Introduction
Pelvic floor muscle training (PFMT) has level 1A scientific evidence for the treatment of urinary incontinence and pelvic organ prolapse (POP) [
1‐
3]. Unfortunately, women who have very weak PFM have often been excluded from these studies. Approximately 30% of women are unable to contract their pelvic floor muscles (PFM), even after thorough individual instruction [
4,
5]. Following instrumental vaginal deliveries, PFM strength has been found to be reduced by 54–66%, and endurance by 53% and 65%, respectively [
6]. Both electrical stimulation (ES) and vaginal facilitation techniques can be used to facilitate PFM contraction [
9]. Intravaginal electrical stimulation (iES) of weak PFM may be a better treatment approach than PFMT. There is currently little evidence to support this hypothesis. When commencing our pilot study, there had only been one randomised controlled trial (RCT) that had investigated the effect of iES on PFM strength in women with weak PFM [
8]. Mateus-Vasconcelos et al. (2018) investigated 132 women with a PFM strength of 0 or 1 measured by vaginal palpation using the Modified Oxford Scale, where 33 women were randomised to iES [
8]. They found that iES was no better than PFMT, but they likely did not use optimal electrotherapy parameters and only measured PFM strength with vaginal palpation. To our knowledge, any other studies that had investigated iES prior to 2020 included subjects that were not very weak [
10,
11], had small study samples [
9], no control group [
9] or did not have subjects simultaneously voluntarily contract their PFM with the electrical current [
8,
10,
11]. There is an urgent need for treatment options for women with weak PFM. The hypothesis of the present study was that iES is more effective than PFMT in improving PFM strength in women with very weak PFM.
Results
Subject recruitment and data collection were undertaken between April 2021 and November 2022. A total of 15 women were assessed as eligible for participation in the study. Eight were randomised to iES and 7 to PFMT. There were two dropouts in the iES group. One withdrew due to a sudden death in the family and the other was lost to follow up just prior to post-testing. Statistical analyses were undertaken on the 13 women who completed post-testing (Fig.
1). Demographical data are presented in Table
1. Median age of the participants was 49 years (range 36–77) and parity 2.1 (range 1–3). At baseline mean PFM strength was 6.9 (SD 1.1) and 6.0 (SD 2.4) cmH
2O in the iES and PFMT group respectively. There were no significant differences between groups at baseline (
p = 0.392) (Table
1).
Table 1
Descriptive statistics and baseline values for women randomised to electrical stimulation (iES, n = 6) and pelvic floor muscle training (PFMT, n = 7). Results are given as frequencies and percentage for categorical data and means with standard deviation for continuous data
Higher education (> 4 years university) | 3 (50.0%) | 2 (28.6%) | 0.429 |
Postmenopausal | 4 (66.7%) | 1 (14.3%) | 0.053 |
Caesarean section | 0 | 2 (28.6%) | 0.161 |
Vacuum | 1 (16.7%) | 1 (14.3%) | 0.906 |
Forceps | 2 (33.3%) | 0 | 0.097 |
Urinary incontinence | 6 (100%) | 7 (100%) | |
Stress urinary incontinence | 6 (100%) | 6 (85.7%) | 0.335 |
Urgency urinary incontinence | 4 (66.7%) | 6 (85.7%) | 0.416 |
ICIQ-UI SF | 10.2 (1.6) | 9.7 (3.1) | 0.754 |
Pelvic organ prolapse symptoms |
Vaginal bulging | 1 (16.7%) | 2 (28.6%) | 0.612 |
Vaginal symptom score (ICIQ-VS) | 15.7 (12.5) | 11.1 (13.0) | 0.538 |
Bowel dysfunction |
Bowel urgency * | 4 (66.7%) | 3 (42.9%) | 0.391 |
Flatus incontinence * | 2 (33.3%) | 1 (14.3%) | 0.416 |
Faecal incontinence * | 3 (50.0%) | 1 (14.3%) | 0.164 |
Sexual dysfunction ICIQ-FlutSex | 9.8 (13.5) | 3.3 (4.1) | 0.245 |
PFM function—manometry |
Maximal voluntary contraction (cmH2O) | 6.9 (1.1) | 6.0 (2.4) | 0.392 |
PFM endurance (cmH2Osec) | 26.3 (14.9) | 41.9 (20.5) | 0.152 |
Vaginal resting pressure (cmH2O) | 27.1 (6.7) | 32.9 (18.4) | 0.480 |
PFM function—EMG |
Maximal voluntary contraction (µV) | 14.0 (3.9) | 14.4 (10.1) | 0.921 |
Vaginal resting activity (µV) | 7.4 (3.9) | 5.9 (5.9) | 0.693 |
Change in PFM strength and endurance, and power calculations
Both groups showed increases in PFM strength from baseline that exceeded the minimal detectable changes found in the study by Tennfjord et al. [
20] (iES 12.3, SD 12.0 vs PFMT 10.0, SD 8.1 cmH
2O. No significant difference, however, was found between groups (2.3, 95%CI −10.0–14.7 cmH
2O,
p = 0.886). With a power of 0.80 (1 – β) and Type 1 error rate of 5% (α), we need a sample size of 95 women in each group to detect a difference between the two groups (Table
2). PFM endurance also improved in both groups (iES 95.7, SD 81.7 vs PFMT 73, SD 69.5 cmH
2O). There was no significant difference between groups (22.7, 95%CI −69.5–114.9,
p = 0.886) (Table
2).
