Both crunches and sit ups are easy exercises you can do anywhere, anytime.  Whether you’re at the gym or in the comfort of your own home, very little space is required to strengthen your abdominal muscles.  While people often refer to crunches and sit ups interchangeably, they are different exercises.

Yes, they appear similar, but don’t let that fool you.  There are physical differences in these workouts that set them apart from one another.  For example, sit ups are a bit more intense than crunches, as they target additional muscle groups outside of your core.

Crunches

Although they are both common abdominal exercises, there are key differences between crunches and sit ups.  A crunch is pretty much a “half sit up” as it only targets your abdominal muscles.  The lower half of your body typically remains on the floor for the duration of the exercise, unlike a sit up.  While performing a crunch, you are isolating your abdominal muscles.  While this is great for building a six pack, keep in mind crunches are not a holistic core training exercise, and are not designed to burn fat.

How to do a Crunch

1. To begin the crunch, lie completely flat on your back with your legs bent at your knees and your feet planted firmly on the ground, about a shoulder width apart.  You may place your hands behind your ears or cross them atop your chest.
2. Raise your head and shoulders from the floor and feel as your abdominal muscles contract.  Try to avoid pulling your head forward, as it may strain your neck.
3. Lower your head and shoulders back towards your starting position. Remember to exhale as you raise your head and shoulders then inhale as you lower them.

Sit ups

While crunches exclusively workout your abdominal muscles, a sit up is a slightly more intense exercise that strengthens your hip flexors, abdominal muscles, chest, neck, lower-back, as well as the muscles in your lower-legs.

While a stronger core can improve your posture and reduce your risk of back injuries, if not performed properly, sit ups can cause serious back injuries.  In fact, last July the US Army announced they are phasing out the two minute sit up test by late 2020.  For this reason, it’s imperative that you perfect your form and start slow with fewer repetitions.

How to do a Sit up

1. To begin the sit up, lie flat on your back with your legs bent at the knees. Optionally, you may hook your feet to an object for additional security, however this will put more focus on the muscles in the lower half of your body rather than your abdomen.
2. Place your hands behind your head, crossed atop your chest, or lying on either side of your body. For less involvement of your back muscles, slightly flex your neck so that your head is tucked forward.
3. Use your abdominal strength in order to curl your upper body forward until it is no longer on the floor and you are seated upright.
4. Lower to the floor, back towards your starting position. Remember to exhale as you raise your body and inhale as your lower back towards the floor.

What’s the Difference?

Both crunches and sit ups are common abdominal exercises for developing core strength.  However, while crunches isolate the muscles in your abdomen, sit ups target multiple muscle groups including the hip flexors and muscles in your lower-legs.

While proper form is essential when performing any exercise, it is especially important for sit ups.  Doing too many, soo soon, or doing sit ups incorrectly may lead to a lower back condition called hyperlordosis.  For this reason, follow the guides above, start slow and focus on proper sit up form to get the best, safest results.

It’s also important to note that neither sit ups nor crunches burn fat.  The only way to attain a flat and muscular stomach is to combine these exercises with a healthy, low-calorie diet and regular fat-burning aerobic exercise.

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