Crunches vs. Sit Ups – Which is better for abs?

What’s the difference between the two classic ab exercises?

The two most well-known ab exercises are crunches and sit ups. Even people who know nothing about working out have heard about these exercises. Sometimes they are mixed since movements are very similar.

What is the key difference between traditional sit ups and crunches?

We are going to compare them here. You will learn their pros and cons, differences and what the correct forms are.

Sit ups

Sit ups benefits

Engages the core well

The sit up is a somewhat compound exercise that works for multiple muscle groups at once. The main target is the rectus abdominis, which gives the six-pack look on a lean stomach. That is the primary muscle that pulls the weight of the upper body up during motion.

But, other core muscles are activated as well, such as the oblique (side abs), hip flexors, and lower back muscles. These muscles stabilize the torso during motion (stabilizers) and help to execute the movement.

Other muscles, such as the neck, legs, and chest, are activated, but the effect on them is neglectable.

A strong core is vital for correct posture and helps to perform better in physical activities.

Muscles worked – Credit:

Longer range of motion

Sit ups compared to crunches have a more extended range of motion. That means the abdominal muscles stretch longer and have to work harder, which leads to improved power and muscle mass. It also helps to build functional strength.

Versatile and suitable for advanced athletes

There is a lot of dispute about if sit ups are bad or not. (Later I’m going to tell you my opinion.) But, if we check out an ab workout of a professional MMA fighter or boxer, this workout is always included. Why? Because they work! This abdominal exercise builds a rock-solid midsection that is required for fighting in the ring. And the sit up bench is still one of the most beneficial exercise equipment for abs.

As part of your strength training workout, add sit-ups after lifting weights or performing squats

What are the cons of sit ups?

Not for everyone

People having weak or back injuries, spine or neck problems shouldn’t do this training without the permission of their doctors. This exercise puts stress on these areas and may worsen the conditions. You may have difficulty performing this movement without swaying your lower back, which increases the strain on your lumbar spine.

Proper form is critical

As I said before, people complain a lot about the pain which mainly comes from the incorrect form. They have neck or back pain, or simply don’t enjoy the benefits of the exercise, because they do it incorrectly. They pull their neck muscles or shoulders, bend their back too much, etc that leads to too much pressure on the posterior. Another reason for pain and poor performance is that they have weak core muscles which also increase the risk of injuries.

Doesn’t burn much belly fat

Sit ups are abdominal strength training exercises that may more burn calories than crunches, but just by doing these core exercises, we can’t burn belly fat. To get a lean stomach, the most critical step is altering the diet and do cardio workouts to reach the daily calorie deficit.

How to do unanchored sit ups correctly?

  1. Lie on the ground, bend your knees, and plant your feet on the ground so that they stabilize your lower body.
  2. Place your hands behind your head, but don’t pull your neck during the entire move!
  3. With the power of your abs, slowly lift your upper body with straight back towards your knees. In this phase, exhale.
  4. Lower your upper body with straight back by controlling the motion with the power of your abdominal wall. In this phase, inhale.
  5. Do at least 10 reps, but that depends on your fitness level.

The most important is to control the entire movement, keep your balance and use your core. Don’t use the momentum or cheat. This way, you get complete core training and avoid injuries.

Even though it may be tempting to get your core workouts out of the way quickly, take your time and do it steadily.



What are the crunches benefits?

Better focus on abs

It’s an isolated movement. Abdominal crunches are shorter moves that don’t require much engagement from the stabilizer and supporting muscles. They are more isolated exercises that target mainly the rectus abdominis muscles that give the six-pack abs look. But, they also activate the back, hip flexors, and obliques. It provides intense muscle isolation.

Because of the isolation, someone who already has a lean stomach quickly sees results by doing the crunch exercise regularly.


They are easier to learn and perform, so they are more suitable for beginners.

Lower back friendly

It doesn’t put as much stress on the spine and neck, but the correct form is also essential here.

Cons of crunches

Short moves

Because of the shorter range of motion, they don’t build such power as sit ups. (This is my personal experience, I know others who say the opposite, but I still prefer abs exercises with a longer range of motion that improve core stability and endurance.) However, they are suitable for building the size of the ab muscles.

Note: A reverse crunch or curl is a modification of the classic crunch and is excellent for targeting the core muscles more effectively.

Doesn’t work the entire core

Yes, some core muscles, such as obliques and lower back, are engaged when we crunch up, but they aren’t the best to strengthen your core as a whole.

Not for burning stomach fat

Such isolated exercises are inefficient for burning fat. For weight loss, you should focus on healthy nutrition instead.

How to do crunches properly?

  1. Lie flat on the floor with your knees bent and with your feet flat.
  2. Place your fingers behind your head, but don’t pull your head during the workout.
  3. Only with the power of your abdominals curl your upper part of your back towards your knees. Lift your shoulder blades, but keep your hips on the floor. (When you reach the maximum muscles contract, you can stop for a moment and squeeze your abs for maximum benefits.) In this phase, exhale.
  4. By exhaling slowly, lower your upper body backward to the starting position, but don’t let your head touches the floor.
  5. Perform as many reps as required, but 10 is the minimum.

Which is better sit up or crunch?

As you see, both exercises have their pros and cons. I don’t want to say this or that works. I include both in my ab workout. To gain muscle, we need a combination of exercise (comprehensive workout) and a healthy diet.

What do you think? Give a vote for your favorite!

Which is better?


Which is better for losing belly fat: crunches or situps?

While no single exercise can burn just belly fat, regular exercise in combination with a healthy diet can help to reduce overall body fat. It is not possible to specifically burn belly fat through abdominal exercises like crunches and sit-ups, but they can deliver benefits to the belly by making it appear flattered and more toned.

How many sit ups or crunches a day for abs?

As expected, there isn’t one exact number of repetitions you need to do to end up with nice abs. Yet these exercises are an excellent way to increase your fitness level and build core strength. It is recommended that you combine three sets with 25 to 50 repetitions each for building and sculpting abs.

Written by Imre

Imre has been working out for over 20 years. He likes all sorts of strength training and boxing. Since he's a busy father he works out only at home.