How to do a reverse crunch: Form tweaks, common mistakes and more workout tips

The reverse crunch is a sure-fire way to work out your lower abdominal muscles, making it the best exercise for lower abs

Reverse crunch
(Image credit: iStock)

Crunches and sit-ups are some of the best core workouts. But whilst great for honing your upper abdominal muscles, these classic fitness moves can leave your lower abdominals wanting. 

Learning how to do a reverse crunch is a great way to complete the set, ensuring you don't develop any muscular imbalances when training your core. 

Your lower abdominals help when using your core to walk, run, twist and rotate in everyday life, so the reverse crunch is great exercise to help with functional fitness. Along with the rest of the "six pack" muscle group, your lower abdominals will also look great in the mirror.

The reverse crunch, as the name implies, is the opposite of the traditional crunch: rather than keeping your legs and feet still and crunching your chest and torso inwards, you lie flat on your back, keeping your shoulders firmly on the floor or mat, and crunch the lower half of your body instead. This recruits a lot of muscles in your lower body, including your hip flexors, which makes it a great exercise to add into your routine if you’re looking for a stronger core. 

And why wouldn’t you be? Researchers from Harvard Medical School have found a stronger core provides benefits in both sport and everyday life. A strong core provides relief from back pain day-to-day, as well as increased strength and mobility when bending, twisting, lifting and even sitting down at your desk. 

(Image credit: iStock)

For fitness fans and athletes, training your core provides the same benefits when, for example, twisting your body to kick a football or throw a right hook. Almost all dynamic full-body movements make use of your core, and there’s very few exercises that activate your abdominal muscles as much as the reverse crunch does (according to the journal Physical Therapy). 

To get started, check out our how-to guide below, and follow our breakdown of form tips and variations to start carving a stronger core for yourself.   

How to do a reverse crunch

Reverse crunch

(Image credit: Future)

This hip flexor and core strength ‘crunch’ variant makes your lower body muscles do the work. 

  • Lie flat on your back with your arms by your sides, palms on the floor. Make sure your abs are drawn in and your legs and feet are together.  
  • Without moving your upper body at all, raise your hips and pull your knees towards your chest, bending them in the process. 
  •  Return to the starting position to complete one repetition. 

How to do a reverse crunch: Common reverse crunch mistakes 

Reverse crunch

(Image credit: iStock)

Reverse crunches are a simple move to learn, but difficult to master: any exercise reliant on curving your spine repeatedly has the potential for injury. You need to be careful when performing this move, as it’s not suitable for pre-existing sufferers of lower back pain. 

When it comes to maintaining perfect form, there’s a few things to bear in mind. “Ensure your legs are in a 90 degree position so that your shins are parallel to the floor”,  says Sam Hull, top PT and pilates instructor at F45’s Tooting branch. “Exhale as you engage your lower abs. Hold for a beat at the top of the movement and then slowly roll back through the spine to the start position. 

“When performing the reverse crunch, it also helps to engage your glutes and press your arms into the mat.” The instability of the movement can provide an additional challenge: as you struggle to keep yourself steady using only your core, it helps to work your abdominal muscles even more. Therefore, it’s important to do the move slowly and under control in order to get the most from this muscle-building move. 

 Variation: Reverse crunch kick-up 

Reverse crunch

(Image credit: Future)

If you’re feeling adventurous, try this variation on the classic reverse crunch – it adds in a dynamic kick for a greater cardiovascular workout.

  • Lie flat on your back with your arms by your side, your core braced, your legs together – bent at the knees – and your feet flat on the floor. 
  • Raise your hips and pull your knees towards your chest to perform a reverse crunch. 
  • Keep the movement going by kicking your legs out straight. As you extend your legs straight, your lower back should raise off the ground and your backside should be in the air. As you finish this movement, the tips of your toes should be in line with the top of your head. 
  • Return to the starting position to complete one repetition. 

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Matt Evans
Matt Evans

Matt Evans is an experienced health and fitness journalist and Channel Editor at Fit&Well. He's previously written for titles like Men's Health and Red Bull, and covers all things exercise and nutrition on the Fit&Well website. 

Matt originally discovered exercise through martial arts: he holds a black belt in Karate and remains a keen kickboxer and runner. His top fitness tip? Stretch.