Study of muscle fatigue in isokinetic exercise with estimated conduction velocity and traditional electromyographic indicators
Schwartz, Fabiano Peruzzo; Bottaro, Martim; Celes, Rodrigo Souza; Pereira, Maria Claudia; Rocha Júnior, Valdinar de Araújo; Nascimento, Francisco Assis de Oliveira
http://dx.doi.org/10.1590/1517-3151.0528
Rev. Bras. Eng. Bioméd., vol.30, n4, p.312-321, 2014
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Abstract
Introduction: In the study of human biomechanics, it is often desirable to evaluate fatigue in the muscles that
are involved in performing a particular task. Identifying the phenomena responsible for this condition is a
problem that in most cases is complex and requires appropriate research mechanisms. Isokinetic dynamometry
(ID) and surface electromyography (SEMG) are two techniques widely used in studies on strength and
muscle fatigue. Their effectiveness is conditioned upon a good understanding of their limitations and the
adoption of procedures to fully exploit the potential of each one. The main goal of the present study is to
verify whether the electromyographic parameters, especially the conduction velocity (CV), are sensitive to
the fatigue instauration process within sets of maximal isokinetic contractions. CV is a basic physiological
parameter directly related to muscle activity and still little explored in experiments combining ID and SEMG.
Methods: Instrumentation architecture that combines ID and SEMG was used to estimate electromyographic
and biomechanical parameters in protocols of maximum intensity isokinetic knee extension exercises. This
architecture allows for limiting the parameter estimates to a specifi c region of isokinetic exercise, called the
isokinetic load range (ILR), where one can consider that the angular velocity is constant and the SEMG signals
are cyclo-stationary. Electromyographic signals were acquired using an array of electrodes. Conclusion: The
results suggest that CV and the other SEMG parameters, including amplitude and frequency descriptors, are
sensitive to detect a fatigue process only in protocols that restrict the analysis to ILR and that also bring the
subject to a state of fatigue quickly.
Keywords
Muscular fatigue, Dynamic contraction, Isokinetic dynamometry, Surface electromyography.