscles. CV findings highlighted a non-different extent of peripheral manifestations of fatigue between groups. Nevertheless, FD rate of change was found to be steeper in the elderly than in the young, suggesting a greater increase in motor unit synchronization with ageing. These findings suggest that FD analysis could be used as a complementary variable providing further information on central mechanisms with respect to CV in fatiguing contractions.

Original languageEnglish
Article number162
Pages (from-to)162-174
Number of pages13
JournalPhysiological Measurement
Issue number1
Publication statusPublished - Dec 18 2015


  • electromyography
  • fractal dimension
  • muscle fiber conduction velocity
  • vastus lateralis
  • vastus medialis

ASJC Scopus subject areas

  • Biophysics
  • Physiology
  • Physiology (medical)


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