Exercise Tips: Sit-ups vs. Crunches

4 min. read — March 24, 2022

If you’re focused on building your physique or even just staying in shape, you’re going to need to know some key core exercises, including sit-ups and crunches. Although you may think you’re well-versed in athletics and physical conditioning, unless you’re a dedicated athlete or trainer, you probably aren’t as aware of the differences between sit-ups and crunches as you think you are. You even might get confused! Sit-ups and crunches are rather similar, but unfortunately, a lack of knowledge about the differences between these two exercises and their respective proper forms can lead people to perform them incorrectly. This improper form can cause damage to your muscles, especially those in your back.

So, what are the differences between sit-ups and crunches, and what are the consequences of performing them improperly? To begin, a proper sit-up lifts the upper body into an upright sitting position, exercising more muscles, whereas a proper crunch only lifts the shoulders and upper back, only exercising the abdominal muscles. Both of these exercises have a couple of variations, but it is important to perform each one at a slow, steady pace and to breathe correctly as you perform them.

A sit-up exercises a variety of muscles, most importantly your hip flexors, your chest muscles, your lower-back muscles, and your abdominal muscles. A sit-up strengthens all of these muscles because they are all required to lift the torso into the aforementioned upright sitting position. In contrast, crunches only target the abdominal muscles, which are rectus abdominis and the obliques. Additionally, crunches (also known as curl-ups) are much less likely to cause back problems than sit-ups. Because of a sit-up’s wider range of motion, it causes the spine to press against the surface on which the sit-up is being performed. This is one reason why some people prefer to do sit-ups on mats or other soft surfaces. However, the risk of injury from sit-ups depends mostly on one’s spinal column and history of back problems. Those with thicker, heavier spinal columns experience injury from sit-ups sooner and more easily than those with thinner, more lightweight spinal columns.

The best way to prevent injury while exercising is to correct one’s form and perform each exercise properly. The starting position for a sit-up or a crunch is the same: you should lie flat on your back with your legs bent at a 90 degree angle and your feet one shoulder-width apart. Your feet should be flat on the ground and can be held in place by an object or by a partner. You should either fold your arms across your chest, place them at your sides on the ground with your palms facing down, or place your hands behind your head with your elbows bent and out to the sides. Alternatively, sit-ups can be performed with your legs straight on the ground. To perform a sit-up, lift your torso away from the ground until you are sitting upright with your chest close to your legs (or, if your legs are straight on the ground, until your torso is perpendicular to your legs). This will mainly work your abdominal muscles. After this, you should slowly lower your upper body until you are back in your starting position. To perform a crunch, you should only lift your head, shoulders, and upper back off of the floor as if you were performing half of a sit-up. Once your shoulders are at a 30 degree angle to the ground, stop and then slowly lower your body back down to your starting position. Be careful not to put too much strain on your neck in either exercise and to exhale as you lift yourself up and inhale as you lower yourself down.

In summary, sit-ups and crunches differ in their form, target muscles, and risks. Sit-ups exercise more muscles than crunches and lift the entire torso off of the ground, offering greater risk for injury, whereas crunches solely work the abdominal muscles and only lift the upper back. When properly executed, these exercises can have noticeable effects over time. Even when performed sparingly, they help to build stronger, healthier bodies for those who take the time to perform them.