You’re not the only one who isn’t sure what the difference is between sit-ups and crunches. They both make your core stronger, but it can be hard to understand how they are different and what each one is good for.
Katharine Glazer, CPT, says, “The main difference between the two is that in a crunch, the lower back never leaves the floor.” A crunch is basically 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 a lot of different muscles at once, including the rectus abdominis, hip flexors, transverse abdominis (deep core muscles), obliques (side abs), and lower back muscles. When you lift your torso all the way off the ground, you use more muscles.
The debate over crunches and sit-ups is a lot more complicated than that. Experts say that both sit-ups and crunches have pros and cons. Keep reading to find out how to do them correctly and which one should be in your routine.
Meet the experts: Olivia Amato is a certified personal trainer and teaches Peloton classes in biking, treadmilling, boot camp, and strength training. Katharine Glazer is a personal trainer who has been certified. Amanda Hart has been a personal trainer and holistic health coach for 12 years. She is certified by the National Academy of Sports Medicine (NASM) and the American College of Sports Medicine (ACSM). Kristina Earnest, CPT, has been teaching cycling and strength classes for more than ten years and started Kristina Earnest On Demand.
Which is better: sit-ups or crunches?
Glazer says it depends on which muscle(s) you want to work. “Every body has different needs and wants; there is no one-size-fits-all solution.”
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If you want to get the most out of your money and work more than one muscle group at a time, sit-ups are better.
Instead, are you trying for intense muscle isolation? You might like crunches.
But some trainers like other abs exercises better than sit-ups and crunches (more on that in a minute!).
The good things about sit-ups
- Work out *many* muscle groups. Olivia Amato, a Peloton instructor, says that doing sit-ups with the right form can help you sculpt your abs and other muscles from many angles at once.
- 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.” According to Glazer, sit-ups work your abs, hip flexors, legs, back, and neck, which are all muscles that help you keep your balance.
- Better posture. Amato says that using all those stabilizing muscles also helps you sit and stand up straighter.
- Get more flexible. When done correctly, sit-ups will loosen up your spine and hips. Amanda Hart, a holistic health coach and CPT, says that motion helps to make people more flexible. Better flexibility leads to other benefits, such as better performance and fewer injuries.
How to do a sit-up the right way
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- 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 so they point out to the side.
- Take a deep breath in, then exhale 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 be. (But don’t worry if you don’t make it all the way there!)
- As you go back down to the starting position, breathe in and out in a smooth, steady motion. That’s one rep. Start with 10 reps and add more as you get better.
Amato says, “I love doing sit-ups when I can anchor my feet on a table or have a workout buddy hold my feet down with their hands.” “This usually makes sure that your form is correct because you don’t have to worry about keeping your feet on the ground on top of everything else.”
Different kinds of sit-ups to try: the boxer sit-up
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- 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 be.
- Punch forward, fully extending your left arm so that your knuckles are facing forward and your palm is facing the ground.
- Do the same thing with your right arm.
- Slowly bring your body back down to the floor. That is one rep.
What are the benefits of crunches?
- Strong upper abs. Amato says that crunches are great for high rep counts because they focus on the upper abs. She says, “I can do crunches all the time because they’re a simple, low-impact exercise.”
- Form that is easy to learn. Amato says, “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 hurting your muscles.”
- Little chance of getting hurt. The risk of injury is low because crunches don’t move very much. Hart says that if you lift higher off the ground, your hip flexors may start to work, which puts stress on your spine. Crunches are a good way to strengthen your core without putting too much stress on your back because they don’t require much movement.
How to do crunches the right way
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- Keep your feet flat on the floor and bend your knees to a 90-degree angle.
- With your elbows bent and pointing out to the side, touch the back of your ears with your fingertips.
- Take a deep breath in, tighten your core muscles, and then lift only your head and shoulder blades off the ground. As you rise, breathe out. Put your chin down but not on your chest, and let your head be heavy in your hands to work your abs harder.
- Take a breath in as you lower yourself back to the starting position. That’s one set. Do 10 reps to start, and if you think you can do more, do 20 to 30.
“Crunches can sometimes feel repetitive, but I find that when they do, I just add a twist—pointing one elbow toward the opposite knee—to spice things up or crunch to the beat of a song,” Amato says.
So, which is a better workout: sit-ups or crunches?
Both can help you strengthen your abs, but each one has its own pros and cons. Decide which one is best for your skill level and safety, and then get to work.
Glazer says that sit-ups are more likely to cause injury 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 that “trainers tend to have their clients avoid sit-ups to lower the risk of injury.” That’s another reason Hart likes crunches. She says, “The spine doesn’t bend and extend 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 why they don’t work. Crunches work only 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 abs or your obliques.”
