How To Do A Crunch: Form, Muscles Worked And Tips

The crunch is a floor exercise where you curl your head and shoulders off the ground by shortening your abs. Unlike a full sit-up, your lower back stays on the floor, which keeps the work on the rectus abdominis and takes the hip flexors mostly out of the movement.

It needs no equipment, takes up about as much space as a yoga mat and is one of the simplest ways to start training your core.

Crunch start and finish positions. The highlighted segments show the primary muscles.

Crunch Quick Facts

Primary Muscles	Abs (rectus abdominis)
Secondary Muscles	Obliques
Equipment	None (a mat makes it more comfortable)
Level	Beginner
Sets And Reps	2-3 sets of 12-20 reps

How To Do A Crunch

Lie on your back on a mat with your knees bent and feet flat on the floor, about hip-width apart.
Rest your fingertips lightly beside your ears, cross your arms over your chest or reach your hands toward your knees.
Brace your core and gently press your lower back into the floor.
Breathe out and curl your head, neck and shoulder blades off the floor, bringing your ribs toward your hips.
Pause for a second at the top while squeezing your abs.
Lower back down slowly until your shoulder blades touch the floor, then repeat.

Crunch Form Tips

Think about shortening the distance between your ribs and hips rather than sitting up.
Keep a fist-sized gap between your chin and chest so your neck stays relaxed.
Move slowly. A two-second lowering phase makes each rep harder and safer.
Breathe out as you curl up and breathe in as you lower.

Common Mistakes To Avoid

Pulling on the neck. Yanking your head forward strains the neck. Your hands should only support your head lightly.
Using momentum. Swinging up fast lets your hips and arms do the work instead of your abs.
Sitting all the way up. Rising past your shoulder blades turns it into a sit-up and shifts work to the hip flexors.
Arching the lower back. Letting your back lift off the floor takes tension off the abs.

Muscles Worked

The rectus abdominis, the "six-pack" muscle running down the front of your stomach, does most of the work as it bends your spine forward. The obliques along your sides help stabilize the movement.

Crunch Variations

Reverse Crunch: Curls the hips up instead of the shoulders.
Bicycle Crunch: Adds a twist to bring in the obliques.
Cable Crunch: A kneeling version you can load with more weight.
Leg Raise: Targets the lower part of the abs.
Plank: Trains the abs to hold still instead of bend.

How Many Sets And Reps Should You Do?

Start with 2-3 sets of 12-20 reps. Use a load you can move with clean form for every rep, and add weight or reps once the top of the range feels controlled for all sets.

Frequently Asked Questions

Do Crunches Burn Belly Fat?

Crunches strengthen your abs but do not burn fat from your stomach specifically. Losing belly fat comes from your overall diet and activity. Crunches make the muscle underneath stronger and more visible as body fat comes down.

How Many Crunches Should You Do A Day?

You do not need to do them every day. Two to four sessions per week of 2-3 sets, each taken close to fatigue with good form, is plenty for most people.

Are Crunches Better Than Sit-Ups?

Crunches keep the lower back on the floor and focus on the abs, while sit-ups use more hip flexor. Many people find crunches easier on the back.

More Exercise Guides

This guide is for general information only. Check with your doctor before starting a new exercise program, and stop if you feel pain. Read our medical disclaimer.