Answer: Although the
hip flexors are the prime movers in the
Captain's Chair Exercise (hanging leg lift), the abdominals are still contracting in this exercise. During this movement,
rectus abdominis contracts statically (without movement) and helps rotate and stabilizing the pelvis. In many cases the rectus abdominis is maximally contracted to stabilize the pelvis while you lift the legs toward the chest. This exercise is generally done with bent knees. Performing this exercise with straight legs creates a tremendous load on the lumbar spine and is only recommended for very fit athletes.