Bladder Neck Moves in a Correlated Manner During Gluteal Muscle and Pelvic Floor Muscle Contractions: Gluteal Muscle Contraction as Easily Confirmable Pelvic Floor Muscle Training

Urinary incontinence is defined as the complaint of involuntary leakage of urine, of which incidence is increased with aging. It is well known that gluteal muscle （GM） and pelvic floor muscle （PFM）contract simultaneously; the former serves as extension or external rotation of the hip joint, while the latter does as the supportive function of abdominal and pelvic organs. We have shown that bladder neck movement analyzed by magnetic resonance imaging （MRI） was useful for understanding the beneficial effects of pelvic floor muscle training （PFM-training）on the prevention of urinary incontinence. In the current study, we hypothesize that （i） bladder neck movement accompanied by the GM contraction can be a landmark to evaluate the beneficial effect of PFM-training on urinary incontinence and （ii） hopefully, the GM contraction that can be identified easily from the body surface might be substituted for the PFM contraction. For this purpose, using cine MRI, the difference in bladder neck movement was compared between the GM and PFM contractions. Twenty-four women including 3 nulliparous and 21 primiparous women with the mean age of 29.5 years were included. Using a mid-sagittal section of cine MRI, the difference in height or position （anteroposterior position） of bladder neck was analyzed among the groups at rest, during GM and PFM contractions. In this study, the maximum change of bladder neck movement induced by involuntary GM was almost the same as that induced by PFM contraction. Likewise, during the first 10 seconds of the scanning periods, the longitudinal change of bladder neck movement did not show any significant difference between the GM and PFM contractions. These findings place an emphasis on the potential benefit of the GM contraction during PFM-training against urinary incontinence in the routine clinical setting. Our approach of applying the tactile GM contraction to the PFM-training program can surely pave the way for establishing the practical method to overcome the uncomfortable urinary incontinence that is more likely to affect the routine quality of life.