Is pelvic floor loading in female runners associated with post-run changes in pelvic floor morphometry or function?

To investigate whether, among female runners, transient changes in pelvic floor morphometry, pelvic floor muscle (PFM) function, or pad weight gain observed after a standardised running protocol are associated with the exposure of the pelvic floor to loading during the run.

Adult female runners with (n = 19) and without (n = 19) running-induced stress urinary incontinence (RI-SUI) completed a 37-min treadmill-based running protocol with a pressure sensor placed in the posterior fornix of the vagina and a triaxial accelerometer adhered to the pelvis, and an incontinence pad adhered to their undergarment. Pelvic morphometry and PFM function were assessed before and after the run using transperineal ultrasonography and intra-vaginal dynamometry. Urine leakage volume was estimated based on incontinence pad weight gain. Separate linear regression models were used to evaluate the associations between variables representative of pelvic floor load exposure (posterior fornix sensor pressure [PFSP] and pelvic accelerations) and changes in pelvic morphometry, PFM function, and incontinence pad weight observed after the run.

After the run, the levator hiatus was larger and the bladder neck sat lower in the pelvis, but there were no significant differences in PFM active or passive forces measured using dynamometry. These changes were not different between those with and those without RI-SUI. Higher pelvic accelerations were associated with greater reductions in passive PFM stiffness after the run (R² = 20%-27%), but not with changes in pelvic morphometry. No associations were found between any measures of pelvic floor load exposure and changes in PFM force-generating capacity. Among runners with RI-SUI, greater pad weight gain occurred among those who ran with slower vector accelerations (R² = 0.27).

The magnitude of pelvic floor loading experienced during running does not appear to influence the transient loss in static pelvic organ support observed after running nor urine leakage volume.