Which muscle is especially associated with controlling hip flexion/jackknifing during loading response?

Which muscle is especially associated with controlling hip flexion/jackknifing during loading response?

• A. Iliopsoas
• B. Gastrocnemius
• C. Tibialis anterior
• D. Gluteus maximus

Answer: (D)

Controlling hip flexion during loading response relies on eccentric hip extensor action to keep the pelvis and trunk from collapsing forward as the body weight shifts onto the stance leg. The gluteus maximus is the primary hip extensor active in this phase, slowing hip flexion and stabilizing the pelvis to prevent jackknifing. It works to keep the thigh from collapsing forward while the foot accepts load. The iliopsoas would promote hip flexion, which could contribute to forward tipping, so it isn’t the main controller here. The gastrocnemius and tibialis anterior mainly influence ankle and knee movements rather than the hip, so they don’t provide the primary control of hip flexion at this moment.

Controlling hip flexion during loading response relies on eccentric hip extensor action to keep the pelvis and trunk from collapsing forward as the body weight shifts onto the stance leg. The gluteus maximus is the primary hip extensor active in this phase, slowing hip flexion and stabilizing the pelvis to prevent jackknifing. It works to keep the thigh from collapsing forward while the foot accepts load. The iliopsoas would promote hip flexion, which could contribute to forward tipping, so it isn’t the main controller here. The gastrocnemius and tibialis anterior mainly influence ankle and knee movements rather than the hip, so they don’t provide the primary control of hip flexion at this moment.