Force and stiffness of the pelvic floor as function of muscle length: A comparison between women with and without stress urinary incontinence.
OBJECTIVE
To compare passive and active mechanical properties in the pelvic floor as a function of tissue length in continent and incontinent parous women.


METHODS
Twenty-four parous continent and 21 parous incontinent women were examined with an intravaginal device. Passive and active force/stiffness were measured by increasing the transverse diameter of the vagina. To allow a more accurate comparison between groups, measured forces were normalized with respect to bodyweight, that is, force/bodyweight.


RESULTS
In both groups passive and active forces increased as a function of the increase in length of the pelvic floor tissues. No difference was found between the groups according to passive forces (P = 0.646), but active force was significantly higher (P = 0.030) in the continent group when normalized for bodyweight. There was an almost linear increase in normalized passive stiffness in the range tested. No differences were found between the groups (P = 0.855). Normalized active stiffness was significantly reduced in the incontinent group (P = 0.021).


CONCLUSIONS
This study indicates that both active force development and active stiffness in the pelvic floor tissues are significantly reduced in incontinent women, whereas the passive resting mechanical forces in the pelvic floor tissues in both groups are not different.
Verelst
M
M
Institute of Clinical Medicine, Department of Obstetrics and Gynaecology, University of Tromsø and University Hospital of Tromsø, Norway. margareta.verelst@unn.no
Leivseth
G
G
D000328:Adult; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008875:Middle Aged; D053580:Muscle Strength; D018482:Muscle, Skeletal / Q000033:anatomy & histology / Q000502:physiology* / Q000503:physiopathology; D010298:Parity; D017773:Pelvic Floor / Q000033:anatomy & histology / Q000502:physiology* / Q000503:physiopathology; D011247:Pregnancy; D012016:Reference Values; D014550:Urinary Incontinence, Stress / Q000503:physiopathology*