Electromyographical analysis of submaximal isometric contraction in older and young adults

INTRODUCTION: The aging process is accompanied by physical, social as psychical changes. Skeletal-muscle adaptations are related to the decrease in muscular strength. OBJECTIVE: The aim of this study was to verify the aging effects in biceps brachiali isometric contractions fatigue comparing young and older subjects. METHODS: This study sample was composed 16 young adults (22.75 ± 3.47 years old) and 15 older adults (68.6 ± 3.11 years old). The protocol count on a submaximal voluntary contraction (SVC) and a hand weight of 5% of each subject's body mass. The contraction was carried on with a 90º flexion of the elbow, shoulder in neutral position and supinated radius-ulnar, during 35 seconds. The EMG signals were caught through a couple of electrodes on the lateral portion of the biceps brachiali. The signal was cut in two windows of 3 seconds each in the beginning and in the end, without consideing the first and last 2.5 seconds. From each window we obtained the median frequency values (MF) and the values were normalized with the first window of each individual. We plotted a line between the windows and found the inclination coefficient. To reach the specific differences there was applied a non-parametric U Mann-Whitney test. RESULTS: Both the lines indicated decline: -0.1494 for young subjects and -0.0521 for older subjects, however, there were no significant differences between them (p = 0.129). CONCLUSION: It seems that the submaximal conditions in this study were not enough to produce differences in the EMG sign between young and older subjects.