How to do a crunch: Variations, tips and common crunch mistakes

For tight core muscles and more defined abs, you'll need our guide on how to do a crunch

Man doing crunch
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Do you really know how to do a crunch? Crunches, done right, are among the best abs workouts, even though they are among the most basic exercise moves. It's probably one you were taught in school, during gym or PE classes. But because it’s considered so simple, people often don’t put a lot of thought into performing the exercise correctly. 

Why do crunches at all, when there’s more complex, all-singing, all-dancing exercises out there? Because it works. Researchers from the University of Wisconsin, published by the American Council of Exercise, found traditional crunches had greater abdominal muscle activation than equipment-based exercises using the Ab Circle Pro, Ab Wheel, or other abdominal exercises like planking, decline bench curls or bicycle crunches. 

When it comes to the crunch (sorry), the most basic ab exercise is also one of the most effective. 


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Crunches work the upper abdominals, developing core strength to help you in a wide variety of moves and disciplines. In any physical activity, whether it’s football, boxing, rock climbing or dance, a strong core is vital for anyone undertaking any kind of regular exercise, and particularly those playing sport. 

Having a strong, flexible trunk (that’s the area around the abdominal muscles) is vital for success in sports. The abdominal crunch is a classic exercise that works the ‘abs’, just like a sit-up. However, unlike a sit-up, which involves raising your upper body, the crunch is about raising your head and shoulders.

 How to do a crunch 


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  • Getting the crunch right is all about body positioning. Lie flat with your fingertips behind your head, just above your ears. Your elbows should be in line with your chin or ears. 
  • Your legs should be together, bent at the knees, with both feet placed flat on the floor. They should remain together, flat on the floor, throughout the exercise. Don’t lift your legs! 
  • To perform the crunch, raise your head and shoulders off the ground, pushing your chest towards your hips. Your ‘abs’ should tighten during the movement. Pause, before returning to the starting position in a controlled manner.
  • The crunch is hard to get right, and many people make mistakes. Try not to push your head forward with your hands – the movement for the exercise should come from your abs, spine and lower back.

How to do a crunch: Common crunch mistakes


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“As you come up, tuck in your chin to lengthen back of neck and engage your abdominals,” says Sam Hull, top PT and pilates instructor at F45’s Tooting branch. “Slowly lift your head and shoulder blades off the floor, drawing the ribs down and in, when coming up to a crunch position.” 

Focusing on engaging your abs is important if you want to make the most out of the crunch. Hull recommends avoiding tension in your neck and shoulders, staying relaxed in your upper body to allow for maximum range of motion.

The crunch is a time-honoured method of sculpting your abs, but it’s falling out of popularity in some quarters, as some fitness experts theorise the act of curling your spine while lying on the floor risks injury because of the pressure put onto your discs. 


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A round-up of studies published in the Strength and Conditioning Journal says a clear consensus has not been reached, although crunches remain very effective in developing abdominal muscles. Little definitive evidence has been produced since the round-up’s publication in 2016. 

If you suffer from any pre-existing back pain issues, it’s best to avoid the exercise in favour of other ab moves like the plank. Otherwise, make sure you use our form tips above and incorporate the crunch into a programme of other trunk-strengthening exercises that do not put pressure on your back.

And finally, if you're trying to lose weight on your stomach, it's important to note that crunches alone aren't enough to get you there. You'll also need to incorporate exercises that burn fat into your workout routine, as well as considering factors such as diet, water and alcohol intake, and your sleep patterns.

Variation: Crunch with raised legs 


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This is a trickier alternative to the requiring greater core stability and control than the normal crunch.

  • Lie flat with your fingertips behind your head. Your elbows should once again be in line with your chin or ears. 
  • Your legs should be together, bent at the knees, elevated in the air at a right-angle to your torso. 
  • To perform the crunch, raise your head and shoulders off the ground, pushing your chest towards your hips as you would during the standard crunch. Your ‘abs’ should tighten during the movement. 
  • Pause, before returning to the starting position in the same way. 

More crunch variation guides: