In the one study the biofeedback component in the group doing PFM training increased the sEMG amplitude of the PFM significantly more than in the group doing the PFM training alone [1].
The aim of our study was to compare in a sample of women with urodynamically diagnosed stress urinary incontinence the bioelectrical signals (amplitudes) of the pelvic floor muscle (PFM), rectus abdominis (RA) and internal oblique (IO) obtained in supine and standing positions before and after two months of electromyographic (sEMG) biofeedback added to pelvic floor muscle training, to determine differences in muscle activity [2]. The secondary aim was to compare changes in the results of urodynamic tests [3], voiding diary vis-à-vis baseline values.

The study (non randomized clinical trial) involved women with stress urinary incontinence (n=15). 
The mean sEMG amplitude of the pelvic floor muscle was tested during two trials (5 repeated short contractions and 5 repetitions of 10-second voluntary contractions) at two time points. Voiding diary and urodynamic tests were used to asses all study participants at the same two time points. The study protocol was approved by the Bioethics Committee. Measurements were performed under standard testing conditions, the same for all subjects. Participants were presented with a comprehensive description of the aim and methods of the study and gave their written consent to participate. 
The sEMG of the pelvic floor muscles was recorded using an endovaginal probe. Two surface electrodes were located along muscle fibers of the rectus abdominis (RA) and two electrodes of the internal oblique (IO) according with the standards for surface EMG. Training sessions with visual biofeedback were held over two months, 3 times a week (24 training sessions altogether). At the outset of sEMG biofeedback training each participant performed maximal voluntary contraction (MVC) of the pelvic floor muscles. The MVCs values were used as a reference threshold for the training. Phasic contractions lasting 3 second, with 6 second relaxation, increased progressively every two weeks from 21 repetition (7 contraction/relaxation repetition in 3 series) to 60 repetition (12 contraction/relaxation repetitions  in 5 series) at 80% of the EMG MVC. Sustained contractions lasting 10 second, with 10 second relaxation time, increased progressively every two weeks from 35-120 repetitions (15 contractions/relaxation repetition in 3 -8 series) at 60% of the EMG MVC.

The two-way interaction time point x position proved not significant for mean sEMG amplitudes during short PFM contractions, and the post-hoc analysis did not show mean amplitudes recorded in the supine position at the two time points to be significantly different. Similary, the post-hoc analysis did not show mean amplitudes recorded in the standing position at the two time points, and between position at time point 1 ant time point 2 to be significantly different.
 Two-way interactions time point x position proved not significant for mean amplitudes obtained during 5 repetitions of 10-second voluntary PFM contractions. The two-way interaction time point x position were not significant for sEMG of internal oblique (IO) and of rectus abdominis (RA) obtained during short and 10-second voluntary PFM contractions (Table 1).
Quantitative variables obtained from filling and voiding cystometry performed before and after two months of sEMG biofeedback training were statistically significant different (Table 2).
The number of incontinent episodes recorded at baseline and after training were significantly different.

The sEMG activity of the pelvic floor muscles was not found to be statistically significantly different in the study participants after 2 months of EMG biofeedback- assisted pelvic floor muscle training compared with its baseline values. Changes in the results of voiding diary (reduction of incontinence episodes) and urodynamic tests were statistically significant.

The sEMG biofeedback training did not significantly improve the bioelectrical activity of the pelvic floor muscles, but it was shown to be capable of relieving the symptoms of urinary incontinence.

Aukee  P, Immonen P, Penttinen J, Laippala P, Airaksinen O. Increase in pelvic floor muscle activity after 12 weeks' training: a randomized prospective pilot study. Urology 2002, 60,6:1020-1023
Krhut J, Zachoval R, Rosier PFWM, Shelly B, Zvara P. Electromyography in the assessment and therapy of lower urinary tract dysfunction in adults. Neurourol Urodyn. 2017 Apr 18. doi: 10.1002/nau.23278.
Schäfer W, Abrams P, Liao L, Mattiasson A, Pesce F, Spangberg A, Sterling AM, Zinner NR, van Kerrebroeck P. International Continence Society. Reliability ICS Good urodynamic practices: uroflowmetry, filling cystometry, and pressure-flow studies. Neurourol Urodyn. 2002, 21,3,:261-274