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The Difference Between Sit Ups and Crunches

Updated on April 21, 2010

Even though nowadays the crunch and sit-up are different exercises, the sit-up is the original.  Over time, and with research, the crunch evolved from the sit-up.  Let's start with the original.  To perform a sit-up, you start by laying on your back and placing your feet flat on the ground with your knees bent.  Then, you lift your head and shoulders, middle back, and low back off the ground coming to a seated position where you are mostly balanced on your tailbone.  It's common, but unnecessary, to have someone hold your feet down while doing sit-ups.  Ideally, you're strong enough that you don't need a buddy.  In fact, if you've taken a Pilates class, you may have done the Pilates version of a sit-up, called the roll-up.  There's nobody there to hold your feet - it's all about using your core!

Now on to the crunch.  The crunch starts the same way by laying on your back, feet grounded, knees bent.  The difference is the amount of movement.  During the crunch, you lift your head and shoulder blades off the ground, then lower.  Your mid and lower back stays on the floor the entire time.  Your hands can be placed behind your head or crossed over your chest.

Both the sit-up and the crunch work your abdominals; specifically, the muscle - that when well-trained - gives you a 6-pack.  However, the sit-up also works the muscles that flex your hip joint.  The sit-up works your abs until you lift your lower back off the floor.  Once your back leaves the ground, you are using your hip flexors to finish the exercise.  There's nothing wrong with's just something to be aware of.

So, if you want to work out your abs, the crunch is a very effective exercise.  If you want to train your abs and hip flexors, the sit-up is great.  Either way, your abs will thank you!

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    • mixfitness profile image

      mixfitness 7 years ago from Round Hill, VA

      WPoynter -- I can't say which one would strengthen your abs faster. It all depends on where you're starting from. A safe progression would be to start with the crunches to build your abdominal strength. Graduate to sit-ups as long as you don't have any lower back concerns. Trying to force results leads to injury and burn out.

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      WPoynter 7 years ago

      Would the crunches strengthen my abs faster though? If not surley sit ups are the way to go?

    • mixfitness profile image

      mixfitness 7 years ago from Round Hill, VA

      Thank you, GmaGoldie!

    • GmaGoldie profile image

      Kelly Kline Burnett 7 years ago from Madison, Wisconsin

      So few people understand this! 5 stars! I will be sure to link back to you. Wonderful job! In the water, since the back is not supported, all too often the back muscles are engaged - bending the knees in combination of hunching ensures the targeted muscles are contracted.

      Great post! Keep up the great work!

    • mixfitness profile image

      mixfitness 7 years ago from Round Hill, VA

      Quildon -- I don't think you got it wrong. It sounds like what you saw was still a crunch. There are a plethera of ways to increase the intensity of a crunch, including adding leg movement. Think of the sit-up as what you see the military doing. If you're interested in reading more about the abs (including my thoughts on the upper and lower abs) visit my profile and click on the link to my blog:) Thanks for commenting!

    • quildon profile image

      Angela Joseph 7 years ago from Florida

      I guess I got it wrong. I saw exercises on TV where they combined sit-ups with leg raises with the knees bent and they called that the crunch. I've tried it and it is a more intense ab workout than just sit-ups alone. It works both the upper and lower abs.

    • mixfitness profile image

      mixfitness 7 years ago from Round Hill, VA

      Angela_Michelle: Both the sit-up and the crunch work the abs the exact same way because they begin the same way. With the sit-up, your hip flexors will be exercised in addition to your abs. Hope that makes sense! Thanks for leaving a comment:)

    • angela_michelle profile image

      Angela Michelle Schultz 7 years ago from United States

      So how are they different on how they work the abs? I guess more specifically, what kind of effect will you get from each one?