ACSM Personal Trainer Certification Practice Exam

What is the primary joint action of the iliopsoas muscle?

1. Extension

2. Flexion

3. Adduction

4. Abduction

The correct answer is: Flexion

The iliopsoas muscle, which is comprised of the iliacus and psoas major muscles, is primarily responsible for hip flexion. This muscle group plays a crucial role in lifting the thigh towards the torso, which is an essential movement in various activities such as walking, running, and climbing. When the iliopsoas contracts, it pulls the femur (thigh bone) towards the pelvis, resulting in flexion at the hip joint. This action is fundamental to many functional movements, including bending forward and bringing the knee up, making the iliopsoas a key muscle for mobility and stability around the hip. In contrast, the other joint actions mentioned—extension, adduction, and abduction—are primarily managed by other muscle groups. Hip extension, for instance, involves muscles such as the gluteus maximus, while adduction is typically achieved through the adductor muscle group. Abduction is primarily driven by the gluteus medius and minimus. Thus, the iliopsoas's specific role in flexing the hip joint firmly establishes its primary joint action as flexion.