Análise do sinal miolétrico a partir de um parâmetro temporal / Analysis of myoelestric signal based on temporal information

RESUMO

This study describes the analysis of muscular contraction based on temporal Information of the myoelectric signal. This temporal information is the histogram of the adjacent zero crossings time intervals (ZCI) of the signal. Since the myoelectric signal can be seen as a random signal, the ZCI histogram was characterized by its statistical properties. In this paper, the systematic way of obtaining such statistical properties was to adjust a probability distribution function, the Weibull function, to the ZCI histogram. The volunteers (16 men, 22 ± 2.98years; and 11 women, 20.6 ± 1.77years) were healthy, right-handed and students of physical education at the Federal University of Rio de Janeiro. The group was divided by sex and practice of specific physical activities, being then classified in Trained (T) and Not-Trained (NT). The volunteers had to go through 3 basic stages: two collection phases of the myoelectric signal and a period of training between the two collections. The studied muscle was the right biceps braquialis contracting ai 5 different load conditions (without Load (SC), 30 por cento, 66 por cento, 85 por cento and 100 por cento) calculated according to a maximum voluntary contraction test (MVC). The acquisition test was accomplished by means oU isometric contractions with duration of 6 seconds each, with elbow at 90° of flexion and rest time of 2 minutes. The training stage consisted of 9 sessions developed on different days, and it reproduced the conditions of signal acquisition, just differing in the used load (66 por cento of MVC) and in the rest time (45 seconds). In each one of the load conditions a histogram of relative frequency was generated and the Weibull function was adjusted. The results of central tendency and dispersion of the adjusted function pointed out that they can contribute to the analusis of muscular contraction