Effects of wearing supportive underwear versus pelvic floor muscle training or no treatment in women with symptoms of stress urinary incontinence: an assessor-blinded randomized control trial Abstract Introduction and hypothesis In our previous single-arm pilot study, we reported that ready-made supportive underwear (shaper) was effective in elevating the bladder neck and reducing urinary incontinence (UI) symptoms. The aim of this study was to determine the effects of wearing a shaper compared with pelvic floor muscle training (PFMT) at home using a training compact disc with music, or no treatment, in an assessor-blinded randomized control trial, on reducing UI symptoms. Methods Participants aged 30–59 years with symptoms of stress urinary incontinence were randomly assigned to three groups: the shaper group, PFMT group, and no treatment group. The UI episodes/week and the Japanese version of the International Consultation on Incontinence Questionnaire Short-Form were compared between the baseline and the 6th or 12th week of the intervention period. Results Eighty-nine women who completed the 12-week intervention period were analyzed. After the 12-week intervention period, the improvement rate in UI symptoms (ratio of the case number in which the UI episodes/week decreased at least 50% from the baseline) was 73.3% (22/30 women) in the shaper group, 74.2% (23/31 women) in the PFMT group, and 25.0% (7/28 women) in the no treatment group. The improvement rate in UI symptoms in the shaper and PFMT groups was significantly higher than that in the no treatment group (both P < 0.001). Conclusions Wearing supportive underwear (shaper) was almost as effective as PFMT at home in reducing UI symptoms.