The goal of this study is to evaluate the effectiveness of using a regular menstrual tampon or a Uresta pessary to reduce urine leakage associated with running-induced stress urinary incontinence (RI-SUI) in females aged 18 and older. Secondly, the study aims to assess whether either intervention mitigates transient changes in pelvic morphology that occur following a single running bout. Lastly, we aim to evaluate whether participants continue using either intervention during running over the 4-week period following their in-lab participation. The hypotheses are: Hypothesis 1: Among females with RI-SUI, both a tampon and pessary used during a single running bout will reduce urinary leakage symptoms, with greater symptom reduction observed when using the pessary. Hypothesis 2: Participants will report high satisfaction and perceived symptom improvement with both the tampon and pessary, with higher satisfaction and greater improvement reported for the pessary. Hypothesis 3: Both the tampon and pessary will reduce pelvic floor strain incurred by the end of the run, as evidenced by less bladder neck descent, levator plate lengthening, and levator hiatus area increasing relative to that observed when no tampon or pessary is used. Hypothesis 4: A greater proportion of participants will report continued use of the pessary compared to the tampon over the 4-week post-lab period, with higher frequency of use and fewer reported discontinuations. We will perform within-subject comparisons against baseline values to determine the effect of each intervention on RI-SUI symptoms and pelvic organ support. Participants will complete a baseline questionnaire to collect demographic information and assess incontinence severity. They will then attend three laboratory visits within a 10-day period. At each visit, bladder volume will be standardized to between 100 and 200mL, then the participant will undergo three-dimensional (3D) transperineal ultrasound imaging conducted in a standing position. Following imaging, participants will complete a treadmill protocol consisting of 25-minutes running at a moderately difficult pace (rated at 13 - 14 on the Borg Perceiver Rate of Exertion scale), followed by 5 minutes of running at a higher intensity pace. During the run, participants will be asked at 5 minute intervals whether they experienced any urine leakage and to report their perceived amount of leakage. The ultrasound image protocol will be repeated immediately after the run. Participants will be allowed to keep the pessary and will be contacted 4-weeks after the final visit to evaluate whether or not they continued use of a tampon or the pessary, and, if so, we will ask them to report their satisfaction with the intervention(s) they used.