Bioelectrical activity of the pelvic floor muscles during synchronous whole-body vibration - a randomized controlled study

The aim of this study was to evaluate bioelectrical activity of the pelvic floor muscles during synchronous low- and high-intensity whole-body vibration in three trials of varying duration (30s, 60s and 90s). Another aim was to assess pelvic floor muscle fatigue during 90s whole-body vibration. The study participants were young continent women. Intervention: Group I and II subjects participated in synchronous whole-body vibrations which were carried out on a vibration platform (Fitvibe 600, Gymna Uniphy N.V.) producing vertical oscillations. The frequency and peak-to-peak displacement of vibration were set individually for each group, i.e. 2 mm/20 Hz for group I and 4 mm/40 Hz for group II. Test participants were in a static squat position during the exercises. Each subject was asked to stand on the platform, loading their feet uniformly, with the knee and hip joints bent at 35 degrees and the upper extremities stretched horizontally forwards, holding on to a railing. Control participants (group III) performed static squat exercises similar to those used in the study groups I and II but without the concurrent application of vibrations. Three static squat exercise trials of varying duration (30s, 60s and 90s) were performed in a randomized order. A 10-min rest period was used between trials in order to eliminate any potential fatigue. Measurements: Pelvic floor surface electromyography (sEMG) activity was recorded using a vaginal probe during three experimental trials limited to 30s, 60s and 90s in accordance with SENIAM recommendations (Surface ElectroMyoGraphy for the Non- Invasive Assessment of Muscles). The experiment consisted of two phases: 1/ the maximal voluntary contractions (MVC) procedure to recruit pelvic floor muscles and 2/ three static exercise trials of varying duration (30s, 60s, 90s) performed in a randomized order to determine PFM activity during (groups I, II) or without (group III) WBV. During the first phase, each participant was instructed to perform MVC of the pelvic floor muscles as forcefully as possible for about 5 seconds. Three attempts were made with 60-second rests between each contraction to reduce the effect of muscle fatigue. The MVC procedure to recruit pelvic floor muscles was carried out in supine lying, the hip and knee were positioned at 30° and 90° of flexion, respectively. The positions were controlled with the goniometer. The mean amplitude and variability of the signal were normalized to the Maximal Voluntary Contraction. The mean amplitude as well as the mean and median frequency of the sEMG signal were additionally measured to determine the effect of fatigue during the 90-second sEMG recordings. sEMG probe was placed by gynecologist; testing procedure was supervised by physiotherapist.