Sit Ups vs. Crunches – Which One is Better and what is the difference?

Flat stomach and good abs are probably the pinnacle of fitness achievement for anyone who has started with a diet and workout regimen. Although it goes beyond saying that a trim and slim core is far more appealing than those unflattering stomach rolls, a strong core will also improve your posture and make your exercises more efficient while remaining injury-free. Having said that, it is fair to say that the abs are probably the most stubborn and most difficult muscles to tone (especially for women!) and that a six-pack comes at a serious price of watching your diet and training to your limits. So how do you square the debate between sit ups vs. crunches?

Sit Ups And Crunches

Presuming that you’ve cut down on all the food that makes your tummy chubby and you are now looking for a way to see those attractive ab-delineating lines, it still goes without saying that you need to be prepared for some serious sweating. The reason behind the sweat? Lots of and lots of sit ups and crunches!

Although all forms of exercise tend to make your core stronger, you won’t see that six-pack of yours without ab-targeted workouts. You’ve all probably heard of sit ups and crunches, but you’ll be surprised how many people either confuse them and think of them as the same exercise or are not quite sure what makes them different. If you are one of them, stick around while we take a closer look and compare these two ab-splitting exercises. It’s time for the sit ups vs. crunches “duel”.

What is the difference between crunches and sit ups?

When it comes to crunches vs. sit ups, the main difference is the muscles they target. Although they are both ab-working muscles, sit ups, unlike crunches, target multiple muscles at once. Unfortunately, neither of them targets belly fat directly (you need to stay out of the kitchen and go though the hell of cardio for that!).

The good thing about your core is that you will target some of the muscles with virtually every other bodyweight workout. Take for example squats or lunges – both contribute towards a stronger core, beyond their primary purpose.

What muscles do sit ups work?

Sit ups work the abs and a range of other muscle groups like the chest, lower back, hip flexors and neck. However, you shouldn’t dread building additional muscles, as muscle cells, due to their higher metabolic activity compared to fat cells, will make you burn more calories (and consequently fat) even when you are resting, which will bring you a step closer to a shredded abdomen.

What muscles do crunches work?

Crunches work by the principle of intense muscle isolation. They only work the abdominal muscles, therefore making them the most popular exercise for those trying to get a six-pack. They are also a perfect exercise for developing a strong core, which includes the lower back muscles and obliques. And a strong core translates into better posture and improved balance.

The sit up vs. crunches discussion inevitably breaks over the benefits of each of these exercises, which (and this cannot be stressed enough) will be significantly reduced if proper form is not maintained. So let me get back to the opening question:

Sit ups vs. crunches – which one is better? Well, let’s have a closer look at how these exercises work and then compare them one against the other.

What are the benefits of crunches and how to do a proper crunch?

Sit Ups Vs. Crunches 1

The crunch works by strengthening the rectus abdominis by flexing it. Although in performing crunches you don’t go as high as with the full sit up, this primary abdominal muscle activates during the first 30-45 degrees of movement, or just at the point when you lift the shoulders off the ground.

The crunch has a smaller range of motion compared to the sit up, but that is not necessarily a bad thing as it works your core without putting stress on your back.

One study published in the Journal of Strength and Conditioning Research found out that the Ab-slide exercise shows higher electromyographic activity across the external oblique, upper rectus abdominis and lower rectus abdominis, and is therefore slightly more effective than the crunch. However, the study also concluded that the crunches show significant activity as well, and should therefore not be excluded.

Of course, you won’t see any of the benefits of crunches if you fail to do them correctly. So in order to maintain proper form, follow the steps below.

Crunches also build endurance in abdominal muscles. By being an isolated exercise, they help achieve abdominal endurance faster and more effectively when compared against other ab exercises. As the purpose of your abs is to stabilize your mid-section, help you have a good posture, and support you when lifting heavy objects, one of the best benefits of crunches is that they help you achieve exactly that – which makes them quite the functional exercise.

How to do a proper crunch?

  1. Lie down on your back and bend your knees
  2. Put your hands behind your head or cross them so that palms are touching opposite shoulders
  3. Draw in your belly button towards your spine and lift your head, neck and shoulders off the floor (no higher), exhaling while going up.
  4. Pause, inhale, and return to the staring position. Make sure that your feet, low back and tailbone never lose contact with the ground as you roll up and down.

What are the benefits of sit ups and how to do a proper sit up?

Crunches Vs. Sit Ups

As I already mentioned, sit ups work more muscles in your body as opposed to abs only. They are a bodyweight exercise, just like crunches, but the fact that they engage multiple muscle groups means that they are more beneficial for toning your body and developing functional strength compared to crunches. Another of the great benefits of doing sit ups is that they do a great job at stabilizing your muscles and strengthening your core while protecting your spine.

Doing sit ups will help you increase your range of motion and flexibility, which will in turn help you maintain a good posture and reduce the risk of back injury or strain.

Here is how to perform a full sit up:

  1. Bend your knees and place your feet flat on the floor
  2. Put your hands behind your head or cross them to opposite shoulders
  3. Draw in your belly button towards your spine
  4. Lift your upper body pulling up from the floor until your elbows reach the knees. Exhale while lifting up.
  5. Pause for a second, and then slowly bring your upper body back to the floor. Inhale while lowering.

How about different varieties of each?

When considering each exercise, it is important to note that the crunch offers a far more versatile training program if you know how to vary the basic movement. We published an entire article, with a free video from our workout program, where you can gather some ideas on doing a variety of crunches or a palate of other ab exercises, so make sure to take a look.

Ab exercises

The sit up, on the other hand, is not an easy movement to modify. You can hold one dumbbell in your hand in order to increase the resistance on your abs and lower back, or perhaps extend your arm as you reach the highest point going upwards. Another option would be to make a slight twist with your core and therefore target your obliques too.

If you need a comprehensive program that includes some of the most advanced abdominal workouts incorporated across a number of bodyweight training sessions, make sure to check our platform Fitness Updated, where you can find complete nutritional breakdown, recipes, and smart bodyweight training videos.

Sit ups vs. crunches – the verdict

While sit ups engage more muscles, they undoubtedly put more strain and stress on your spine, including the neck. However, if not done with proper form, crunches can also lead to back pain, especially in beginners.

As for their input in achieving the desired flat belly, they are both excellent for developing and strengthening core muscles. But, if you are still looking for a definite answer to the question “Sit ups or crunches for flat stomach”, the answer goes beyond the crunches vs. sit ups debate. No ab exercise burns fat, and getting a flat tummy requires combination of these exercises with a healthy, low-calorie diet as well as regular cardio exercises.

As part of a comprehensive exercise routine, both the crunch and the sit up can help you lose body fat by contributing to an increase of your metabolic rate, as well as a slight but significant increase in muscle tissue around your abdomen. They alone won’t shrink your tummy, but will speed the weight loss process dramatically – and as you lose belly fat, your newly strengthened abs will start showing.

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