# Alterations in pelvic kinematics with speed, incline, and fatigue in female runners

## TL;DR

This study examines how speed, incline, and fatigue affect pelvic movement in female runners, finding that these factors significantly alter motion patterns, potentially increasing injury risk.

## Contribution

The study provides novel insights into sex-specific pelvic kinematic responses to speed, incline, and fatigue in female runners.

## Key findings

- Higher running speeds increase peak pelvic rotation, tilt, and obliquity, as well as their ranges of motion.
- A 10% incline increases peak pelvic obliquity and rotation and expands motion ranges, unlike a 5% incline.
- Fatigue increases peak pelvic rotation and motion ranges for rotation and tilt, with altered incline effects under fatigue.

## Abstract

In running, female runners show higher overuse-injury rates, partly due to sex-specific anatomy and biomechanics. Pelvic motion is central to lower-limb kinematics, however, female-specific responses are underexamined. This study tested how running speed, incline, and fatigue influence pelvic rotation, tilt, and obliquity in recreational female runners.

Twenty-two females completed treadmill trials at 10, 12, and 14 km/h on level ground and at 10 km/h with 5% and 10% inclines, before and after a 30-minute run at 80% heart-rate reserve to induce moderate fatigue. A 3D motion-capture system recorded pelvic rotation, tilt, and obliquity at heel-strike, toe-off, peak values, and ranges of motion. Linear mixed-effects models assessed main and interaction effects; asymmetry was quantified via symmetry index between left and right gait cycles.

Higher speeds increased peak pelvic rotation, tilt, and obliquity, and enlarged rotation and obliquity range of motion. A 10% incline raised peak pelvic obliquity and rotation and increased range of motion for rotation, tilt, and obliquity; a 5% incline had no measurable effect. Fatigue increased peak pelvic rotation and range of motion for rotation and tilt. A fatigue × 10% incline interaction showed that incline-related increases in tilt range of motion observed when fresh were reduced under fatigue. Pelvic tilt asymmetry rose with speed.

Speed, incline, and fatigue each modulate pelvic kinematics in recreational female runners, with effect sizes often exceeding reports from mixed-sex samples. Notably, greater frontal-plane motion at higher speeds and increased transverse-plane motion with incline and fatigue may heighten loads on the iliotibial band, hamstrings, or lumbar spine.