Hypothesis / aims of study
Pelvic floor strain during running has been observed in females both with and without running-induced urinary incontinence (RI-UI) (1). Since the posterior urethrovesical angle (PUVA) is linked to the functional integrity of proximal urethral support and larger PUVAs have been observed in females with SUI, we assessed whether PUVA before running, or PUVA changes after a bout of treadmill running differ between runners with and without RI-UI. Compared to continent runners, we hypothesized that incontinent runners would demonstrate larger PUVAs before and larger increases after a single bout of treadmill running.
Study design, materials and methods
This research ethics board-approved case-control study recruited female runners, ≥18 years old, with and without RI-UI, who had been running ≥10 km/week at ≥ 6 km/h for at least one year. Continent runners had never experienced urine leakage while running. Incontinent runners self-reported ≥ 1 episode of RI-UI/week or in at least half of their running sessions. Runners in both groups had to report rarely experiencing UI outside of exercise (≤once a month). Urgency-related leakage was also an exclusion criterion in both groups, but occasional urgency without leakage was not. Additional exclusion criteria were major urogenital surgery, pelvic organ prolapse > POP-Q stage 2, pregnancy or ≤1year postpartum, self-reported symptoms of energy deficiency or any injury or health condition that impacted treadmill running. The data collection session was scheduled within the first 15 days of the menstrual cycle if participants menstruated or at any convenient time if they did not. Data collection included transabdominal 3D ultrasound imaging (GE Voluson S6 system, RAB6-9 curvilinear probe; GE Healthcare, Toronto, Canada) to measure bladder volume (BV) in supine and transperineal measurement of the PUVA in standing. Images were acquired before and after a 38-minute treadmill run which consisted of a 6-minute warm-up, a 30-minute self-paced run (12-14 on the Borg rating of perceived exertion scale), and a 2-minute cool-down. 4D View (GE Healthcare) and ImageJ (National institutes of Health, USA) software were used to measure BV and PUVA, respectively, the latter defined as the angle between the posterior urethral wall and the bladder base (Figure 1), measured with the researcher blinded to participant’s symptoms. A repeated-measures general linear model was used to determine the impact of time (pre/post-run) and group (continent vs. incontinent) on PUVA, including BV and PUVA before the run as covariates.
Results
90 runners participated, PUVA visualization was poor in 13 participants thus they were excluded from the analysis. The incontinent runners (n=23) were older and had higher parity than the continent runners (n=54) (Table 1). Before the run, PUVA was not different between the groups (Table 1). PUVA increased after running in all participants (F (1,1)=0.16, p=0.03), with no significant effect of group (F(1,1=0.36, p=0.54), BV (F(1,1)=1.51, p = 0.22) nor interaction between group x time (F(1,1)=0.16, p=0.68).
Interpretation of results
Proximal urethral support is reduced in females after a treadmill run, as PUVA increased after running across the entire sample. Because there were no group differences and the effect sizes were small, it is unlikely that the PUVA alone contributes to RI-UI. This is in contrast to findings of larger PUVAs among those with SUI during activities of daily living (2) and may suggest that the pathogenesis of RI-UI is different from that of general SUI.