Influence of voluntary pelvic floor muscle contraction and pelvic floor muscle training on urethral closure pressures: a systematic literature review

Zubieta M, Carr RL, Drake MJ, Bo K: Int Urogynecolo J, 2015.  DOI 10.1007/s00192-015-28856-9; Online ISSN 1433-3023.
Ann Dunbar PT, DPT, MS, WCS
June 8. 2016

Introduction:  Though pelvic floor m training (PFMT) is effective for treatment of stress urinary incontinence (SUI) (Level I evidence), how this works is not clear. Several theories are presented including (1) PFM morphology is altered; (2) PFMT prevents bladder and urethral descent with activities increasing intra-abdominal pressure; (3) PFMT increases strength of a voluntary pre-PFM contraction and appears to reduce downward movement of bladder neck with cough (ie the Knack) ;  PFMT facilitates unconscious, automatic firing of PFM, increasing maximal urethral closure pressure (MUCP) during increases in intra-abdominal pressure.

Primary Aims:  (1)” to determine the incremental increase in MUCP elicited by a single PFM contraction (augmented MUCP); (2) to evaluate the effect of PFMT on both resting and augmented MUCP.”

Study Format:  Systematic Literature Review

Methods:   Systematic review using PUBMED with advanced search on PEDro.  PFMT was defined as sets of PFM exercises over time, including use of weighted cones and biofeedback. Exclusion criteria listed in study. Studies were classified according to preset criteria (experimental studies and clinical trials listed in Tables 1 and 2 respectively).  Authors rated clinical trials according to PEDRO scale and also followed PRISMA (set of items for reporting systematic reviews). 

Results: 

• Experimental Studies: See Table 1. Found 21 studies between 1982 and 2012 investigating augmented MUCP. Prior to 2002, there was a lack of consensus with urodynamic (UD) methodology including definition for concept of urethral pressures as well as standardization of measurement methodology. Some studies, authors did not clearly state whether patients correctly performed PFM contractions, either before or during UD studies.
• Augmentation of MUCP by PFM Contraction: 
• MUCP incremental increase during PFM contraction in healthy women ranged from 8 to 47.3 cm water
• MUCP incremental range in women with UI varied from 6 to 23.5 cm water
• Three studies comparing women with and without SUI found higher MUCP in continent women by 7 to 8 cm water however only 2/3 found significant difference  (p<0 .01="" o:p="">

Authors report on a collection of studies with varied results such as:

• Studies including women with possible injuries to pelvic floor reported varied results, some reported reduction in MUCP during PFM contraction compared with resting measurement and some reported no significant difference
• Found alterations in MUCP may occur due to other factors such as downward pressure caused by abdominal straining
• Age negatively correlated with both augmented MUCP and MUCP
• Unable to determine where the greatest increase in closure pressure could occur along the urethra during a PFM contraction despite assessing for this at different points

• PRMT Clinical Trials

• Authors identified nine trials reporting urethral pressure profiles as outcome of PFMT 1987-2008 (three RCTs, one nonRCT, five pre/post designs; PEDro scores for three RCTs >5; six defined SUI by UDTesting; six confirmed PFM contraction by vaginal palpation
• PFMT regimes varied greatly across nine studies (time ranged 6 wks to 12 mo; five reassessed PFMT affect after 3-4 months; supervision from PT or nurse varied from 2x/wk to 1 assessment then subject on her own with HEP; exercise protocol varied from 5-10 contractions every 30 minutes daily in 1987 to 8 to 12 reps 3x/day; two studies didn’t report whether subjects were encouraged to do ex. at home
• Effect of PFMT on resting MUCP
• Two studies found statistically significant increase in resting MUCP (Bo, 1999 comparing intensive PFMT group to HEP only and Benvenuti, 1987 had no control group)
• Effect of PFMT on augmented MUCP
• Seven studies assessed MUCP with PFM contraction with results varying from  - 0.1 cm water to 25 cm water
• Effect of PFMT on other Urethral Pressure Profilometry (UPP)
• Other measures studied included functional urethral profile length (five of pre/post-test design) and cough-pressure transmission ratio without conclusive findings due to wide variability in study methodologies

Discussion

• Authors conducted systematic review assessing influence of voluntary PFM contraction on MUCP and reviewed studies investigating effect of PFMT on both MUCP and augmented MUCP
• Inclusion criteria were broad to capture studies investigating single PFM contraction as well as PFMT on MUCP across a broad population of women, healthy and SUI or MUI
• Methods of UPP differed substantially and PFMT protocols were widely variable so pooling of results for meta-analysis was not valid

Experimental Studies

·         Results demonstrate wide variance in augmented MUCP (from 8 to 33 cm water in healthy women and 7 to 8 cm water in women with UI)

·         Authors investigated possibility of being able to make a meaningful prediction regarding the minimum augmented MUCP needed to maintain continence however were not able to do so because (1) too few studies comparing healthy/UI women and (2) methodologies for UPP were varied (authors describe varied techniques and varied results produced but do conclude that women with SUI are consistently identified as having a lower MUCP)

·         Based on results of analysis, authors suggest additional research needed on the influence of age on augmented MUCP

·         Authors discuss difficulty of determining impact of PFM contraction on MUCP where methodology did not assess for ability to contract PFMs correctly (half of the studies reviewed did not report whether this assessment was carried out)

·         Several studies included women with injury to PFMs and results are not clear as to how this affects MUCP

      Clinical Studies

• Results suggestive of PFMT increases augmented MUCP (increment ranging from 4 to 25 cm water) though wide variation as to the extent of the effect so authors conclude they were unable to draw firm conclusions (suggest standardizing UD methodology, PFM assessment, compliance with PFMT and outcome reporting)
• Not possible to conclude what minimum increase in pressure would be needed to achieve continence
• Considerations making it difficult to draw firm conclusions include details of PFMT such as confirmation of correct contraction, adherence to program, training duration, dosage
• Adapting to strength training appears to move linearly over the first 6 months of training yet only 3 studies carried out over this period
• Two studies used training regimes recommended by ACSM:  three sets daily of 8 to 12 reps
• Considerations making it difficult to draw firm conclusion related to UPP as a diagnostic test
• Need to utilize agreed-upon methodology for UPP, UPP during PFM contraction and MUCP before and after PFMT

Conclusion

• Results of this analysis of related studies demonstrate  that, at this point, minimal evidence exists to support theory that PFMT will produce a significant increase in MUCP however UPP and PFM strength are challenging variables to measure with objective reliability
• Degree of augmentation to MUCP provided by PFMT varies greatly
• Evidence did suggest PFMT increases augmented MUCP though drawing firm conclusions is clouded by study methodologies