Table 2
Changes in pelvic floor muscle (PFM) strength (maximal voluntary contraction, MVC), endurance and vaginal resting pressure, measured with Camtech manometer. Mean with 95% confidence interval
MVC (cmH2O) | 12.3 (−0.3–24.9) | 10.0 (2.5–17.4) | 2.3 (−10.0–14.7) | 0.886 | 95 |
Endurance (cmH2Osec) | 95,7 (9.9–181,4) | 73.0 (8.7–137.3) | 22.7 (−69.5–114.9) | 0.886 | 74 |
Vaginal resting pressure (cmH2O) | −0.7 (−6.6–5.0) | −2.2 (−17.3–12.9) | 1.5 (−13.9–16.8) | 0.317 | 925 |
Change in symptoms
Change in symptoms are presented in Table
3. Improvements in ICIQ-UI SF scores was found in both groups, with improvements tending to be a little better in the PFMT, but not reaching significance (3.7, 95% CI −0.4–7.9,
p = 0.073). Participants in both groups reported fewer episodes of urinary incontinence (iES 67% and 57% PFMT). All subjects with POP symptoms reported improvement in quality of life in relation to vaginal symptoms with the difference between groups tending significance in favour of the PFMT group (2.5, 95% CI −0.3–5.3,
p = 0.061). Sample size calculations for changes in urinary, vaginal bowel and sexual symptoms, based on ICIQ questionnaires, are presented in Table
3Table 3
General improvements and specific improvements in bladder-, pelvic organ prolapse- (POP) and bowel- symptoms in the electrical stimulation (iES, n = 6) and pelvic floor muscle training (PFMT, n = 7) group
General improvements |
Improved | 6/6 (100%) | 7/7 (100%) | | NA | |
Satisfied | 6/6 (100%) | 7/7 (100%) | | NA | |
Recommend others the same treatment | 6/6 (100%) | 7/7 (100%) | | NA | |
Improvement in bladder symptoms |
Change in ICIQ-UI SF score | −0.4 (SD−3.5) | −4.1 (SD− 3.2) | 3.7 (−0.4–7.9) | 0.073 ¤ | 12 |
Reduced frequency of UI (0–5) | 4/6 (67%) | 4/7 (57%) | | 0.529 * | |
POP symptoms |
Change in ‘vaginal bulging’, for women initially having the symptom | 0/1 | 1/2 (50%) | | 0.386 * | |
Change in QoL vaginal score (0–10) | −1.5 (Range −5–1) | −4.0 (Range −7–−1) | 2.5 (−0.3–5.3) | 0.061 ¤ | 14 |
Bowel symptoms |
Change in bowel urgency (0–5) | 0.2 (Range −1–1) | −0.6 (Range −2–2) | 0.7 (−0.6–2.0) | 0.117 ¤ | |
Change in QoL bowel score (0–10) | −1.5 (Range −5–0) | −2 (Range −6–0) | 0.5 (−2.1–3.1) | 0.767 ¤ | 335 |
Improvement in sexual function | | | | |
Change in ICIQ-Flut Sex score | −6.3 (SD−7.8) (n = 3) | −2.7 (SD 4.1) (n = 6) | 3.7 (−12.7–5.4) | 0.500 ¤ | 38 |
User perspective and adverse events
All subjects in both groups (100%) reported improvements in their symptoms of PFD, that they were satisfied with the treatment, and that they would recommend the same therapy to others (Table
3). One subject reported pain of her vaginal lining after using iES for a period. She was advised to stop using the device for two weeks and then recommence using more lubricant. No pain or discomfort was reported thereafter. Two women had some technical difficulties with their NeuroTrac MyoPro Plus machine which they reported to their treating PT immediately.
