stomach crunch

How to do an ab crunch correctly

Posted by for Strength

Swap sit-ups for ab crunches – the perfect move for targetting abdominal muscles without putting too much pressure on your neck or lower back. 

We use our core for everything (or we at least should), which means that keeping it strong is one of the most important part of fitness. It’s not about having visibly rippling abs – it’s about stability, balance and support. A strong core keepings our body upright and functional; if those abdominal muscles are weak, it has a knock-on effect on other parts of your body such as the lower back and neck – hello chronic pain!

It’s really crucial that you concentrate on thinking about that core connection whatever workout you do, as well as in everyday life (good posture relies on relaxed shoulders and an engaged core). If you’re planning your own workout, try to factor in a ten-minute core section at the end so that you can really concentrate on small but effective movements designed to target the trunk.

One of the superstar movements of that core workout? The ab crunch. You can add weight if you want, or even extend the number of crunches you do. This is all about mind-muscle connection; minimal movement with big results. So concentrate on the muscles you feel are being worked and enjoy the burn.

Woman doing sit ups
How to do a crunch correctly


It’s all about the abs, but “the abs” are made up of four different muscles, including:

  • Rectus abdominis (runs from the rib cage to pubic bone)
  • External obliques (side and front of the abdomen)
  • Internal obliques (located underneath the external obliques)
  • Transversus abdominis (the deepest ab muscle running horizontally across the torso)


  1.  Lie on your back with knees bent and feet flat on the floor – hip-width apart
  2. Place your hands at the base of your thighs or fingers touching your temples with your elbows pointing out
  3. Engage your core and lift your upper body a few inches from the ground – sliding your hands up your thighs towards your knees (or staying on the temples). You only want to take your head, neck, shoulders and upper back off the floor – your lower back stays grounded.
  4. Come back down again, sliding the hands back down the thighs (or at the temples).

Set your timer for a minute and go for three one-minute sets with a 30-second break in between each one.

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Minimal movement

This is a targetted move so make sure it’s just the upper body that’s moving. Having your hands on your thighs can minimise potential movement in the shoulders – it’s up to you which variation you choose.

Feet flat on the floor

They shouldn’t move at all during the course of this exercise.

Keep shoulders and neck relaxed – chin up

You don’t want to yank your head off the ground. Keep everything relaxed except those ab muscles.

Mind-muscle connection

Research has shown that focusing on the muscle you’re working does increase engagement so think about those stomach muscles working as you crunch.

Side ab crunch
Try a side ab crunch to target those obliques


Weighted crunches

To make things more challenging, place a kettlebell or dumbbell behind your head on the floor. Grab it and press it over and in front of your head as you crunch up and then back over as you come back down. Be sure to keep your feet firmly planted on the floor – if they start coming up, you may want to choose a slightly lighter weight.

Side crunch

Keeping your body in the same position (feet on the ground, knees bent, back on the floor), you’re going to lift your upper body and crunch to the side rather than straight forwards. This time, place your fingers on your temples so that your arms are bent out to the sides and crunch with your right elbow aiming towards your left knee. Don’t push to touch the knee, just move towards it. Come back down and crunch up towards your opposite knee.

Lifted legs crunch

Keeping the legs glued together, lift them into the air and crunch up as usual – keeping the back firmly on the ground.

Oblique crunch

Again, lie on your back with knees bent and feet flat on the floor. Roll your knees to one side down on the floor and place your hands across your chest to reach for the opposite shoulders. Keeping knees together and legs and hips firmly on the floor, crunch up until your shoulders are three inches off the floor – hold for a few seconds and then lower back down. Go for 12 crunches on one side, then repeat on the other.


Most of us will have grown up thinking that sit-ups were the way to strengthen stomach muscles but they seem to have fallen out of favour. Why? Well, sit-ups are notorious for exacerbating aches and pains.

Harvard Medical School says that sit-ups are hard on your back because “they push your curved spine against the floor and work your hip flexors, the muscles that run from the thighs to the lumbar vertebrae in the lower back. When the hip flexors are too strong or too tight, they tug on the lower spine, which can create lower back discomfort.”

While sit-ups engage more muscles (lower back, hip flexors, and neck), you run the risk of putting stress and strain on the spine and neck; if you sit at a desk all day, you might already be tight in those areas anyway so you definitely don’t want to add to that.

Ultimately, both moves should be the icing on your fitness cake – whichever one you choose. Core exercises alone won’t strengthen that area but when they’re added on as a finisher to your cardio or strength workout, they give you a great opportunity to isolate those muscles. Good form, as always, is your best protection against injury.

(Pictures: Getty/Instagram)

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Miranda Larbi

Miranda Larbi is the editor of Strong Women and Strong Women Training Club. A qualified personal trainer and vegan runner, she can usually be found training for the next marathon, seeking out vegan treats or cycling across London on a pond-green Tokyo bike.