Exactly How to Do a Correct Sit-Up for Stronger Abs

The sit-up is a classic exercise that has been a staple of core-strengthening programs for many years. In fact, the sit-up has been a component of the U.S. military's physical fitness test for over 40 years to assess muscular endurance of the abdominal muscles and hip flexors.

While it's been thought that sit-ups are bad for your back, when done correctly, they strengthen your abs and are a great core-strengthening exercise to add to your workout routine, according to certified personal trainer and nutrition coach Jonathan Jordan, CPT.

Read on to learn more about how to do a proper sit-up, muscles worked, benefits, form tips and variations.

• ‌What is a sit-up?‌ A sit-up involves lying on your back with your knees bent and lifting your torso all the way up. Unlike a crunch, in which you just lift your shoulders off the ground, you come all the way up to a sitting position when doing a sit-up.
• ‌Muscles worked during a sit-up:‌ The sit-up works both your abdominals and your lower body. The primary muscles targeted are both the upper and lower rectus abdominis. These are the muscles in the front of your abs on both sides of your center line, and they flex your spine as you roll up. You also work the oblique muscles on the sides of your abs. Your hip flexors (iliopsoas, sartorius, tensor fasciae latae and rectus femoris) are also worked during the sit-up. In addition, the tibialis anterior in the front of your lower leg acts as a stabilizing muscle to help steady you.
• ‌Who can do a sit-up?‌ People who are healthy with no pain or joint issues can usually add sit-ups to their routine, Jordan says. For some people, however, alternate abdominal exercises may be better. The flexed motion of the sit-up can put too much stress on the spine for those with previous back injuries. In addition, sit-ups tighten your hip flexors, which may contribute to back pain for some. "Anyone with poor posture — aka a forward neck and rounded shoulders — should be cautious and may not be able to do sit-ups effectively. Anyone with lower back pain, injuries, disc bulges or degeneration should consult a doctor," Jordan says. If you have pain during or after doing a sit-up, stop what you're doing and avoid this exercise in the future. "As long as you are following a balanced core program and can perform a sit-up properly and pain-free (and have the OK from your doctor to do so), it can be a fine addition to a workout," he says.

When done correctly and when used in addition to other core strengthening exercises (like planks, for instance), the sit-up has many benefits.

The sit-up strengthens your core muscles, including the rectus abdominis and oblique muscles. A strong core helps support your back to help reduce and prevent back pain, according to the Cleveland Clinic.

Anchored sit-ups, in which your feet are held down by a partner or by a strap, are not recommended because they strengthen your hip flexors more than the abdominal muscles. Make sure you're doing sit-ups correctly (as demonstrated above) to get the maximum benefits.

"A sit-up is basic core flexion [bending forward, which is one important job of the abs," Jordan says. "Everyone does a sit-up to get out of bed in the morning, so training to flex the core can be a very functional exercise which translates to better, safer core flexion in the real world."

Having a strong core, by doing exercises like sit-ups, helps promote good posture, according to the Mayo Clinic. Maintaining proper posture when sitting at your desk or standing for long periods of time helps to keep your spine in the right alignment, prevent muscle imbalances and promote a healthy, pain-free back.

To get the most out of your sit-ups, avoid these common mistakes.

Anchoring your feet down during a sit-up — either by someone holding them or using a strap — works your hip flexors more than your abs. This may result in tight muscles that can pull on your pelvis, which can cause back pain, according to the American Council on Exercise (ACE).

‌Fix it:‌ To prevent the risk of back injuries with sit-ups, avoid doing them with your feet anchored. If you have previous back injuries, you may want to avoid the sit-up in favor of other core-strengthening exercises, like planks or glute bridges, per ACE.

Your feet coming off the floor while doing sit-ups is a very common mistake. This happens because your abs aren't quite strong enough to lift you up without momentum. You may also be trying to do them too fast. Making sure your feet are in the right position also helps prevent this.

‌Fix it:‌ Move your feet further away from your butt, as keeping them too close can make a sit-up harder. You can also try slowing down your sit-up. If your abs aren't strong enough yet, you may need to work your way up to this exercise by doing the straight-leg sit-up, crunch or butterfly crunch.

"I do not recommend loading [adding weight to] a sit-up," Jordan says. "This is very commonly seen on decline benches in the gym [with people] holding a heavy weight overhead. While some people may be able to perform this without injury, I have seen many disc injuries result from this, and in my opinion, it's not worth it."

‌Fix it:‌ Stick to just using your body weight during a sit-up — or make it more difficult by doing a sit-up on a stability ball as demonstrated below.

Try to avoid using your hands as momentum to help lift your chest off of the ground, as this takes away from the core-strengthening aspect of the move. Keep your movements slow and controlled.

‌Fix it:‌ If you find it challenging to do a sit-up with your hands behind your neck, cross your arms in front of your chest and place your hands on your shoulders.

If you can't perform a basic sit-up without lifting your feet off the floor or using your hands for momentum, start with the straight-leg sit-up to strengthen your core.

The crunch involves a smaller range of motion than the sit-up, but it's a great exercise to strengthen the rectus abdominis. This is also a great exercise for those who can't do a sit-up due to a back injury.

Ready to kick it up a notch? Try doing a sit-up on a stability ball. Not only does it really work your core, but it also helps reduce pressure on your spine for those who find regular sit-ups painful.

If you're still building up to a full sit-up or have back pain or an injury that prevents you from doing the full movement, you can still target your abs, hip flexors and core with alternative exercises, according to the University of Michigan.

Jordan also recommends other core strengthening exercises such as the McGill crunch (also called modified curl-up), plank variations and the Pallof press.

Correct form is critical to getting the most benefits from any exercise and avoiding injury. If you are unsure of your form or a good progression to build up to doing a full sit-up, consider chatting with a personal trainer to help you develop a workout program that fits your needs and goals.