Continuous versus intermittent stochastic resonance whole body vibration and its effect on pelvic floor muscle...

To determine the optimal stochastic whole body vibration (SR-WBV) load modality regarding pelvic floor muscle (PFM) activity in order to complete the SR-WBV training methodology for future PFM training with SR-WBV.

The continuous and the intermittent SR-WBV modalities were tested by means of electromyography in two independent groups (27 women 8 weeks to 1-year postpartum and 23 women nulliparae or >1-year postpartum) with self-reported stress urinary incontinence. The change in the PFM activity within a single set and over three sets were calculated for both SR-WBV modalities together (time effect) and for both SR-WBV modalities separately (modality-time interaction).

There was no statistically significant or clinically relevant change in PFM activity over time or PFM fatigue in either SR-WBV modality within one or three sets and no difference between the modalities or the groups.

The lack of change in PFM activity could be due to a no more than moderate to submaximal PFM activity during SR-WBV, the maintenance of reflexive PFM activity despite PFM fatigue or a compensation of slow red PFM fiber fatigue by an increase of innervation frequency and motor unit recruitment of the fast white fibers. As there is no SR-WBV modality dependent difference regarding PFM activity, the continuous modality is recommended in clinical practice as it is easier to apply and less time consuming.