Características do sinal mecanomiográfico em atletas velocistas, fundistas e indivíduos sedentários / Characteristic of the mechanomyography signals in long-distance runners, sprinters and sedentary subjects

ABSTRACT

The purpose of this study was to evaluate whether mechanom graphy (MMG) allowed for the detection of differences in the mechanical and physiological behavior of the vastus lateralis muscle of long-distance runners, sprinters and sedentary subjects. Assuming that the above muscle had different muscle fiber composition in long-distance runners compared to sprinters, a difference was expected in the MMG signal produced during muscle contraction in these two groups. Thirty male subjects (1O long-distance runners, 1O sprinters and 1O sedentary subjects) without any history of neuromuscular injury or disease participated in the study. ln the first set of tests, the subjects performed different levels of voluntary effort, whereas in a second set of tests contractions were elicited with increasing frequencies of electrical stimulation of the femoral nerve. Root mean square (RMS) values and the median frequency (MDF) were obtained from the MMG signals in the three groups. The obtained MMG signals did not show a statistical difference among the three groups, neither in magnitude nor in frequency content, both in the voluntary and electrically elicited contractions. However, the mean RMS values of the MMG signals were always smaller for the long-distance runners compared to the other two groups, both in the voluntary and in the electrically elicited contractions, whereas the MDF mean values for the sprinters were always higher when compared to the other two groups in the voluntary test. Although the results point towards some tendencies in the behavior of the MMG signals in different athletes, MMG is not a technique that allows for an easy detection of the mechanical and physiological behavior of muscles with different fiber type composition (differently from what has been proposed in the literature.