You’re not the only one who doesn’t know the difference between sit-ups and crunches. Both of them make your core stronger, but it can be hard to understand how they are different and what each one is good for.
“The main difference between the two is that in a crunch, the lower back never leaves the floor, unlike in a sit-up,” says Katharine Glazer, CPT. A crunch is a more focused and isolated exercise that only works your rectus abdominis, which are mostly your upper abs.
A sit-up, on the other hand, works more than one muscle group at once and has a wider range of motion. It works the rectus abdominis, hip flexors, transverse abdominis (deep core muscles), obliques (side abs), and lower back muscles. You’re using more muscles when you lift your torso all the way off the ground.
The debate over sit-ups and great crunches is much bigger than that. Experts say that you should keep reading to learn about the pros and cons of both sit-ups and crunches, how to get your form right, and which one should be part of your routine.
Meet the experts: Olivia Amato is a certified personal trainer and teaches bike, tread, boot camp, and strength classes for Peloton. Katharine Glazer is a personal trainer who has been certified. Amanda Hart is a personal trainer and holistic health coach who has been working in the fitness industry for 12 years. She is also certified by the NASM and ACSM. Kristina Earnest, CPT, has been teaching cycling and strength classes for more than ten years and started Kristina Earnest On Demand.
Which exercise is better: sit-ups or crunches?
According to Glazer, it depends on which muscle(s) you want to work on. “Every body has different needs and wants; there is no one size fits all.”
Sit-ups are better if you want to work out more than one muscle group at a time and get the most out of your money. Instead, are you trying to isolate your muscles more? You might like crunches. But some trainers like other abs exercises better than sit-ups and crunches (more on that soon!).
What sit-ups are good for
- Work out several muscle groups. Olivia Amato, CPT, a Peloton instructor, says that sit-ups can help you shape your abs (and more!) from many different angles at once when done correctly.
- Make stabilization better. Kristina Earnest, CPT, says that when you work out your core muscles, you are making your balance and steadiness better, which is also called “stability.” When you do sit-ups, you lift your whole torso off the ground, which works your abs, hip flexors, legs, back, and neck, which are all muscles that help you balance, Glazer says.
- Improved posture. Amato says that using all of those stabilizing muscles also helps you sit and stand up straighter.
- Get more flexible. When done correctly, sit-ups will loosen up your hips and spine. Amanda Hart, CPT, a holistic health coach, says that movement helps to make you more flexible. Better flexibility leads to other benefits, such as better performance and fewer injuries.
How to do a sit-up the right way
Put your knees at a 90-degree angle and your feet flat on the floor. Put your fingertips on the back of your ears and bend your elbows out to the side.
Breathe in deeply, then breathe out while tightening your core muscles and lifting your torso off the ground. Keep going until your chest is as close to your thighs as it can be. (But don’t worry if you don’t make it all the way there!)
With a smooth and steady motion, inhale as you lower back down to the starting position. That’s one rep. Do 10 reps to start, then add more as you get more comfortable.
Amato says, “I love doing sit-ups when I have a table to put my feet on or a workout buddy to hold my feet down with their hands.” “This usually makes sure that you have the right form because you don’t have to worry about keeping your feet on the ground while doing everything else.”
Different kinds of sit-ups to try
Boxer sit-up
To begin, lie on your back with your knees bent, your feet flat on the ground, and your hands in fists at your chest.
Take a deep breath in, then breathe out as you tighten your core muscles and lift your body off the ground. Keep going until your chest is as close to your thighs as it can get.
Punch forward, making sure your left arm is fully extended and your knuckles are facing forward while your palm is facing down.
Do the same thing with your right arm.
Bring your body back down to the floor slowly. That’s one rep.
Sit-up for sprinters
Lie on your back with your hands by your sides and your legs straight on the floor.
Sit up quickly, bringing your right knee toward your chest, your right arm back, and your left arm forward at a 90-degree angle.
Control the motion and do it again on the other side. That’s one rep.
Sit-up with a slam ball
Put your feet flat on the ground and bend your knees.
With your arms straight out in front of you, hold the slam ball above your chest.
