Correlation between motor unit synchronization estimated through intramuscular and surface EMG in the vastus medialis obliquus: a validation study

Cescon, Corrado and Vistarini, Ausilia and Pisegna, Caterina and Vannini, Beatrice and Zampella, Cristian and Calanni, Luca and Soldini, Emiliano and D'Antona, Giuseppe (2022) Correlation between motor unit synchronization estimated through intramuscular and surface EMG in the vastus medialis obliquus: a validation study. In: ISEK 2018 Congress - XXII Congress of the International Society of Electrophysiology and Kinesiology, June 22 -25, 2022, Quebec City, Canada.

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Abstract

BACKGROUND AND AIMS: During fatiguing contractions synchronization between the firing times of simultaneously active motor units (MUs) is generally assumed to increase. Recent studies have added weight to this hypothesis using indirect estimates of synchronization derived from surface electromyographic (EMG) interference signals, such as fractal dimension (FD), sub-band skewness or multi-fractal detrended fluctuation analysis. However, previous studies using intramuscular EMG (iEMG) have reported no change in MU synchronization during fatigue. Therefore, the aim of this study was to investigate the correlation between MU synchronization detected through intramuscular EMG and the FD of the sEMG signal in the vastus medialis muscle during isometric fatiguing contractions METHODS: 16 healthy men (30±9 years) volunteered to participate in the study. Participants performed two maximal voluntary contractions (MVC) followed by a 5% MVC of 5 min, and immediately afterwards a third MVC. EMG signals were detected (a) using a couple of fine-wire electrodes and (b) two couples of bipolar surface electrodes from the left vastus medialis obliquus. The iEMG signal was fully decomposed using EMGLAB through the Montreal algorithm. Synchronization of MU firings was then calculated using the Synch Index as proposed by De Luca et al. (1993) on cross-correlation histograms. Initial value of FD of the EMG signal was calculated. Correlation between the Synch Index and FD was investigated using Spearman correlation coefficient. RESULTS: A statistically significant moderate correlation was found between the Synch Index and FD (rho= -0.3; p<0.05) (Figure 1). CONCLUSIONS: The results suggest that during fatiguing isometric contractions, changes in the FD of the sEMG signal may be related to an increase in MU synchronization. Therefore, FD appears to be a valid alternative to the use of intramuscular EMG for the study of MU synchronization. Figure 1: Correlation analysis between the Synch Index (intramuscular EMG) and the fractal dimension (FD) of the sEMG signal. The two indices were calculated during the initial and final 50 s of the 5% MVC isometric contraction of the vastus medialis obliquus muscle (rho = -0.3, p=0.18).

Item Type:	Article in conference proceedings or Presentation at a conference (Poster)
Subjects:	Engineering > General engineering > Bioengineering, biomedical engineering & clinical engineering
Department/unit:	Dipartimento economia aziendale, sanità e sociale > Laboratorio di ricerca in riabilitazione
Depositing User:	Corrado Cescon
Date Deposited:	06 Feb 2024 06:38
Last Modified:	06 Feb 2024 06:40
URI:	http://repository.supsi.ch/id/eprint/14968

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