Hip Flexion Angles During Supine Range of Motion and Bodyweight Squats

During the lowering phase of a squat, it has been observed that a posterior pelvic tilt (PPT) may occur when squatting to full depth. Research suggests that defaulting to compensatory movement strategies, such as PPT, during the squat may correlate with risk of lower extremity and trunk pathology. The purpose of this study was to examine hip flexion (HF) angles at the point when PPT occurs among three conditions: standard squats, heel raise squats, and supine passive HF; analyzing the differences in depth between standard and heel raise squats; and calculating differences in knee angles and ankle excursion between standard and heel raise squats. 28 participants performed bodyweight squats and underwent supine passive HF while outfitted with 32 retroreflective motion capture markers. Hip, knee, and ankle joint angles were extracted at the point of PPT. A one-way repeated measures ANOVA was used to determine differences in hip joint angles between conditions, and a paired sample t-test was used to compare knee angles, ankle excursion, and squat depth between standard and heel raise squats. HF angles at PPT remained unchanged across all conditions. However, significantly greater knee flexion, ankle excursion, and squat depth were observed in the heel raise squats compared to the standard squats. Results suggest that PPT is a compensatory movement that occurs as the femur compresses into the acetabulum once hip flexion has been exhausted.