Sex difference in hip adduction during the stance phase of running: A swing phase problem?

Purpose: The purpose of the current study was to: 1) evaluate sex differences in peak hip adduction during the late swing and stance phases of running and 2) determine if peak hip adduction during late swing is predictive of peak hip adduction during stance. Methods: 15 female and 16 male heel strike runners ran over ground at a speed of 4 m/s. Hip joint kinematics during running were quantified using a 3D motion capture system. Sex differences in peak hip adduction during the late swing and stance phases were compared using independent sample t-tests. Linear regression analysis was used to determine the relationship between late swing and stance phase hip adduction. Results: Compared to males, females exhibited significantly greater peak hip adduction during both the late swing (mean and standard deviation: 8.5 and 2.6 vs 6.1 and 2.8 degrees, p = 0.019) and stance phases of running (mean and standard deviation: 13.3 and 4.2 vs 9.6 and 3.4 degrees, p = 0.011). Furthermore, late swing peak hip adduction was predictive of subsequent stance phase peak hip adduction (r = 0.63, p < 0.001). Conclusion: Sex differences in hip adduction during stance are influenced in part by late swing phase hip adduction. Further studies are needed to identify potential causes of excessive hip adduction during the late swing phase of running.