There is level 1A evidence for pelvic floor muscle training (PFMT) to be the first line treatment for stress and mixed urinary incontinence in women (1) . However, it has also been hypothesized that contraction of other muscle groups such as abdominals (m.rectus abdominis and the transversus abdominus muscle (TrA), hip adductors and external rotators could  be used to activate the PFM (2).
The aims of the present study were firstly to assess whether contraction of muscles other than the PFM, activates the PFM sufficiently to provide a training effect, and secondly to assess the efficacy of a novel intra-vaginal pressure sensor (FemFit®) to simultaneously measure PFM contraction and intra-abdominal pressure (IAP) during all exercises.

This was a cross-sectional experimental study using the FemFit® (3). The FemFit® is a prototype pressure sensor array,  designed to fit  the length of the vagina. The device is 80mm in length with eight evenly spaced pressure sensors encapsulated in a soft, medical grade silicone. The most distal sensors (7 & 8 ) are placed in the posterior fornex enabling measurment of intra-abdominal pressure (IAP). The remaining sensors will measure activation of other muscles, predominately the pelvic floor muscles.  A convenience sample of 21 experienced pelvic floor physiotherapists, were invited to participate. Exclusion criteria were an inability to contract the PFM, pregnancy, being less than 12 months postpartum, > Stage 2 prolapse, and SUI > once a week. All participants self-inserted the FemFit® with the instruction: ‘insert as you would a tampon’. Once the device was in-situ, ability to contract the PFM was assessed by visual observation of the perineum, and in-drawing of the FemFit®. The procedure started with a 30 second relaxation followed by three maximal contractions of the PFM. Three contractions of the following muscle groups were then performed in random order: internal rotation of the hips, external rotation of the hips, abduction of the hips, adduction of the hips, contraction of the gluteal muscles, pelvic tilt (primarly M. Rectus abdominis), indrawing (primarly TrA),abdominal crunch (primarly M. Rectus abdominis), deep inspiration and deep expiration. The procedure concluded with 30 second relaxation  and then a double cough. All activities were performed in the supine position. Maximum pressures were determined for each pressure sensor, for each exercise/maneuver. The maximum pressures were then averaged across the three repetitions of each exercise. The sensors measuring the highest pressures, during the PFMC‘s  were deemed to represent the location of the pelvic floor. Sensor 8 represented abdominal pressure. Wilcoxon paired tests were used to ascertain the difference in PFM pressure between exercises, and if there were differences in the pressures between the PFM sensors and the abdominal sensors for each exercise. Bonferroni correction was applied setting α = 0.005.

Twenty-one women completed the procedure, with two sets of data not available for analysis due to issues with data collection. Mean age of the participants were 43.7 years (SD ±11.3) range 26 – 62 years. Mean BMI was 22.4 kg/m2 (SD ±3.2 kg/m2). Sixteen participants were parous, with a median parity of 2. Mean PFM pressure for PFMC was 16.29 mmHg (SD ±12.28) range 4.21 – 40.69 mmHg, but only 9 women had a pressure increase of > 10 mmHg. PFM pressure was greater during a PFMC compared to all other exercises, except for curl-ups and cough (Table 1). However, for the curlup exercises we observed pressure higher than PFMC pressure in only 5 participants, and lower in 14.
Table 1:Estimated pressure difference between PFMC pressure and PFM pressure for all exercises. 

Wilcoxon tests showed a significantly higher PFM pressure than IAP for PFMC, internal rotators and gluteals (p < 0.001) (Fig 2).
Fig.2: Box and whisker plot (Medians, 25%, 75% quartiles) for PFM  and IAP for all exercises.

PFM pressure during a PFMC was more than that measured for any other exercise, except for cough and curlups. There is a possibility co-contraction of the PFM occurs during a curlup. However, the magnitude of the difference between PFM pressure and IAP for curlups is trivial. The magnitude of the difference from a PFMC is significant.  It was surprising that more than half the physiotherapists had a very weak PFMC.

Co-contractions of the PFM during contraction of other muscle groups are mostly minor. Targeted PFMC should still be recommened. The FemFit was able to distinguish between pressures developed in the region of the pelvic floor muscles and IAP.

Dumoulin C, Hay-Smith J, Berghmans B, Burgio K et al. Adult Conservative management. In: Abrams P, Cardozo L, Wagg A, Wein A (eds) Incontinence. 6th International Consultation on Incontinence, Tokyo Paris, 2016. Committee 12; 1443-1628. Health Publications Ltd, Portsmouth.
Bø K, Herbert R: There is not yet strong evidence that exercise regimens other than pelvic floor muscle training can reduce stress urinary incontinence in women: A systematic review. J Physiotherapy, 59,3: 159-168 2013
Schell A, Budgett D, Nielsen P, Smalldridge J, Hayward L, Dumoulin C, et al. Design and development of a novel intra-vaginal sensor array. Neurourol Urodyn. 2016;35(4):S355-6.