Horizontal plane pelvic rotation minimizes hip ROM to keep the COM from dropping as far?

Horizontal plane pelvic rotation minimizes hip ROM to keep the COM from dropping as far?

• A. Rising too high
• B. Dropping as far
• C. Moving side-to-side
• D. Staying level

Answer: (B)

Horizontal plane pelvic rotation helps keep the center of mass from moving downward by reducing the amount of hip flexion/extension (hip ROM) needed during the step. When the pelvis rotates, the leg can swing and the trunk stays more upright, so gravity pulls the body vertical with less downward displacement of the center of mass. That means the center of mass is kept from dropping as far as it would without this pelvic motion, making that option the best fit. The other outcomes—rising higher, moving side-to-side, or staying level—do not describe the primary stabilizing effect of this pelvic rotation.

Horizontal plane pelvic rotation helps keep the center of mass from moving downward by reducing the amount of hip flexion/extension (hip ROM) needed during the step. When the pelvis rotates, the leg can swing and the trunk stays more upright, so gravity pulls the body vertical with less downward displacement of the center of mass. That means the center of mass is kept from dropping as far as it would without this pelvic motion, making that option the best fit. The other outcomes—rising higher, moving side-to-side, or staying level—do not describe the primary stabilizing effect of this pelvic rotation.