Restriction in Pelvis and Trunk Motion in Postpartum Runners Compared With Pre-pregnancy

Background: Biomechanical changes in gait during pregnancy have been well studied in walking but not in running. Objective: To specifically examine adaptations in running biomechanics pre- to post-pregnancy, especially in the pelvis and trunk. Study Design: Pilot study. Methods: Five regular runners who were pregnant for the first time participated in this study. Participants ran at a self-selected speed on an instrumented treadmill while trunk, pelvis, and lower extremity kinematics were recorded. Baseline biomechanics were recorded prior to conception or within the first 14 weeks of gestation. Follow-up testing occurred at 6 weeks postpartum. Digital surveys were administered at baseline and 6 weeks postpartum, as well as at 14, 22, and 30 weeks of gestation. Surveys queried information regarding training characteristics, experience of pain, and perceived injury risk compared with pre-pregnancy. Results: Pelvis and trunk rotation excursions, sagittal hip range of motion, and cadence decreased from baseline to post-pregnancy, whereas stance time, step width, and sagittal knee range of motion increased. Average running volume and pace decreased postpartum, although variation occurred among participants. Abdominal pain was reported by 2 participants during pregnancy, with 2 participants reporting increased perceived injury risk. Conclusion: Taken together, these findings suggest postpartum runners restrict pelvis and trunk motion and increase gait stability, potentially as a protective response. Despite sample size, this pilot study presents initial evidence of biomechanical changes to running gait that occur pre- to post-pregnancy, which may have implications in developing support for pregnant and postpartum women interested in continuing or returning to running.