Crunches are an excellent exercise to strengthen the abdominal muscles. Many people do them to also burn off the fat that covers the abs. As a result, they want to know how many calories crunches burn.
In this article, I reveal the answer to that question. I will also explain why doing crunches for calorie burning is not a wise strategy – and what you should do instead.
Why Do Crunches?
The crunch has been a standard exercise to work the major muscle of the core, the rectus abdominis, for decades. Many people consider it to be a safer alternative to the sit-up because you are not having to bring your lower back completely off the floor.
The function of the rectus abdominis is to draw the torso toward the lower body. It does this by contracting. That is exactly what you do when you are doing an ab crunch, making this a very good exercise to move the muscle through its full range of motion.
The Best Way to Do Crunches
The best way to do a crunch is not lying on the floor. That’s because that version of the exercise is too difficult for most people to do with the correct form. The position of the torso relative to gravity maximizes the resistance beyond most people’s strength level. This usually results in incorrect form, too few repetitions, and a range of motion that is too short – basically head lifts only.
By changing the angle of the torso you are able to reduce the resistance to a more manageable level. One way to do this is by doing your crunches on an incline bench that is set at around 45 degrees.
An even better option is to do crunches on a cable machine. Here is how to do it with proper form:
- Place a weight bench with back support about three feet in front of a cable pulley machine, facing away from it.
- Set the pulley at its highest position and put a rope handle on the end of the cable. Set a weight that will allow 30 reps.
- Grab the handles and sit on the bench so that your hands are above your head.
- From this starting position, crunch down so that your elbows come down to your knees. Tense the abs in the bottom position.
- Reverse under control to return to the start position.
How Many Calories Do Crunches Burn?
It is possible to calculate how many calories you burn when doing different exercises by using something called the metabolic equivalent of task (MET) This is a value that has been assigned to that exercise.
The MET for crunches is five. To calculate the calorie burn we have to use the following formula …
MET x body weight in kilograms x 0.0175 times x duration
Let’s plug in some numbers for crunches for a 90 kg person …
5 x 90 x 0.0175 x 10 = 78.75
From this, we see that you will burn around 79 calories if you do crunches for 10 minutes straight.
That’s a lot of crunches!
Let’s break this down further.
If you do crunches for one minute straight, you will burn 7.9 calories.
The average person will be able to do 23 crunches in a minute. So, when we divide 7.9 calories by 23 we get 0.34.
This tells us that the average person will burn 0.34, or a third, of a calorie with every crunch.
The exact number will change with your weight, the resistance you use, and your gender. [1]
Why Doing Crunches for Weight Loss Doesn’t Work
Now that we have worked out how many calories you burn when you do crunches, allow me to explain why it doesn’t matter.
Crunches are good exercises to work your core muscles. but they are a very inefficient way to burn off belly fat.
Even if you could spot reduce belly fat (more on this in the next section), doing crunches is a poor way to go about it. We have established that 10 minutes of crunches will burn 79 calories, on average. Remember that is 10 minutes of non-stop crunches.
To burn just 200 calories, you will have to do about 30 minutes of crunches – if you were doing 23 crunches per hour, that means you’d have to pump out 690 crunches.
All of that work would see you lose one pound of body fat in 17.5 days!
But only if you disciplined yourself to do 690 crunches every single day.
That is not a very good return on your exercise investment.
The Spot Reduction Myth
Contrary to what many people continue to believe, it is not possible to lose body weight from a specific area of the body. That means that you will never get a flat belly just from doing crunches.
As we have already found, standard crunches will help you to strengthen your core and build your ab muscles. But it is a very inefficient calorie burner.
In order to get rid of stored body fat, you need to do the exercises that burn the most amount of calories. Those calories will come from all over your body, not just your belly. [2]
The Best Calorie-Burning Exercise
The best calorie-burning exercises are those that allow you to sustain a high-calorie burn without stressing your body. As a personal trainer, I have tried every type of calorie-burning cardio exercise that has ever been invented. At the end of the day, my all-time favorite calorie burner is the rowing machine.
The rowing machine allows you to work 80% of the muscles in your body, producing a higher calorie burn than most other cardio exercises. It is also a very joint-friendly exercise, making it suitable for people with mobility and joint problems.
A 90 kg person will burn around 440 calories after a vigorous 30 minutes on the rowing machine. That is more than double the calorie burn from doing crunches for a half hour nonstop. [3]
Training with a rowing machine will burn around 15 calories per minute (900 calories per hour). This will fluctuate with the exercise intensity. It will also increase your metabolic rate for several hours after your workout, depending on the duration of time spent exercising.
To ramp up your calorie burn even further, I recommend doing HIIT rowing workouts. This involves alternating high and low-intensity rowing for multiple rounds.
Frequently Asked Questions
How many calories per hour will you burn doing crunches?
If you do 23 crunches per minute, you will burn 7.9 calories in a minute. If we multiply this by 60, we get 474 calories an hour.
Will crunches build muscle mass?
The abdominal muscles do not have much capacity to build muscle mass. But they will get a little bit thicker when you do crunches. Your abs will also get stronger when you do crunches.
What should I eat for a flat belly?
Eating for a flat belly requires cutting out sugary foods, reducing alcohol intake, and removing sugary drinks from your diet.
Summary
You will burn about a third of a calorie with every crunch that you do. A far more effective strategy to lose belly fat is to get on the rowing machine and perform HIIT-style training. This will burn around 15 calories per minute.
I recommend doing 3-4 HIIT workouts on the rowing machine every week to burn body fat.
References
- https://en.wikipedia.org/wiki/Metabolic_equivalent_of_task
- Ramírez-Campillo R, Andrade DC, Campos-Jara C, Henríquez-Olguín C, Alvarez-Lepín C, Izquierdo M. Regional fat changes induced by localized muscle endurance resistance training. J Strength Cond Res. 2013 Aug;27(8):2219-24. doi: 10.1519/JSC.0b013e31827e8681. PMID: 23222084.
- https://www.healthline.com/nutrition/rowing-for-weight-loss
