## 4 Discussion  
This systematic review's results showed that women after PFM exercises with BF had a statistically significant improvement in muscle strength and other PFM parameters (such as endurance, muscle function and precontraction), severity of incontinence, QoL and social life. These results were mostly based on women with SUI and MUI and, to a lesser extent, on women with UUI. In five studies, out of which four were of moderate-quality [27; 28; 29; 32] and one of high-quality [34], it was shown that PFM exercises with BF had a statistically significant improvement in muscle strength compared to PFM exercises alone. Four out of these five studies included women with SUI [27; 28; 29; 34] and in only one study [32] the sample consisted of women with SUI, MUI and UUI. In the remaining four studies [24; 30; 31; 33], which did not state a significant difference between BF and non-BF groups, the sample consisted of women with SUI or MUI. This could lead to the conclusion that the intervention was more effective in women with SUI for the parameter of PFM strength. The results of our systematic review were in agreement with another experimental study [36], which found that PFM exercises with BF had a significantly positive impact on PFMs in comparison to a baseline evaluation. In another study [37], it was shown that there was a significant improvement in PFM strength in both BF and non-BF groups. In the systematic review of [PERSON] et al. [21], PFM exercises with BF were not more effective in terms of muscle strength than other ones (such as isolated PFM exercises, electrostimulation and no training). However, the included studies mostly consisted of low-methodological-quality RCTs, which negatively influenced the results. In contrast, this systematic review consisted mostly of moderate-methodological-quality RCTs [24; 25; 27; 28; 29; 30; 31; 32] and two high-quality ones [26; 34]. In the study of [PERSON] et al. [27], which was of moderate quality, there was a statistically significant and'speedy' improvement in pelvic floor muscle strength and a reduction in the severity of incontinence in the BF group compared to the non-BF group after the 4-week reassessment. Interestingly, this faster improvement in the BF group after four weeks of intervention was also seen in [PERSON] et al. 's study [33]. An explanation for this fast response could be that the biofeedback provided an easy and accurate identification of the PFMs, thus, facilitating the correct contraction of women who were unable to consciously locate or feel the muscles in order to perform the exercises. Interestingly, it was found that approximately 30% of women were not capable of performing isolated pelvic floor contractions after written or verbal guidance [38; 39]. Thus, it may be that the BF training during these early stages of PFM rehabilitation may have been beneficial in promoting a faster improvement in muscle tone, better neuromuscular function and also better urethral closure. One more possible explanation could be that an early improvement gave additional motivation to patients, who were then encouraged to continue the exercises [27]. It is worth noting that positive results from biofeedback may also have been due to the subjects having more interaction with the therapist during the exercise [40]. Such a fast improvement was also shown in the study of [PERSON] et al. [29], who also evaluated the participants after 4 weeks of intervention and yielded better results for maximum voluntary contractions and muscle precontractions in the BF group compared to the non-BF one. Incontinence symptoms improved in most studies. Even though, in some studies, the results were in favor of the BF group [27; 28; 30; 32; 34], in other studies, the results were similar between the groups [25; 26; 30; 31; 33; 34].