The acute effects of running on pelvic floor morphology and function in runners with and without running-induced stress urinary incontinence

Introduction and hypothesis: The aim of this study was to examine the impact of a single running session on pelvic floor morphology and function in female runners, and to compare those with and without running-induced stress urinary incontinence (RI-SUI).

Methods: This cross-sectional, observational study involved two groups: female runners who regularly experienced RI-SUI (n = 19) and runners who did not (n = 20). Pelvic floor muscle (PFM) properties were assessed using intravaginal dynamometry during maximal voluntary contractions (MVC) and during passive tissue elongation. The morphology of the pelvic floor was assessed at rest, during MVC and during maximal Valsalva maneuver (MVM) using 2D and 3D transperineal ultrasound imaging before and after a running protocol. Mixed-effects ANOVA models were used to compare all outcomes between groups and within-groups, including the interaction between group and time. Effect sizes were calculated.

Results: No changes in PFM function assessed using intravaginal dynamometry were observed in either group after the run. Significant and large within-group differences were observed on ultrasound imaging. Specifically, the area and antero-posterior diameter of the levator hiatus were larger after the run, the bladder neck height was lower after the run, and the levator plate length was longer after the run (p ≤ 0.05). At the peak MVM and MVC, the bladder neck height was lower after the run than before the run (p ≤ 0.05). No between-group differences were observed for any outcomes.

Conclusions: Running appears to cause transient strain of the passive tissues of the female pelvic floor in runners both with and without RI-SUI, whereas no concurrent changes are observed in PFM contractile function.