Atividade elétrica dos músculos da coxa e transmissibilidade em baixas frequências de vibração de corpo inteiro

Abstract

The literature suggests that training involving high vibration frequencies promotes beneficial effects on the neuromuscular system. It has recently been found that low frequencies can provide similar benefits. However, few studies have investigated muscle activation at frequencies below 30Hz. The aim of this study was to verify if the increase in the frequency of whole body vibration (WBV) promotes an increase in the electrical activity of the thigh muscles and a reduction in the transmissibility to the head. Correlations between transmissibility and body composition variables were also tested. Fifteen healthy and physically active men participated in this study. Volunteers attended the laboratory on four visits. Where the characterization measures were obtained and the electrode points marked, followed by a warm-up and maximum voluntary isometric contraction tests. On the following three visits, volunteers performed experimental IVC sessions consisting of four sets of 30s with intervals of 30s between sets in a semi-squat position with knees at a 140° angle, feet hip-width apart, elbows extended forward and looking at a fixed point. The frequencies used were (5, 15, 22Hz). During IVC, the electromyographic activity of the rectus femoris and biceps femoris was recorded, as well as the acceleration in the head. The (RMS) of the rectus femoris was higher at the frequency of 22Hz compared to 5Hz (p = 0.) and 15Hz (p=0.025). Transmissibility at the 5Hz frequency was higher when compared to 22Hz and 15Hz (p=0.025). There was a correlation between the RMS of the rectus femoris between the frequencies of 5 and 15Hz (r=0.876); 5 and 22Hz (r=0.714); 15 and 22Hz (r=0.878) and negative correlations were found between transmissibility at the 22Hz frequency and skinfolds. The results suggest that at higher frequencies compared to others used in this study, they promote greater muscle activation while increasing the capacity to reduce head acceleration (transmissibility reduction). Furthermore, transmissibility depends on variables of body composition and muscle activation of the rectus femoris.