Responder analyses
There were three responders in each group. Responders (n = 6) increased their strength by 19.6 ± 6.9 cmH2O whereas non-responders (n = 7) increased by 3.5 ± 2.7 cmH2O (p = 0.001). Similarly, responders improved their PFM endurance more than non-responders (151.8 ± 41.2 vs 24.9 ± 23.9 cmH2O). At baseline non-responders were significantly weaker than responders (5.2 ± 1.7 vs 7.8 ± 1.0 cmH2O, p = 0.014) and had lower PFM endurance (24.3 ± 23.9 vs 19.8 ± 6.9 cmH2O/s, p = 0.035) compared to responders. We found no significant differences between or within the groups regarding age, adherence, or birth history. There was a trend towards significance of the non-responders having had larger babies than the responders (4149 g vs 3649 g, p = 0.222). A sample size of 16 participants in each group would have been required to a detect significant difference.
Adherence
Adherence was very good for subjects in both groups, with no significant difference being found between groups. The number of days performing iES/PFMT was 154 of 187 (SD 31.8, 82%) and number of physiotherapy visits was 11.2 out of 12 (range 10–12, 93%).
Discussion
Our study shows that both iES and PFMT can improve PFM strength, endurance and symptoms of PFD in women with weak PFM. Due to the small number of participants, however, we were unable to determine if iES was a more effective therapy than PFMT. Based on our results, a large-scale RCT with 95 patients in each group is required to answer this question.
Past studies investigating the effect of PFMT have often excluded women with weak or no voluntary contraction of PFM [
1]. Women with weak PFM and damage to their pelvic floor support have a higher prevalence of UI and POP compared to women with good support. Such women may be at increased risk of developing PFD that not only significantly impacts on their quality of life but also on health care costs.
Pelvic floor muscle contraction involves complex neurophysiological processes. Vaginal palpation is a proprioceptive stimulus that can be used to facilitate correct voluntary contraction of the PFM [
7]. Electrical stimulation applied intravaginally can also facilitate PFM contraction by means of stimulating the pudendal nerve and its branches and producing a reflex contraction. Both perineal rehabilitation methods may be beneficial in women who have difficulty contracting their PFM.
At the time of planning our study there was only one RCT by Mateus-Vasconcelos et al. (2018) that had investigated use of iES in patients with no ability to contract or very weak PFM [
8]. They compared iES undertaken once a week for 8 weeks, with PFMT with facilitation techniques, with and without pelvic tilt. Intravaginal ES was found to be the least effective intervention. Subjects in the other two groups demonstrated a better ability to voluntarily contract their PFM following the intervention period and reported greater improvements on self-reported urinary incontinence. It is possible that iES was less effective as subjects in this group were specifically instructed not to voluntarily contract their PFM.
This is supported by a past consensus statement concluding that electrically stimulated muscle contractions alone are less effective at improving muscle strength compared with voluntary contractions [
25].
It is currently not known what the optimal ES parameters are for women who have difficulty with voluntarily contracting their PFM [
26]. Use of standardised protocols for specific conditions like SUI are not always optimal. The present study designed a protocol based on past studies that have undertaken iES [
8,
27,
28] and clinical experience. Electrical stimulation parameters were individually tailored with the aim of achieving a good visible indrawing of the perineum that was considered comfortable for the participant, and a standardised protocol implemented for progression of therapy. To our knowledge, our study is the first to have undertaken iES of PFM on a daily basis over many months. Our findings of very good participant adherence and very few side effects supports the feasibility and tolerance of our ES protocol. A future large RCT should take into consideration the possibility that daily iES could irritate the vaginal lining.
The strengths of this study include; Randomization to intervention group; use of trained, blinded assessors; reproducible, individually-tailored intervention protocols; very good participant adherence; feedback that all subjects would recommend their therapy type to others; and use of reliable and valid manometry measurements. Whilst measurement of the strength of a PFM contraction using vaginal palpation [
17] has demonstrated moderate to very good intra-examiner reliability, inter-examiner reliability has been found to be only fair [
29]. Vaginal palpation of the PFMs is a commonly used method to assess PFM function in physiotherapy. However, manometry has been found to be more reliable, valid and sensitive to measure muscle strength, and there is often a poor agreement between testers when comparing vaginal palpation with manometry (45–47%) [
16,
29]. Our study also clearly describes how facilitation techniques were undertaken with PFMT during treatment sessions.
A limitation of all pilot studies, including ours, is the small sample size. As anticipated, there were too few participants to be able to determine if iES is a more effective treatment than PFMT in women with weak PFM. Our primary aim was to determine how many participants we would require to detect a difference between groups in a full-scale RCT. Had the differences between groups been greater, we would not have required as many as 95 subjects in each group in a future study. If we had included a non-treatment control group, we may have found that the two intervention groups achieved a significant improvement compared to the control group. In a future large-scale RCT it may also be beneficial to record stage of POP using POP-Q.
Conclusion
This study demonstrates that both iES and PFMT are feasible interventions in women with weak PFM. Women in both groups increased their PFM strength and reported improvements in symptoms of POP and urinary incontinence. As anticipated, it was not possible to determine if iES was a more effective therapy given the small sample size. To detect a difference between groups, we would have required 95 women in each group.
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