To do a sit-up, tighten your core muscles and lift your torso. As you sit up, hold the slam ball over your head.
Bring yourself back down to the starting position, making sure you have control over the whole movement. That’s one rep.
The benefits of crunches
- Strong upper abs. Amato says that crunches are great for getting high rep counts because they focus on the upper abs. “I can do crunches over and over again because they’re a simple, low-impact exercise,” she says.
- Form is easy to learn. “With crunches, all you have to do is lift your head and shoulders off the floor while supporting your neck. This makes it easier to learn the move and do it without feeling sore muscles,” Amato says.
- Low chance of getting hurt. There isn’t much movement in crunches, so the risk of injury is also low. Hart says that if you lift higher off the ground, your hip flexors might start to work, which could put stress on your spine. You can strengthen your core without putting stress on your back by doing crunches, which don’t require much movement.
How to do crunches the right way
Keep your feet flat on the floor and lie on your back with your knees bent at a 90-degree angle.
Put your fingertips on the back of your ears, with your elbows bent and pointing to the side.
Take a deep breath in, tighten your core muscles, and then lift just your head and shoulder blades off the ground. Exhale as you do this. (Keep your chin tucked in but not touching your chest, and let your head be heavy in your hands to work your abs more.)
As you lower to the starting position, breathe in. That was one rep. Do 10 reps to start. If you feel like you know what you’re doing, do 20 to 30 more.
“Crunches can get boring sometimes, but I like to add a twist—pointing one elbow toward the opposite knee—to make them more interesting or crunch to the beat of a song,” Amato says.
Add these different kinds of crunches to your routine.
Bicycle crunch
Put your knees at a 90-degree angle and your feet flat on the floor while you lie on your back.
With your elbows bent and pointing out to the side, put your fingertips on the back of your head.
Breathe out and touch your left knee with your right elbow while keeping your right leg straight and rotating your torso.
Breathe in as you go back to the beginning and do it again on the other side. That’s one rep.
Crunch in reverse
To start, lie on your back with your hands at your sides and your feet off the ground at a 45-degree angle with your toes pointed. Put your lower back on the ground and keep your arms at your sides.
Push down into your arms, brace your core, and breathe out as you curl your knees toward your chest until your hips lift off the mat.
Take a deep breath and slowly go back to where you started. That’s one rep.
Frog crunch
Put your arms out to the sides and lie on your back.
Put your feet in a tabletop position, with your heels touching.
Put your legs out at an angle, keeping your heels close together.
Bend your knees and pull your heels back toward your body. That’s one rep.
What are the differences between crunches and other ab exercises?
Crunches and sit-ups are definitely worth your time, but that doesn’t mean they’re always the best. Some trainers even like other abs exercises, like planks, better. Why? Earnest says that both crunches and planks work the rectus abdominis and the obliques, but the plank also works the erector spinae, glutes, hip flexors, quads, and deltoids, making it a great compound movement that gives you more bang for your buck.
Earnest says that crunches and sit-ups can put a lot of stress on the neck, which you won’t feel as much in a plank.
Earnest says that you should also include rotational core exercises in your routine because they strengthen your lower back, make you more flexible, and work your obliques. This includes any exercise that makes your body turn, like Russian twists, wood chops, and reverse bicycles.
So, which is a better workout: sit-ups or crunches?
You can get stronger abs from both, but each exercise has its own set of pros and cons. Think about which one is best for your level of skill and safety, and then get to work.
Glazer says that sit-ups are more likely to hurt you because “it’s very hard to do the exercise correctly without rounding the lower back, which puts more stress on the lumbar spine.”
She says, “For this reason, trainers tend to tell their clients to stay away from sit-ups to lower the risk of injury.” Hart also likes crunches for this reason. She says, “The spine doesn’t bend and stretch as much, which means there is less chance of getting hurt.”
Crunches are great for shaping the top of your six-pack, but that’s also what makes them bad. Crunches only work your upper abs. Glazer says, “The problem with crunches is that your hips and legs are still, so you’re not fully activating your lower abdominals or your obliques.”
