Mechanisms for pelvic floor muscle training: Morphological changes and associations between changes in pelvic floor muscle variables and symptoms of female stress urinary incontinence and pelvic organ prolapse—A narrative review

Abstract Introduction Today there is Level 1, recommendation A for pelvic floor muscle training (PFMT) to be effective in treatment of stress urinary incontinence (SUI) and pelvic organ prolapse (POP). However, the mechanisms of action are discussed. The aim of the present overview was to give an update of studies evaluating the effect of PFMT on pelvic floor morphology and associations between changes in PFM strength and symptoms of female SUI and POP. Materials and Methods This was a narrative review retrieving studies from systematic reviews of PFMT for SUI and POP. In addition, an open search on PubMed with the search terms PFMT and morphology was conducted. Both randomized controlled trials (RCTs) and pre–posttest design studies were included. PEDro rating scale (0–10) was used to assess risk of bias. Results Ten studies were found reporting on morphological changes after PFMT. The four RCTs had PEDro score between 5 and 8/10. The studies found significant higher bladder neck position and narrower levator hiatus dimensions, thicker external urethral sphincter, increased cross‐sectional area of PFM, improvement in PFM tears and blood flow. Twenty studies analyzed associations between changes in different PFMT variables and SUI and POP. Eleven studies found a positive weak to moderate association and six studies reported no association. Studies comparing responders and nonresponders to PFMT found statistically significant better PFM variables in responders. Conclusion PFMT can change pelvic floor muscle and external urethral sphincter anatomy. This contributes to the understanding on how PFMT can be effective in prevention and treatment of SUI and POP.