title: Muscle fiber conduction velocity and fractal dimension of EMG during fatiguing contraction of young and elderly active men.
abstract: 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.
authors.affiliation: Motor Science Research Center, School of Exercise & Sport Sciences, SUISM, Department of Medical Sciences, University of Turin, 12, Piazza Bernini, 10143 Torino, Italy. CeRiSM Research Center 'Sport, Mountain, and Health', via del Ben 5/b, 38068, Rovereto (TN), Italy.
authors.forename: Gennaro
authors.initials: G
authors.lastname: Boccia
authors.forename: Davide
authors.initials: D
authors.lastname: Dardanello
authors.forename: Matteo
authors.initials: M
authors.lastname: Beretta-Piccoli
authors.forename: Corrado
authors.initials: C
authors.lastname: Cescon
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Coratella
authors.forename: Nicoletta
authors.initials: N
authors.lastname: Rinaldo
authors.forename: Marco
authors.initials: M
authors.lastname: Barbero
authors.forename: Massimo
authors.initials: M
authors.lastname: Lanza
authors.forename: Federico
authors.initials: F
authors.lastname: Schena
authors.forename: Alberto
authors.initials: A
authors.lastname: Rainoldi
mesh_terms: D000368:Aged; D004576:Electromyography; D017709:Fractals; D006801:Humans; D008297:Male; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D055815:Young Adult