A reverse crunch starts on your back with your hips and knees bent to about 90 degrees. Your stomach muscles curl your pelvis up so your knees travel toward your chest and your hips lift a short way off the floor, then you roll back down slowly. Your head and shoulders stay on the mat. The curl does the work. Your legs should not swing.

How to do the reverse crunch

Lie face up on a mat with your arms straight along your sides, palms resting on the floor.
Lift your legs so your hips and knees are both bent to about 90 degrees, with your knees above your hips.
Breathe out and use your stomach to curl your knees in toward your chest, so your hips and lower back peel a little way off the mat. Your head, shoulders and upper back stay down and relaxed.
Breathe in and roll your spine back down slowly, one section at a time, until your hips rest on the mat and your knees are back above your hips.
Repeat at a steady pace, keeping your feet off the floor between reps.

What you should feel

Work low in your stomach as it curls your pelvis up, and some effort at the front of the hips. Your neck and shoulders stay easy.

Common mistakes

Throwing the legs to swing the hips up, instead of curling them.
Pushing down hard through your arms to lift the hips.
Letting your hips drop back to the mat rather than lowering them.
Lifting your head or holding your breath.

How often

Many programs use 2 to 3 sets of 8 to 12 slow reps, a few days a week. Your physio will adjust this, and may start you on an easier core exercise.

Stop and check with your physio if

Pain in your lower back, or pain, tingling or numbness that runs down a leg.
A bulge along the middle of your stomach or in your groin, or pain around a surgical scar.
You leak urine, or feel heaviness or dragging in your pelvis.

From the clinic

The lift is small. Your hips only need to clear the mat by an inch or two, and a slow roll down is where most of the control comes from. If you can only get the hips up by swinging your legs, go back to the tabletop leg lift or the dead bug for a while. If you have high blood pressure, breathe steadily through every repetition and never hold your breath.

If you have osteoporosis or low bone density, or have had a spine fracture, skip reverse crunches unless your physio has cleared them. Osteoporosis programs often limit repeated forward bending of the spine under load, and a reverse crunch is exactly that movement.

Check with your physio first if you have a hernia, a separation of the stomach muscles after having a baby (diastasis recti), or have had stomach or back surgery. Curling against the weight of your legs can raise the pressure inside your stomach, which pushes down on your pelvic floor. If you already have leaking or a heavy feeling in the pelvis, ask your physio for a gentler option. If you are pregnant, leave reverse crunches out unless your physio or midwife says they are fine, as they strain the stomach muscles while those muscles are stretching. If you are pregnant and past the first three months, check with your physio before exercising flat on your back.

If you have had a hip replacement, get the go-ahead from your surgeon or physio before you try reverse crunches. Curling the knees in toward your chest bends the hip well past a right angle, and many surgeons ask you to avoid that for the first months after some operations.

Written and checked by the PocketPhysio editorial team. Last updated 2026-09-26.

This page is general education, not a diagnosis or a personal treatment plan. If you have pain, an injury or a health condition, see a physiotherapist or doctor before starting new exercises.

Reverse crunch