Yeah I have the same problem man. An ab machine will definitely activate your hip flexors. An ab wheel will have less because you’re not pulling your knees to your chest. Just be careful on the way down it’s easy to much too much stress doing that. Remember the activation with the ab wheel comes when you’re pulling the wheel back. Make sure you’re using your core to pull yourself back up.

I’d suggest doing ab excercises that eliminate your legs. Planks, those sit-ups I showed you, even laying on the ground and picking up a medicine ball from behind your head will be better options than the ab machine.

You want to crunch around the top of your stomach, not your waist if that makes sense.