Which muscle acts as an antagonist to the gluteus maximus?

The gluteus maximus is a powerful muscle located in the buttocks, primarily responsible for hip extension, outward rotation, and abduction of the hip. An antagonist is a muscle that opposes the action of another muscle—in this case, the gluteus maximus.

The iliacus, along with the psoas (forming the iliopsoas), is responsible for hip flexion. This action counteracts the extension that the gluteus maximus provides. When the gluteus maximus contracts to extend the hip, the iliacus would need to relax or oppose that action to allow for hip flexion, thus acting as an antagonist.

The other choices, while having their own roles in movement, do not primarily act as antagonists to the gluteus maximus. The rectus femoris also assists with hip flexion but does not oppose the gluteus maximus efficiently in terms of its specific roles in movements of the hip. The psoas muscle certainly contributes to hip flexion, but since the iliacus is a more direct counterpart in this functionality when considering the overall dynamics of hip actions, it is the muscle that best exemplifies the antagonistic relationship. The rectus abdominis, while important