During midstance, the quadriceps act concentrically to do what? (rephrase)

During midstance, the quadriceps act concentrically to do what? (rephrase)

• A. Flex the knee and unload the limb
• B. Dorsiflex the ankle
• C. Pronate the foot
• D. Extend the knee and support body weight

Answer: (D)

In midstance the leg is supporting the body's weight while the knee is kept near full extension. The quadriceps contract concentrically to extend the knee and stabilize the joint, producing the knee extension moment needed to resist the forward collapse and to keep the leg upright as weight is borne. This action directly supports body weight and maintains a straight knee for a smooth, stable stance. Dorsiflexion involves the ankle, not the knee, so that action is not performed by the quadriceps. Pronation is a movement of the foot, again not driven by the quadriceps. Flexing the knee would oppose the extended posture needed to support weight in midstance, so it wouldn’t describe the role of the quadriceps here.

In midstance the leg is supporting the body's weight while the knee is kept near full extension. The quadriceps contract concentrically to extend the knee and stabilize the joint, producing the knee extension moment needed to resist the forward collapse and to keep the leg upright as weight is borne. This action directly supports body weight and maintains a straight knee for a smooth, stable stance.

Dorsiflexion involves the ankle, not the knee, so that action is not performed by the quadriceps. Pronation is a movement of the foot, again not driven by the quadriceps. Flexing the knee would oppose the extended posture needed to support weight in midstance, so it wouldn’t describe the role of the quadriceps here.