Past 90 degrees, all but the iliopsoas becomes actively insufficient (they go slack).
The rectus femoris, TFL, and all the adductors coordinate with the iliopsoas (which is really two muscles sharing common insertion points: the iliacus and the psoas) to flex the hip but only to 90 degrees. Which muscles perform that motion? There are 11 hip flexors, most of which assist in flexion including the adductors and abductors. Raising your leg is hip flexion, and hip flexors are what flex your hip, not abdominal muscles. Unfortunately for the majority of folks favoring this type of exercise, leg raises don’t actually work your abdominal muscles effectively, if at all. You’ll often see this move in the ab-day circuit along with Russian twists and side bends (also not ideal ab moves, btw), the perpetrator of the movement swinging legs all willy-nilly up and down.
If there is any move personal trainers have seen or even programmed quite frequently and largely in vain, is the hanging leg raise, or lying leg raise.
