Linear and non-linear analysis of surface electromyograms in weightlifters

• Published in: European journal of applied physiology Vol. 84; no. 4; pp. 337 - 342
• Main Authors: Felici, F, Rosponi, A, Sbriccoli, P, Filligoi, G C, Fattorini, L, Marchetti, M
• Format: Journal Article
• Language: English
• Published: Germany Springer Nature B.V 01.04.2001
• Subjects: Adult; Determinism; Electrodes; Electromyography; Humans; Linear Models; Male; Models, Biological; Muscle, Skeletal - physiology; Nonlinear Dynamics; Weight Lifting - physiology; Weightlifting; Rome Italy; Italy
• ISSN: 1439-6319; 1439-6327
• DOI: 10.1007/s004210000364

The present research was aimed at investigating the peculiarities of surface electromyogram (sEMG) signals in 12 weightlifting athletes (WLA) and 9 control subjects (control group, CG) The sEMG signals were recorded from both vastus lateralis muscles during 20 s isometric contractions made at 30% and 60% of the maximal voluntary contraction (MVC). Ground reaction force (vertical component) was recorded using a force plate. The sEMG was analysed in the frequency domain and the median frequency (MDF) was computed over successive 1 s epochs. A non-linear technique, recurrence quantification analysis was also applied to assess the presence and time course of deterministic structures in sEMG. The percentage of determinism (%DET) was used as a synthetic parameter to quantify the amount of regularly repeating sEMG waves within the signal itself (bursts). In 5 WLA the sEMG displayed a clear burst activity centred at 11 Hz. These bursts were correlated with force output oscillations and were evident both at 30% and 60% MVC. The MDF decay with time was more evident in WLA than in CG subjects. The %DET increased in WLA, this increase being more evident during 60% MVC contractions. Our results seemed to suggest a special disposition among WLA for the development of long-term changes in firing probability during sub-maximal isometric exercise. The MDF and %DET data provided indications of a greater involvement of fast twitch muscle fibres in WLA than in CG.