What would be an appropriate exercise for strengthening hip flexion?

Strengthening hip flexion involves focusing on the muscles that bring the thigh towards the torso, primarily the iliopsoas and rectus femoris. The option involving the stability ball while tilting the pelvis from a supine position effectively targets these muscles. In this exercise, as you tilt the pelvis, you engage the hip flexors to lift the legs and bend the knees, which directly works on hip flexion.

The leg press focuses more on knee extension and overall leg strength rather than isolating hip flexion. Standing calf raises target the calf muscles, which are not involved in hip flexion. Seated leg curls concentrate primarily on the hamstring muscles and knee flexion. Thus, the choice of tilting the pelvis with the stability ball directly engages the hip flexors, making it the right option for strengthening hip flexion.