Reliability of pelvic floor muscle surface electromyography (sEMG) recordings during synchronous whole body vibration.

Daria Chmielewska,Grzegorz Sobota,Paweł Dolibog,Patrycja Dolibog,Agnieszka Opala-Berdzik,Emiliano Cè

doi:10.1371/journal.pone.0251265

Abstract

The primary aim of the study was to assess intraday and interday reliability of surface electromyography (sEMG) reflex activity of the pelvic floor muscles during synchronous whole-body vibration (S-WBV) of two intensities (30Hz/2mm; 40Hz/4mm) using band-stop filter and high-pass filter signal processing. The secondary aim of the study was to assess intraday and interday (test-retest) reliability of sEMG obtained from maximal voluntary contraction (MVC) test. We evaluated the intraday reliability of sEMG recordings obtained during sessions 1 and 2 performed on the same day. The sessions consisting of maximal voluntary pelvic floor muscle contraction and synchronous vibration sets with 1-hour rest in-between sessions 1 and 2 in healthy nulliparous women. The next intraday reliability was evaluated between the results of sessions 3 and 4 performed on the same day but followed at an interval of 4 weeks. to include the entire menstrual cycle. The interday reliability was determined based on the results of sessions 1 and 3 using the intraclass correlation coefficient (ICC 3,3). The intraday ICCs for band-stop filtered mean and median sEMG frequency and mean normalized sEMGRMS amplitude of the 30Hz/2mm (ICC = 0.89–0.99) and 40Hz/4mm vibration (ICC = 0.95–0.99) indicated substantial reproducibility. The intraday reliability of high-pass filter at 100-450Hz for these parameters was also substantial (30Hz/2mm ICC of 0.92 to 0.98; 40Hz/4mm ICC of 0.88 to 0.98). The interday reliability (session 1 vs. session 3) of the mean normalized sEMGRMS amplitude for band-stop filtered means of 40 Hz/4mm and 30Hz/2mm vibration recordings was substantial (ICC = 0.82 and 0.93). However, ICCs of the mean and median frequency were indicative of fair reliability (ICC of 0.43 to 0.59). The interday reliability of mean normalized sEMGRMS amplitude for high-pass filter at 100-450Hz was substantial (30Hz/2mm ICC of 0.90; 40Hz/4mm ICC of 0.73) for the 30Hz/2mm S-WBV and moderate (ICC = 0.73) for the 40/4mm S-WBV. The ICCs for mean and median sEMG frequency ICCs indicated slight to fair reproducibility (ICC of 0.16 to 0.56). The intraday reliability of the strongest MVC contraction and average MVC turned out substantial (ICC = 0.91–0.98). The interday reliability coefficients of the strongest MVC contraction and average MVCs were 0.91 and 0.82, respectively. Concluded, the intraday reliability proved satisfactory for all variables; however, the interday comparison showed sufficient ICC levels only for the mean amplitude. We therefore recommend this parameter should be used when analyzing PFM sEMG recorded during vibration. ICCs of the mean and median frequency for both signal processing methods were indicative of insufficient reliability and did not reach the threshold for usefulness. Our study showed similar reliability of PFM sEMG during S-WBV in case of the two filtering methods used.

Highlights

There is a growing interest of researchers and practitioners in the effect of whole body vibration (WBV) exercise in training [1]
The present study focuses on testing the intraday and interday reliability of Pelvic floor muscles (PFM) surface electromyography (sEMG) during synchronous whole body vibration (S-WBV) of two intensities using two signal processing methods described in literature
The intraclass correlation coefficient (ICC) for band-stop filtered mean and median frequencies and the mean normalized sEMGRMS amplitude of the 30Hz/2mm vibration indicated substantial reproducibility; the inter-measurement variability was low, i.e., between 3.15% and 15.62%

Summary

Introduction

There is a growing interest of researchers and practitioners in the effect of whole body vibration (WBV) exercise in training [1]. WBV has beneficial effects on neuromuscular performance as it improves the strength and power of muscles [2]. WBV has been used in clinical rehabilitation [3, 4] and preventive medicine. The most popular is sinusoidal vibration, which is applied through a vibrating surface. Some models apply the vibration in a side-alternating way (sequentially to the right and left foot), others transmit vibration via a plate that causes synchronic up and down movement of the right and the left foot–synchronous whole body vibration (S-WBV) [5]. Mechanical vibration of a human skeletal muscle induces a tonic vibration reflex [6] via activation of a polysynaptic pathway terminating on tonic alpha motor neurons [7] with the involvement of neural mechanisms associated with spinal reflexes, muscle tuning and central motor command [8]

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