Crunches vs. Sit-Ups: Which Abdominal Exercise Is Better?

Everyone wants to get more done in less time. And working out is no exception. So it makes sense to choose efficient exercises. 

Crunches and sit-ups are two classic ab exercises. Both of them have pros and cons. But which one is most efficient? Let’s have a look.

What’s the difference between crunches and sit-ups?

Some people use the terms interchangeably, but crunches and sit-ups are two different exercises. It's easy to understand the confusion. Both moves target the abdominals and involve ab-flexion from a supine or face-up position. 

The main difference between crunches and sit-ups is the range of motion and spinal position during each exercise. In a crunch, you curl your upper back off the floor vertebrae by vertebrae, but your lower back remains on the floor. In a sit-up, you curl your entire back off the floor, allowing a greater range of motion. 

What’s the proper way to do a crunch and a sit-up?

As with any exercise, proper form is critical to reaping the benefits of crunches and sit-ups. 

How to do a basic crunch 

1. Lie on the floor on a mat or another form of cushioning, like a carpet. 

2. Bend your knees and place your feet flat on the floor.

3. Interlace your hands behind your head at the base of your skull. 

4. Squeeze your shoulder blades together and keep your elbows wide. 

5. Exhale as you contract your abdominal muscles and slightly tuck your chin toward your chest. 

6. Curl your torso up toward your knees while keeping your feet and lower back pressed into the floor. 

7. Curl up until your lower back is off the floor, then hold the position briefly. 

8. Inhale as you slowly lower down with control. 

How to do a basic sit-up

1. Lie on an exercise mat with your knees bent and your feet flat on the floor. 

2. Clasp your hands lightly behind the base of your skull. Use your hands for gentle support; do not pull on your head or neck. 

3. Contract your abdominal muscles and exhale as you curl your torso off the ground. 

4. Inhale as you lower back down with control. 

What are the benefits of crunches? 

Crunches are a safe and effective way to strengthen the abdominal muscles. There are many variations of crunches, but they all share the same key benefits. 

Isolate the abdominal muscles 

Crunches have a shorter range of motion than sit-ups. That might seem like a disadvantage, but it depends on your fitness goals. Less range of motion means crunches are better at isolating the abdominals, which do all the work in this exercise. That's good news if you want to target, tone, and strengthen specific ab muscles. 

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Strengthen abdominals 

Crunches received top marks for their effectiveness in a study from the American Council on Exercise (ACE). The exercise strengthens the rectus abdominis muscle and the obliques. The rectus abdominis muscle is a large muscle that runs from the bottom of the breastbone to the pubic bone. It is segmented, which gives the appearance of a "six-pack." The obliques run along the sides of the torso from the ribs to the pelvis. 

According to the ACE study, crunches on an exercise ball were the third-most effective way to strengthen the rectus abdominis. The reverse crunch came in third place for strengthening the obliques. 

Increase abdominal endurance

Muscular endurance is the capacity for muscles to perform repetitive actions without tiring. It's different from muscle strength and is an important part of fitness and proper posture. 

A 2015 study found that even brief crunch training once a week improved adolescents' muscular endurance. The researchers concluded that crunches are a time-efficient way to increase abdominal endurance. 

Lower risk of injury 

Crunches may be safer than sit-ups for the spine. That's because crunches put less force and compression on the spinal discs. Crunches also place less demand on the hip flexors. These small muscles on the front of the pelvis attach to the lumbar spine. When they become overworked or too tight, they increase pressure on the lumbar spine and cause discomfort. 

What are the benefits of sit-ups? 

Sit-ups used to be a go-to abdominal exercise for many fitness enthusiasts. The military started using sit-ups as part of fitness testing in the 1920s. 

But their popularity has declined due to increasing evidence that they may do more harm than good. For example, the Army phased out sit-ups after a study found that the exercise has a higher injury rate than running or doing push-ups. A self-reported injury survey revealed that 56% of injuries sustained in the Army Physical Fitness Test were attributed to sit-ups. 

The main problem with sit-ups is their potential to cause lower back strain. Unlike crunches, traditional sit-ups activate the hip flexors. When they are too tight or overworked, as is a risk with sit-ups, they can pull on the lumbar vertebrae, causing low back pain. 

That said, sit-ups may offer benefits similar to crunches –– like increased abdominal strength and endurance –– for advanced exercisers. They might also provide additional advantages. 

Allow a greater range of motion

A sit-up requires you to lift your entire back off the floor. That means the exercise offers a greater range of motion –– and targets different muscles –– than crunches. Sit-ups can help reduce back pain and improve sports performance by engaging the hip flexors. 

Improve balance

Because more of your back is off the ground in a sit-up, your hips must do more work to balance and stabilize your body. This is especially true in some sit-up variations, such as the V sit-up. In the V sit-up, your feet also come off the floor. Advanced exercisers can benefit by training these small stabilizer muscles for improved balance.

Are crunches or sit-ups better for you?

Generally, crunches are the better choice for most people. They're easier to do correctly, have a lower risk of back injury, and are a more efficient exercise for training total core strength. 

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Written by:

Jody Braverman, CPT, RYT

Jody Braverman has worked in the health and fitness industry –– as a trainer, yoga teacher, nutrition and lifestyle coach, writer, and editor –– for more than two decades. She graduated with a B.A. from the University of Maryland and maintains several accredited certifications.

Edited by:

Lauren Savage, MA

Lauren Savage, MA, is a health editor at GoodRx, where she focuses on movement, exercise, and healthy aging. She aims to provide readers with the information they need to live healthier, more active lifestyles.

Reviewed by:

Sanjai Sinha, MD

Sanjai Sinha, MD, is a board-certified physician with over 20 years of experience. He specializes in internal medicine.

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