Pelvic floor muscle strength and response to pelvic floor muscle training for stress urinary incontinence.
Several randomized controlled trials have demonstrated that pelvic floor muscle training is effective to treat stress urinary incontinence. The aim of the present study was to compare muscle strength increase and maximal strength in responders and non-responders to pelvic floor muscle training. Fifty-two women with urodynamically proven stress incontinence who had participated in a six months randomized controlled trial on pelvic floor muscle training, mean age 45.4 years (range 24-64), participated in the study. The women were classified as responders and non-responders based on a combination of five effect variables covering urodynamic measurement, pad test with standardized bladder volume, and self-reports. Pelvic floor muscle strength was measured with a vaginal balloon connected to a fiber optic micro tip transducer (Camtech AS, Sandvika, Norway). There was a positive correlation between improvement in PFM maximal strength and improvement measured by leakage index (r = 0.34, P < 0.01), and reduction in urinary leakage measured by the pad test (r = 0.23, P = 0.05). The total sample of 52 women comprised 21 responders, 18 unclassifiable, and 13 non-responders. There was a statistically significant difference in maximal strength after the training period between responders and non-responders; 24.0 cm H2O (95% CI:18.1-29.9) versus 12.7 cm H2O (95% CI: 6.8-18.6) P < 0.001), and strength increase; 14.8 cm H2O (95% CI: 8.9-20.7) versus 5.0 cm H2O (95% CI: 2.6-12.6), respectively (P = 0.03). There was a positive relation between both pelvic floor muscle strength increase and maximal strength, and improvement of stress urinary incontinence.