During midstance, quadriceps act concentrically to do what?

During midstance, quadriceps act concentrically to do what?

• A. Flex the hip
• B. Extend the knee
• C. Dorsiflex the ankle
• D. Extend the toes

Answer: (B)

During midstance the leg is supporting the body's weight and the knee must stay straight to allow smooth forward progression. The quadriceps are knee extensors, so their concentric contraction serves to extend and stabilize the knee against the flexion forces caused by body weight. This keeps the knee in extension and provides a solid pillar for transferring weight toward the stance leg as you move forward. Other actions listed aren’t performed by the quadriceps: hip flexion is driven by hip flexors, not knee extensors; dorsiflexion is done by ankle dorsiflexors; extending the toes involves toe extensors.

During midstance the leg is supporting the body's weight and the knee must stay straight to allow smooth forward progression. The quadriceps are knee extensors, so their concentric contraction serves to extend and stabilize the knee against the flexion forces caused by body weight. This keeps the knee in extension and provides a solid pillar for transferring weight toward the stance leg as you move forward.

Other actions listed aren’t performed by the quadriceps: hip flexion is driven by hip flexors, not knee extensors; dorsiflexion is done by ankle dorsiflexors; extending the toes involves toe extensors.