In midstance, the quadriceps perform which type of muscle action to extend the knee?

In midstance, the quadriceps perform which type of muscle action to extend the knee?

• A. Isometric
• B. Concentric
• C. Eccentric
• D. Isokinetic

Answer: (B)

In midstance, the leg bears the body's weight and the knee moves toward extension. Extending the knee requires the quadriceps to shorten as they contract, which is a concentric muscle action. This concentric shortening straightens the knee and helps stabilize the limb as you progress over the stance leg. The other options don’t fit this phase: eccentric contraction would lengthen the muscle to control knee flexion (seen earlier in stance), isometric would hold the knee angle without changing length, and isokinetic describes a speed-controlled movement typically not relevant to natural gait. So the quadriceps act concentrically to extend the knee in midstance.

In midstance, the leg bears the body's weight and the knee moves toward extension. Extending the knee requires the quadriceps to shorten as they contract, which is a concentric muscle action. This concentric shortening straightens the knee and helps stabilize the limb as you progress over the stance leg. The other options don’t fit this phase: eccentric contraction would lengthen the muscle to control knee flexion (seen earlier in stance), isometric would hold the knee angle without changing length, and isokinetic describes a speed-controlled movement typically not relevant to natural gait. So the quadriceps act concentrically to extend the knee in midstance.