Acute and residual neuromuscular effects of displacement in indirect vibratory stimulation.

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, with intervals of 5 to 7 days (5 maximal voluntary contractions - MVC, 12 s of duration each and 5 min of recovery) between sessions. To determine the residual responses, the volunteers performed a MVC before and after each treatment for 12 s, with a 5-minute recovery. The experimental sessions were composed of isometric actions without vibrations (CONTROL) and two sessions of isometric actions with the addition of vibrations at 20 Hz and 3 mm (Sinusoidal Vibration A) and 5 mm (Sinusoidal Vibration B). Before and after each of the experimental sessions, an isometric evaluation without vibrations was performed. For the acute effect, it was verified that the addition of vibrations induced a facilitatory effect on the explosive strength variables (p < .05), independent of the type of studied displacement in relation to the control treatment. In short, it was verified that the addition of vibration induced an acute facilitating effect on the explosive strength. However, the induced effect was not persistent (residual effect) for the explosive strength.

Indirect sinusoidal vibrations induces an acute increase in explosive strength.

The purpose of this study was to examine the acute effect of indirect vibration on neuromuscular responses and fatigue resistance (electromyographic activity - EMG and force) during isometric exercise. Nineteen healthy men (age=22.4±2.7years; body mass=76.4±12.9kg, height=175±6.7cm) performed isometric elbow flexion exercises in three experimental treatments: only isometric exercise (control - CON); isometric exercise with the addition of sinusoidal vibrations (SVE1; frequency=20Hz, displacement=3.55±0.54mm); and isometric exercise with the addition of sinusoidal vibrations with frequency variation (SVE2; frequency=20±3Hz, displacement=3.6±0.8mm). The peak of the rate of EMG rise (RER) and the root mean square of biceps brachii during the first 200ms (RMS200bic) were significantly higher in SVE1 (RMS200bic, 25.57±11.70%MVC; RER, 266.91±130.16%MVCs-1) than CON (RMS200bic, 19.31±8.19%MVC; RER, 169.15±65.98%MVCs-1). Regarding force, in SVE1, compared to CON, significant increases were observed in peak of rate of force development (CON, 643.96±192.57N/s; SVE1, 845.54±292.84N/s), rate of force development in the first 200ms (CON, 382.92±138,63N/s; SVE1, 501.09±147.46N/s), and impulse in 200ms (CON, 8.56±3.56Ns; SVE1, 11.67±4.45Ns). The addition of indirect sinusoidal vibrations during exercise induced increases in the rate of force development (explosive strength), without affecting the peak force (maximal strength) and the ability to sustain strength production.