AFAA Personal Trainer Certification Practice Exam 2025 - Free Personal Trainer Practice Questions and Study Guide

The iliopsoas is the primary muscle group responsible for hip flexion, which is the movement that brings the knee closer to the chest or the thigh closer to the torso. This muscle group consists of two main muscles: the psoas major and the iliacus.

When the hip is flexed, these muscles shorten and contract, enabling activities such as walking, running, and kicking. The iliopsoas is often referred to as one of the most important hip flexors due to its significant leverage and ability to produce powerful movements at the hip joint.

While the quadriceps play a role in hip movement, they are primarily knee extensors, and their contribution to hip flexion is much less significant. The hamstrings are primarily responsible for hip extension and knee flexion, while the gluteal muscles primarily assist with hip extension, abduction, and external rotation rather than flexion. Thus, the iliopsoas stands out as the correct answer in identifying the primary muscles responsible for hip flexion.