Efeito agudo e residual da oscilação do parametro deslocamento na estimulação vibratória indireta sobre as respostas neuromusculares

Abstract

The aim of this study was to evaluate the effect of indirect vibratory stimulation on different magnitudes of displacement on acute and residual neuromuscular responses. Fifteen healthy volunteers were randomly submitted to 3 experimental sessions intervals of 5 to 7 days (5 MVC, 12 seconds of duration each and 5 minutes of recovery). For the determination of residual responses, the volunteers then performed a maximal isometric voluntary contraction (MVC) before and after treatment with the dominant limb for 12 seconds, with a 5-minute recovery. The experimental sessions were composed of isometric actions without vibrations (CONTROL - CO) and two sessions of isometric actions with addition of vibrations with 20 Hz and 3 mm (Sinusoidal Vibration A - SVA) and 5 mm (Sinusoidal Vibration B - SVB). Before and after each of the experimental sessions an isometric action without vibrations was performed to study the residual effect. To evaluate the electromyographic activity (EMG) was quantified for the agonist and antagonist muscles from the root mean square (RMS) of the EMG signal, the value between the onset at 200ms (BIC200 and TRIC200) by the integration method in the first 200 ms (BIC200EMG, TRIC200EMG), RMS peak (BICpeak and TRICpeak), between the peak of force and the end of the contraction (10s) (BICfatigue and TRICfatigue) and the peak of the rate of elevation of the biceps EMG signal (RER = EMG / Time). In the frequency domain, the peak of the median frequency of the onset EMG to the force peak (BICfrequency and TRICfrequency), and the median frequency of the EMG signal at the end of the contraction (BICFfrequency and TRICFfrequency) were quantified. For the force, the peak power (PF), the force production rate (RFD = Force / Time) in the 200 ms range (RFD200), the RFD peak (RFDpeak), the mechanical impulse in the first 200 ms I200) and the fatigue index (FI) by means of the percentage difference of pi force to the twelfth of the contraction. For the acute effect, it was verified that the addition of vibrations induced a facilitatory effect on the explosive strength (RER, RFDpeak, RFD200 and I200; p <.05) and on the maximum strength (PF; p <.05), independent of the type of displacement studied in relation to the control treatment. However, in the residual effect, a post - stimulation effect was observed in the direction of decreasing performance (fatigue) of the explosive strength (BIC200, RFDpeak and I200; p <.05), for the largest displacement studied (SVB). In sum, it was found that the addition of vibration induced an acute facilitation effect on the maximum strength and the explosive strength, but a greater displacement induced a decrease of the performance on the explosive strength.