there are two ways to do a sit-up:

  • the easy way, which is the way you probably do it
  • and the hard way, which involves
    • maintaining posture of straight back, with shoulders in their proper position
    • as if you were standing confidently, unafraid, in front of an audience, perhaps as if you were finishing an opera, arms extended, embracing the world.

I've been doing them wrong my whole life.

I'm wondering what sort of difference I can expect in my abdomen. Which affects what muscles differently?

3 Answers 3


You shouldn't do sit-ups at all. Sit-up are mainly done by your hip flexors, but these are strong enough most of the time. Do really target your abs, you should do crunches. https://en.wikipedia.org/wiki/Crunch_(exercise).

Every time you flex your hip (angle between legs and hip), it's done by your hip flexors. Every time you flex your spine, it's done by your abs.

  • Not sure if I agree with you on that. For anyone else here's a rather beefy study analyzing position, foot support, and knee angle with EMG results following along. ir.library.oregonstate.edu/downloads/3484zk623
    – Eric
    Commented Feb 6, 2018 at 0:56
  • 1
    Spinal flexion is done by the upper and lower abs togheter, crunching the hip is done by the psoas muscle, quadricep and lower abdominals
    – Ekaen
    Commented Apr 8, 2018 at 9:41

To lessen the strain, I tend to do them laying at a 45° angle. I can keep my back straight and slowly sit up and lay back down using my abs without using momentum. My upper body weighs more than my lower half and I tend to use my legs more when they're held down or propped under something. I might have to do a few extra, but doing them in this position allows me to use my abs more with less arm and leg use when sitting up and less stress/pain on my back.


Fact is, neither of these sit ups realistically will build any muscle in your abdomen unless you are either relatively weak(doing under 20 sit ups), or if you are using a weight plate or kettlebell. However, they still are a form of exercise, so your gut might disappear if you do them consistently, but not because you are building muscles(most likely), but because you are burning a little, tiny bit of fat every time you do a sit up. Sit ups are harmful to your lower back though, anyway, if you want defined abs you should try doing pull ups, barbell squats, deadlifts(only once a week), push ups, and dumbbell/barbell rows. You also should also combine this with cardio and keep a fair diet.

  • 3
    Speaking as someone who has defined abs and who regularly performs all the above exercises, I can tell you this: none of those exercises will give you defined abs. Those exercises will build and strengthen your core (chinups is a close one for abs development); however, they won't make your abs defined; low body fat % and specific abs exercises are required if you do want your abs to pop. Spend some time here for more info. Commented Sep 5, 2015 at 22:58
  • @Kneel-Before-ZOD I said to keep a good diet with cardio, too, though. And I know for a fact that squats, pull ups, and deads certainly strengthen stomach muscles. Commented Sep 5, 2015 at 23:00
  • Strong stomach muscles are required for abs definition; however, for your abs to be really defined, you have to go beyond strong stomach muscles. All things being equal (i.e. considerable low fat %), you can easily tell between people performing abs exercises and those who don't. Don't take my word for it; read up on it, experiment with the exercises, and compare results. Commented Sep 5, 2015 at 23:12
  • @Kneel Before Zod That is true, but I think this user is searching for six pack abs, not the ones that are down to 3 or 4 percent body fat. Buy to get a six pack, diet is the main factor, I'd say. Commented Sep 6, 2015 at 1:43
  • eh all of these comments are off-topic, I'm not particularly in search of 6-pack-abs, I was more interested in the various fulcrums and pivot points in the musculoskeletal model of a hunched sit-up vs. straightened-back one
    – paIncrease
    Commented Sep 9, 2015 at 19:07

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