A sit-up takes you from lying on your back all the way up to sitting, by curling your spine forward one section at a time. Your knees stay bent and your feet stay down. The stomach muscles start the curl, and the hip flexors at the front of the hips finish it. Because the whole spine bends forward under the weight of your upper body, sit-ups ask more of the neck and lower back than a crunch, where your lower back stays on the floor.

How to do the sit-ups

Lie face up on a mat. Bend your knees and set both feet firmly on the mat, hip width apart, pressing them down to steady your lower body.
Cross your arms over your chest with each hand on the opposite shoulder. Or rest your fingertips lightly behind your ears, as in the video, without pulling on your head.
Breathe out and curl up slowly: head first, then your shoulders, then your upper and lower back, until your chest comes up toward your knees.
Keep your feet planted all the way up. If they lift off, you are using momentum rather than your stomach muscles.
Breathe in as you roll back down with control, lower back first, then upper back, then head.

What you should feel

Your stomach muscles working hard, most of all at the start of the curl, then the front of your hips as you come up to sitting. You should not feel strain in your neck or pain in your lower back.

Common mistakes

Pulling on your head with your hands, which bends the neck forward.
Jerking or swinging up instead of curling.
Feet lifting off the floor as you rise.
Flopping back down instead of lowering slowly.
Holding your breath during the lift.

How often

Many programs start with 1 to 3 sets of 5 to 12 slow sit-ups, a few days a week, stopping when you can no longer curl up without jerking. Your physio will adjust this, and may give you a crunch or another core exercise instead.

Stop and check with your physio if

Neck pain, or pain, tingling or numbness spreading into an arm.
Pins and needles in your arm or hand that do not go away after you stop, or part of your arm or hand goes numb. Get medical advice the same day. If one side of your face or body suddenly goes numb or weak, or your speech becomes slurred or muddled, call emergency services, even if it goes away.
Lower back pain, or pain, numbness or tingling traveling down a leg.
A new bulge along the middle of your stomach, or pain around a scar from surgery.

From the clinic

For most people the neck complains first. Crossing your arms on your chest takes your hands away from your head, so you cannot pull on it. If you keep your hands by your ears as in the video, let the fingertips just rest there and keep your elbows open rather than drawing them together at the top. If a full sit-up is too hard or bothers your back, abdominal crunches and the dead bug work the stomach while your lower back stays down.

If you have osteoporosis or low bone density, or have had a spine fracture, skip sit-ups unless your physio has cleared them. Osteoporosis programs often limit repeated forward bending of the spine under load, and a sit-up is exactly that movement. A disc problem in your lower back, or back pain that travels down a leg, is another reason to ask your physio before starting.

Ask your physio first as well after stomach or back surgery, with a hernia, or with a separation of the stomach muscles after having a baby (diastasis recti). Sit-ups also push down hard on the pelvic floor. If they make you leak urine or give you a heavy, dragging feeling in the pelvis, stop and ask your physio for a gentler option. If you are pregnant, leave sit-ups out unless your physio or midwife says they are fine. They strain the stomach muscles while those muscles are stretching, and after about 16 weeks the NHS advises against lying flat on your back for long, because it can make you feel faint.

Written and checked by the PocketPhysio editorial team. Last updated 2026-09-28.

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.

Sit-ups