APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -Performance of hip extension and knee flexion exercises increases when the hamstring muscles are in a lengthened condition. The hamstring muscles (particularly the semitendinosus) are more involved in knee flexion than in hip extension.

Detailed explanation-2: -The primary function of the hamstrings at the hip is to extend the hip, whereas at the knee it is to flex it. These functions are essentially the opposite of the quadriceps, making the hamstrings an antagonist muscle to the quadriceps in most single joint motions.

Detailed explanation-3: -As these are bi-articular muscles, knee extension occurs by bringing the origin and insertion of the hamstring together, by reducing the flexion angle of the hip joint with retroversion of the pelvis when the knee is extended in the sitting position.