On pelvic floor muscle function and stress urinary incontinence: Effects of posture, parity and volitional control.

Abstract

One-tenth, and in the elderly one-third, of women experience stress urinary incontinence (SUI), unwanted urine loss occurring during sudden rises in intra-abdominal pressure (such as a cough). The pelvic floor muscles (PFM) are thought to prevent urine leaking from the bladder. Five studies were conducted to examine PFM function during supine and upright activities associated with SUI. In Study I a Graduated Strength Training PFM exercise protocol was developed which resulted in significant PFM strength improvement with markedly fewer contractions than are traditionally prescribed. The protocol's efficiency was shown to be improved by incorporating PFM motor control skill acquisition into the graded exercise assignment. In Study II, use of a precisely-timed PFM contraction, termed the Knack, was hypothesized to reduce SUI. To test this hypothesis, the amount of urine leaked during a cough was quantified by measuring the wetted area of a brown paper towel (The Paper Towel Test). The results at one week post-instruction demonstrated that use of the Knack in a medium strength cough significantly reduced mean urine leakage by an average 86% over that measured without use of the Knack ($p<.005$). The corresponding mean decrease for a deep cough was 60% ($p=.011$). These findings contrast with the current unwritten assumption that effectiveness of PFM therapy is dependent upon a three month strengthening program. In Study III, a new instrument designed to measure distal vaginal pressure (DVP) adjacent to the midurethra was shown to perform reliably during selected dynamic activities often associated with SUI. In Studies IV and V this instrument was used to quantify, for the first time, how DVP varied with supine and upright postures, and after vaginal birth. Results show significant increases in static and dynamic DVP pressures in upright activities compared with those in the supine posture. Mean DVP was significantly reduced in SUI women. Continent primiparous women developed significantly smaller mean DVP in voluntary PFM contractions than did continent nulliparous women. Conclusion. These studies suggest immediate ways to improve the efficacy of behavioral interventions aimed at treating mild-to-moderate SUI. They also give new insights into the postural role of the PFM.