Pelvic-floor muscle (PFM) training is recommended as first-line treatment for stress urinary incontinence (UI), in women.[1] Recently, approaches such as Abdominal Hypopressive Technique and Low Pressure Fitness have been proposed as alternatives to PFM training for the treatment of stress UI. These approaches involve a diaphragmatic aspiration (an apnea) with or without a specific body posture. Theoretically, the execution of these techniques would result in a decreased abdominal pressure leading to a reflex activation of the abdominal and PFM, thereby increasing vaginal force closure and reducing UI. To our knowledge, no mechanistic studies have compared the effect of a diaphragmatic aspiration, with or without a specific body posture, to PFM maximal voluntary contraction in regard to the pressure distribution along the vaginal cavity of women with stress UI.

The aim of this study was to compare intravaginal pressure profiles in women with stress UI during three tasks: a PFM maximal voluntary contraction, a diaphragmatic aspiration alone and a diaphragmatic aspiration associated with a body posture described in the Low Pressure Fitness approach (the Venus posture).

We conducted an observational cross-sectional study. Participants were recruited through newspapers, advertisements in community centers, web and social media initiatives. Eligible participants were community-dwelling women, age 18 years and over, who reported at least three episodes of urine loss per week during the preceding three months, as noted in the 7-day bladder diary. Stress UI was confirmed using the validated Questionnaire for Incontinence Diagnosis. Exclusion criteria were: other UI type (urge or mixed UI), pregnancy, pathology/risk factor or medication likely to interfere with the study such as cardiac and respiratory conditions or high blood pressure.  

The intravaginal pressure profile was assessed using the FemFit®, an 80 mm intra-vaginal pressure sensing device comprising of an array of eight independent pressure sensors, separated by nine mm gap. The device is thin (4mm) and flexible, enclosed with a soft biocompatible silicone. This device was previously tested for reliably and validity.[2] Pressure data was transmitted, via Bluetooth to an Android tablet for data logging and real-time display for user feedback.

Before an assessment session the FemFit® was disinfected and covered with a condom. A trained physiotherapist taught the participant how to effectively contract the PFM via vaginal palpation. Standardized instructions were then given via a short training video recorded by an expert (JV) on how to execute a diaphragmatic aspiration alone and a diaphragmatic aspiration associated with the Venus posture. Both tasks were practiced under supervision, prior to pressure measurement. The FemFit® was then inserted into the participant’s vaginal cavity in an anterio-posterior axis by the physiotherapist. The device position in the vagina was verified after every task.

Data was acquired at rest and during three trials of each of the three tasks, in the standing position. Tasks were consecutively executed with a 15 second rest-period between each trial and task, to avoid fatigue. For each task, the peak pressure, defined as the maximum pressure achieved across the eight sensors and the peak pressure location, were identified. Delta pressure was calculated from the rest task (peak pressure – rest pressure). As the distribution of these outcomes exhibited violation of the normality assumption, main analyses relied on non-parametric tests (Friedman test and Wilcoxon test).

From April 2019 to August 2019, seventeen participants were recruited. The mean age of the participants was 52 years (SD 11.73), mean BMI was 29.4 kg/m2 (SD 7.05), median parity was 2, mean duration of UI symptoms was 8 years (SD 6.8) and median leakage episodes per week was 11 (Q1= 7; Q3= 27,5).  Data from two participants were not usable for analysis. 

Figure 1 shows the mean pressure profile for each task. Visually, each task produced a specific vaginal pressure profile with both diaphragmatic aspiration tasks producing pressures lower than the resting pressure. The mean peak pressure was 87% and 82% higher during PFM maximal voluntary contraction task than during the diaphragmatic aspiration and diaphragmatic aspiration with the Venus posture tasks respectively (z = -2.98, P < 0.01; r (effect size) = 0.86 for diaphragmatic aspiration and z = -2.84, P < 0.01; r = 0.86 for diaphragmatic aspiration with Venus posture). No significant difference was found between the two diaphragmatic aspiration tasks (z = -0.63, P > 0.01; r = 0.18) (Figure1). Compared to rest, the mean amplitude of the peak pressure was significantly higher for maximal PFM voluntary contraction task (z = -3.30, P < 0.01; r = 0.88) but not for the two other tasks (Figure 2). As for the peak pressure location, no significant difference was found between the three tasks χ2 (2, n= 11) = 5.71, P > 0.05, with peak pressures occurring mostly between sensor 3 and sensor 6.

To our knowledge this is the first study to compare the effect of a diaphragmatic aspiration with or without a specific body posture to a PFM maximal voluntary contraction using an intravaginal pressure profile measuring instrument in women with stress UI.

All three pressure profiles were different. Our results show that PFM maximal voluntary contraction task produced a significantly higher peak pressure compared to both alternative tasks. PFM maximal voluntary contraction would therefore lead to greater vaginal closure force, an important component in maintenance of continence during effort. In line with our results, Stupp et al. [3] found higher muscle activation patterns during a PFM maximal voluntary contraction than during a diaphragmatic aspiration, using intravaginal EMG measurements. 
Accordingly, only during the PFM maximal voluntary contraction task a significant higher peak pressure could be observed when compared to the rest condition. In contrast during both diaphragmatic aspiration tasks, the peak pressure achieved was not different than the one achieved at rest, questioning the proposed mechanism of action of the hypopressive approach with or without a specific body posture in producing a significant reflex activation of the PFM musculature. Finally, peak pressure location along the length of the vagina was not significantly different between tasks but amplitude pressures were, once again questioning the proposed mechanism of action of the hypopressive approach compared to direct PFM activation.

After initial training, diaphragmatic aspiration and the diaphragmatic aspiration associated with Venus posture produced lower peak pressure than PFM maximal voluntary contraction. Furthermore, only a maximal voluntary PFM contraction produced higher intravaginal peak pressures than the ones observed at rest. For both of the aspiration tasks the intravaginal peak pressure achieved was not different than the ones observed at rest. Adding a posture did not appear to add value to diaphragmatic aspiration. More research is needed to better understand mechanism of action of Abdominal Hypopressive Technique and Low Pressure Fitness approaches in the long term and in other body positions.

Neurourology & Urodynamics, 2018;37(7):2271-2272.https://doi.org/10.1002/nau.23551.
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