Neuromuscular electrical stimulation (NMES) of the pelvic floor (PFM) is a popular adjunctive therapy to pelvic floor exercises (PFE) in those with stress urinary incontinence (SUI). The purpose of this study was: firstly, that a new NMES device elicits PFM contractions and a sham does not and secondly, that the sham is considered a credible therapy by users for use in an upcoming RCT.

 

While PFE are effective in increasing PFM strength, their location make it difficult to confirm an appropriate contraction occurs. Less than half of those given instructions can contract their PFM, consequently adjunctive therapies such as NMES are frequently used. Evidence regarding NMES for SUI is equivocal and subjective perception of an NMES elicited contraction cannot be relied upon as studies show a contraction occurs in only 11–16 %. Twenty healthy females with a mean age of 34.8 years (SD 16.3) and mean BMI of 25.4 kg/m2 (SD 5.7) were recruited for this study.

This was a controlled, single-center, cross-over study and all subjects gave informed consent to receive Treatment A and B. Each consisted of a garment with an array of eight electrodes and a muscle stimulator. Treatment A and B’s stimulating surface area were 1,202 cm2 and 1,260 cm2 respectively and parameters were modified to produce a sensory response (Treatment A) and motor response (Treatment B). Ultrasound (US) data were acquired transabdominally once subjects reached a maximum threshold intensity in standing. An appropriate PFM contraction was defined as one resulting in cranial displacement of the bladder observed on US, which was measured with on-screen calipers. Subjects were blinded to US and the data were also verified by a blinded independent assessor. Additionally, subjects completed questionnaires to verify treatments were perceived as valid options in terms of sensation and determine which treatment option was deemed more effective.

Contractions were observed for all participants during Treatment B and none were apparent for Treatment A (Fig. 1). Consequently, the paired t-tests are effectively one-sample t-tests of whether the mean contraction for Treatment B is equal to zero. Mean displacement for Treatment B was 0.96 cm (SD 0.53) and 1.04 cm (SD 0.58) with respect to unblinded and blinded assessment. Direct comparison of both assessments for Treatment B indicates that unblinded measurements were systematically smaller than the blinded measurements, with a mean (95 % CI) difference of −0.08 cm, p=0.007. Though statistically significant, the difference is small, representing 8 % of the mean value. 13 subjects thought Treatment A was ‘an effective treatment’ and 7 were ‘not sure’. 15 believed Treatment B was ‘an effective treatment’ and 5 were ‘not sure’. There was no clear preference for either treatment. 10 preferred Treatment A (50 %), 7 preferred Treatment B (35 %) and 3 had no preference (15 %). When subjects were asked to compare effectiveness of treatments, 10 thought Treatment A was ‘less effective’ than Treatment B, 1 thought they were ‘equally effec-ive’ and 9 ‘didn’t know’.

The primary objective was to verify that Treatment A did not elicit a PFM contraction and Treatment B did. Treatment B consistently elicited a PFM contraction and the sham (Treatment A) did not. Unblinded and blinded assessment gave identical results for each treatment although the unblinded were slightly smaller in measurement (0.08 cm). This may reflect differences between the individuals who made the measurements, not necessarily between assessments per se. One of the key contributors to effective PFM training is confirmation of a correct volitional contraction. The same should apply when using NMES. If NMES does not elicit a contraction, then there is no benefit in using it to increase strength or endurance of the PFM. This study showed that Treatment B elicited a contraction in 100 % of the subjects whereas the Treatment A failed to elicit contractions despite being perceived as a potential treatment intervention.