Pelvic floor muscle exercise for the treatment of female stress urinary incontinence: II. Validity of vaginal pressure measurements of pelvic floor muscle strength and the necessity of supplementary methods for control of correct contraction

The present investigation comprises three methodological studies concerning vaginal pressure measurements of pelvic floor muscle (PFM) strength. Vaginal pressure was measured by a balloon (6.7 ± 1.7 cm) connected by a catheter to a pressure transducer. The balloon was placed with the middle of the balloon 3.5 cm inside the introitus vagina. In fourty‐seven women, mean age 44.9 years (24–64), observation of movement of the vaginal catheter during PFM contraction verified 7 inconclusive results from perineovaginal palpation and was the most valid way to distinguish between correct and incorrect PFM contraction. Vaginal pressure rise was obtained regardless of correct or incorrect PFM contraction, showing that vaginal pressure is not specific for PFM contraction. However, as the action of the PFM is elevation, a simultaneous inward movement of the vaginal catheter is present only during correct PFM contraction. Degree of influence of various muscle groups on vaginal pressure was investigated in 14 women using two different balloons, one having a silicone reinforcement of the tip. It was found that the median contraction value of muscles other than the PFM did not exceed contraction of PFM alone. No significant difference was observed using the two types of balloons. In three physical therapists EMG activity of the lower m. rectus abdominis was recorded during maximal PFM contractions. A rise in EMG activity always occurred during maximal contractions even if the women actively tried to relax the abdominal muscles. It is concluded that vaginal pressure measurement of PFM strength is valid with simultaneous observation of inward movement of the balloon catheter. Vaginal pressure rise due to simultaneous contraction of other muscles is probably not larger than pressure rise due to intended PFM contraction. Reinforced balloon tip will not change pressure recording, and rise in EMG activity of lower abdominal muscles seems unavoidable during maximal PFM contraction.