28 - The association between pelvic floor loading experienced during running and changes in pelvic organ support observed after the run: an observational cohort study

Hypothesis / aims of study Among female runners, a single running bout results in a transient reduction in pelvic organ support [1] yet it is not clear if and how exposure of the pelvic floor to loading during running is implicated. Understanding this relationship might allow us to explore biomechanical interventions to alleviate running-induced urinary incontinence (RI-UI), which is experienced by up to 3 in 10 female runners [2] . We hypothesized that greater pelvic floor loading would be associated with greater reductions in pelvic organ support, pelvic floor muscle (PFM) stiffness and PFM strength measured after running. Study design, materials and methods This was an observational cohort study. Adult female runners with and without RI-SUI were recruited. Among other exclusion criteria, runners were excluded if they reported leakage associated with urinary urgency or reported inadequate running exposure. Among other tasks beyond the scope of this report, after performing three maximum effort vertical jumps for normalization purposes, runners completed a standardized 37-minute treadmill run with a pressure sensor placed in the posterior fornix of the vagina [3] to infer pelvic floor loading exposure and a triaxial accelerometer adhered to the skin overlying their pelvis to infer ground reaction forces. Peak posterior fornix sensor pressure (PFSP), peak PFSP normalized to vertical jump, and cumulative PFSP (evaluated as the area under the pressure-time curve) as well as peak vertical and vector accelerations were computed from data recorded during running at a self-selected pace (12-14 on the Borg Scale) for 30 minutes. Before and immediately after the run, in standing, pelvic morphometry was evaluated using transperineal ultrasound imaging and maximal PFM voluntary contraction force was evaluated using dynamometry, then in supine, peak passive PFM force (passive tone) was evaluated also using dynamometry. Separate linear regression models (α=0.05) evaluated the associations between both pelvic floor loading exposure and pelvic accelerations and changes in pelvic morphometry and PFM function induced by the run. Due to the exploratory nature of this study, alpha adjustments for multiple statistical comparisons were not performed. Results Nineteen female runners with and twenty runners without RI-SUI participated. As reported elsewhere [1] based on the same dataset, changes in pelvic morphometry but not pelvic floor muscle force outcomes were induced by the run, while no between-group differences were observed. The PFSP dataset was incomplete due to instrumentation issues and sensor dislodgement resulting in variable sample sizes among regression equations. Table 1 presents the amount of variance in the data explained by each model and the p-values associated with the overall models and the slope coefficients. Table 2 presents the model coefficients. Interpretation of results A more cranial bladder neck position before running predicted greater caudal displacement of the bladder neck after the run, independent of loading exposure, and explaining 34 to 35% of the variance in the data. No significant relationships were found between pelvic floor loading exposure (PFSP, pelvic acceleration) and changes in pelvic organ support nor changes in maximum PFM contraction force observed after the run. Higher pelvic accelerations, but not higher PFSPs, were associated with greater reductions in passive PFM stiffness (tone) after the run, explaining 20–27% of the variance in the data. This finding may be spurious, as several statistical models were tested. Concluding message The magnitude of pelvic floor loading forces experienced during running does not appear to influence the transient loss in static pelvic organ support observed after running, but may have a small impact on passive stiffness of the PFMs. Download: Download high-res image (185KB) Download: Download full-size image Figure 1 . TABLE 1: Explained variance and parameter significance for regression models between pelvic floor loading exposure and pelvic morphometry/pelvic floor muscle outcomes. Download: Download high-res image (181KB) Download: Download full-size image Figure 2 . TABLE 2. Regression equations between pelvic floor loading exposure and pelvic morphometry/pelvic floor muscle outcomes. Equations take the form B0+B1x+B2y, where B0 is the intercept and B1, B2 are slope coefficients. Funding Physiotherapy Foundation of Canada Clinical Trial No Subjects Human Ethics Committee University of Ottawa Health Sciences and Sciences Research Ethics Board Helsinki Yes Informed Consent Yes

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