Frontal plane pelvic rotation reduces upward COM displacement through what movement of the pelvis?

Frontal plane pelvic rotation reduces upward COM displacement through what movement of the pelvis?

• A. Pelvic drop on the stance side
• B. Pelvic retraction only
• C. Contralateral pelvic drop during stance
• D. Horizontal protraction only

Answer: (C)

In gait, moving the pelvis in the frontal plane (pelvic obliquity) can lower the peak height of the center of mass by tilting the pelvis so that the opposite side drops when the stance leg bears weight. This contralateral pelvic drop during stance helps keep the trunk and body closer to a level line, reducing how far the center of mass has to rise during part of the step. The effect is produced by the stance-side hip abductors controlling the pelvis and preventing excessive tilt, so a normal, well-controlled drop of the swing-side pelvis during stance contributes to a smoother, more energy-efficient motion. Pelvic drop on the stance side would tilt toward the stance leg and doesn’t specifically achieve the same reduction in vertical COM displacement. Pelvic retraction or horizontal protraction are movements in other planes and don’t address the frontal-plane adjustment that modulates vertical COM excursion.

In gait, moving the pelvis in the frontal plane (pelvic obliquity) can lower the peak height of the center of mass by tilting the pelvis so that the opposite side drops when the stance leg bears weight. This contralateral pelvic drop during stance helps keep the trunk and body closer to a level line, reducing how far the center of mass has to rise during part of the step. The effect is produced by the stance-side hip abductors controlling the pelvis and preventing excessive tilt, so a normal, well-controlled drop of the swing-side pelvis during stance contributes to a smoother, more energy-efficient motion.

Pelvic drop on the stance side would tilt toward the stance leg and doesn’t specifically achieve the same reduction in vertical COM displacement. Pelvic retraction or horizontal protraction are movements in other planes and don’t address the frontal-plane adjustment that modulates vertical COM excursion.