Inefficient impact absorption and reduced shock attenuation in female runners with stress urinary incontinence

Running has been associated with stress urinary incontinence (SUI) in female runners, with prevalence reaching 44 %. Surprisingly, many of these runners exhibit pelvic floor muscle strength and endurance that is similar or even greater compared to continent runners. Therefore, this study aimed to investigate other potential mechanisms associated with SUI in female runners, focusing on impact absorption and muscle function. Thirty-two female runners were divided into two groups: runners with and without SUI. Pelvic floor muscle function was assessed using the Peritron®, whereas the maximum isometric strength of the trunk and lower limb muscles was measured using a portable handheld dynamometer. Kinetic data, including vertical ground reaction force (GRF), energy absorption at the ankle, knee, and hip joints, and shock attenuation between the tibia and femur, were collected using a 3-D motion analysis system on an instrumented treadmill during running. Group comparisons were performed using the Student t-test and Mann-Whitney at a 0.05 significance level. There were no differences in pelvic floor, trunk and lower limb muscle function between groups. Despite similar vertical GRF, runners with SUI exhibited lower energy absorption at the ankle (p = 0.019; d = 0.54), higher energy absorption at the hip (p < 0.001; d = 0.85) and reduced shock attenuation between the tibia and femur (p = 0.038; d = 0.80) during running compared to continent runners. Runners with SUI differed in energy absorption and shock attenuation patterns, particularly at the hip and ankle. These findings suggest that incontinent runners exhibit inefficient energy absorption throughout the kinetic chain experiencing greater pelvic demands.