Which adductor muscle has fibers that can concentrically accelerate extension of the femur?

The adductor muscle that can concentrically accelerate extension of the femur is the Adductor Magnus. This muscle contains both an anterior and a posterior portion, with the posterior fibers specifically playing a crucial role in hip extension. While the adductor muscles are primarily known for their action in hip adduction, the Adductor Magnus also contributes to movements such as extension and internal rotation of the hip, particularly during certain activities like running or transitioning from sitting to standing.

In contrast, the other adductor muscles—such as the Adductor Longus, Adductor Brevis, and Gracilis—are more focused on hip adduction and flexion without significant contribution to hip extension. Therefore, the unique anatomical structure and function of the Adductor Magnus distinguish it as the muscle responsible for accelerating the extension of the femur, making it the correct answer in this context.