When I look up how to do hanging knee raises, almost all fitness sources say "lift your knees past 90 degrees to your chest", while a few rare ones say "use your abs to lift your knees". It seems when I do these, there are two ways to do this, both where I keep a neutral back and tense my abs, and start with legs slightly above parallel to my body below me.

  1. Literally lift my legs using my hip flexor muscles. My core gets activated as my legs get higher to stabilize, and I would assume as knees go past 90, my lower abs contract. This feels like doing a leg/knee raise off a bench, with the hard part being the lowering aspect.

  2. Literally use my core to "crunch" my knees up to my stomach, ending with a slight pelvic tilt. This feels like I'm not using hip flexors hardly at all, and I feel much more ab muscle activation. I slowly lower down. This feels similar to a reverse crunch on a bench.

My question is, which one is correct? Or are they both correct? They both look the same if I were to observe someone doing these, but the muscle activations feel incredibly different.

  • Which one is "correct" depends on your goal. Are you doing this movement to train your trunk or your hip flexors or something else?
    – Thomas Markov
    Jan 21, 2022 at 19:17
  • I am focusing on core
    – user32213
    Jan 21, 2022 at 20:57
  • Think about which joints are moving in this exercise and what muscles cross those joints. You have to conclude that this is almost completely an exercise for hip flexors no matter how you do it. However, you might brings your knees to 90 degrees and fix them there, and then add on to this a small tuck of the pelvis, while you maintain the 90 degree knees. I'm not recommending this, but it might be a way to take the hip flexors out of the exercise.
    – Chris
    Jan 23, 2022 at 19:16

1 Answer 1


You may feel different activations because of one of the two muscles being weaker in comparison to the other. Think of it as when you first did push ups, you felt more activation of your delts than you chest because we use at least some of out chest in day to day work but not our deltoids so much in comparison. Same thing with the hip flexors and the core.

So, you could keep doing them neutrally (with no preference of the muscle group used) and the weaker one will catch up OR focus on you core more as it is your primary goal.

This is assuming that you are having a good form.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.