The Difference Between Sit-Ups and Crunches

If you’re a fan of core exercises, chances are both sit-ups and crunches are a staple of your workout routine. Or, you do one or the other, but consider them the same exercise with two different, interchangeable names. It may come as a surprise, but sit-ups and crunches are two completely different core exercises. Each works a different set of muscle groups, serves a different purpose, and has its own distinct range of motion. That said, each is worthy of being included in your workout routine, but you may want to lean toward one exercise over the other depending on your exact fitness goals.

Fitness experts help explain the key differences between sit-ups and crunches, how these exercises benefit the body and how to do each move correctly. Keep reading for tips on sit-ups vs. crunches, plus variations to make these exercises more beginner-friendly, pain-free, or challenging.

Sit-ups vs. crunches: What’s the difference?

Both sit-ups and crunches can activate and strengthen the abdominal muscles and begin in a similar position, but that’s where the similarities end. “Sit-ups and crunches primarily differ in their range of motion and the muscles they target,” says certified personal trainer Andrew White of Garage Gym Pro.

Sit-ups, White explains, are a full-body movement that involves lifting your entire torso from the floor up to your knees. This engages not only your abdominal muscles, but also your hip flexors and lower back (making it a great hip strengthening exercise as well). 

Crunches, meanwhile, are a “more isolated exercise,” White continues, that focus intensely on the rectus abdominis, more commonly known as the six-pack muscle, by lifting only your upper back off of the ground. Therefore, doing a sit-up requires a much larger range of motion and ultimately works more muscle groups than a crunch does.

Sit-ups vs. crunches: How they’re used

Certified personal trainer Jesse Zucker says sit-ups and crunches, while both popular ab workouts, serve different purposes. “Sit-ups are a full-body core exercise,” they explain. “They work different muscle groups and are great for advanced athletes to work their entire body, while strengthening all areas of their abs and hips.”

Crunches isolate the outermost layer of the abdominals, and Zucker says they’re a core exercise that is best for building up that area. “They’re also easier to perform than sit-ups,” they say. “Sit-ups risk injury because you need to stabilize your entire core to protect your spine as you move through the exercise.”

This, Zucker continues, can be difficult, especially as you try to keep your lumbar spine, or lower back, neutral when sitting up and down and hitting the floor. “Your lower back stays on the floor in crunches, so you don’t need to work as hard to protect it,” they say.

How to do a proper sit-up

1. Lie on your back with feet flat on the floor, legs bent, and knees pointed to the ceiling. Keep your feet hip-width apart. Place your hands behind your head with your elbows wide. Tuck your chin towards your chest.
2. Inhale, then exhale to draw your belly button towards your spine and brace your core. Maintain this deep core activation to keep your core muscles engaged and spine protected.
3. Push your feet into the ground and squeeze your glutes. Inhale, then exhale and sit all the way up until your chest reaches your thighs. Keep your abs engaged and your spine in a neutral position.
4. Inhale and slowly lower back down to the floor with control. Exhale to repeat for your desired number of reps.

To prevent injury during sit-ups, Zucker says to avoid pulling on your neck with your hands and to initiate the movement from your head and neck. “Keep your chin slightly tucked and your neck muscles engaged,” they say. “If you find yourself pulling on your neck, try crossing your arms over your chest.”

For more challenging sit-ups, you can try them on a medicine or stability bill.

As a general rule of thumb, White recommends starting with one to two sets of 10 or 15 repetitions for all core exercise. “However, fitness is not a one-size-fits-all journey,” he explains, “so adjust as needed for your comfort and fitness level.”

How to do a proper crunch

1. Lie on your back with feet flat on the floor, legs bent, and knees pointed to the ceiling. Keep your feet hip-width apart. Place your hands behind your head with your elbows wide. Tuck your chin towards your chest.
2. Inhale, then exhale to draw your belly button towards your spine and brace your core. Maintain this deep core activation to keep your core muscles engaged and spine protected.
3. On an exhale, lift only your shoulder blades and upper back up just a few inches off the ground, keeping your lower back in contact with the floor. Focus on contracting your abs to perform the lift, rather than using momentum or pulling with your arms.
4. Slowly lower them back down to finish one rep.

For a more challenging crunch, hold a free weight or medicine ball in your hands while doing the same movements. You can also “crunch” your obliques, or your waist muscles, by lying on your side and touching your left knee to your left elbow, or your right knee to your right elbow.

Benefits of sit-ups and crunches

Regardless of whether you do sit-ups vs. crunches or both, you can expect numerous health benefits. “They strengthen your core, which improves balance, stability, and overall body strength,” White says. “These exercises also enhance muscular endurance and contribute to better posture.”