title: Test-retest reliability of muscle fiber conduction velocity and fractal dimension of surface EMG during isometric contractions.
abstract: The aim of this study was to determine the test-retest reliability of muscle fiber conduction velocity (CV) and fractal dimension (FD) obtained from multichannel surface electromyographic (sEMG) recordings.
  
  
  
  Forty healthy recreationally active subjects (20 men and 20 women) performed two elbow flexions on two trials with a 1 week interval. The first was a 20% maximal voluntary contraction (MVC) of 120 s, and the second at 60% MVC held until exhaustion. sEMG signals were detected from the biceps brachii, using bi-dimensional arrays.
  
  
  
  Initial values and slope of CV and FD were used for the reliability analysis. The intraclass correlation coefficient (ICC) values for the isometric contraction at 20% MVC were (-0.09) and 0.67 for CV and FD respectively; whereas the ICC values at 60% MVC were 0.78 and 0.82 for CV and FD respectively. The Bland Altman plots for the two isometric contractions showed a mean difference close to zero, with no evident outliers between the repeated measurements: at 20% MVC 0.001 53 for FD and  -0.0277 for CV, and at 60% MVC 0.006 66 for FD and 0.009 07 for CV.
  
  
  
  Overall, our findings suggest that during isometric fatiguing contractions, CV and FD slopes are reliable variables, with potential application in clinical populations.
authors.affiliation: Rehabilitation Research Laboratory 2rLab, Department of Business Economics, Health and Social Care, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland.
authors.forename: Matteo
authors.initials: M
authors.lastname: Beretta-Piccoli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: D'Antona
authors.forename: Cristian
authors.initials: C
authors.lastname: Zampella
authors.forename: Marco
authors.initials: M
authors.lastname: Barbero
authors.forename: Ron
authors.initials: R
authors.lastname: Clijsen
authors.forename: Corrado
authors.initials: C
authors.lastname: Cescon
mesh_terms: D000328:Adult; D004576:Electromyography; D005260:Female; D017709:Fractals; D006801:Humans; D007537:Isometric Contraction; D007700:Kinetics; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000502:physiology*; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult