12th August, 20219 min read

How to do crunches: benefits, variations and tips

Medical reviewer:
Dr Ann Nainan
Dr Ann Nainan
Libby Williams
Libby Williams
Last reviewed: 12/08/2021
Medically reviewed

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What are crunches?

Crunches are classic core exercises that are great for building a strong core and defining the abdominal muscles on the front of your body (medically known as the rectus abdominis, but often called your ‘abs’).

But that’s not all they do.

Crunches also work other core muscles, including those on the sides of your trunk (obliques), and in your pelvis, lower back and hips.

There are many different variations of this popular exercise – each designed to target different areas of your abs. But to get the most from any type of crunch and avoid injuring yourself, you’ll need to know how to do it correctly and safely. Here’s all you need to know about crunches – from the pros and cons of each type, to expert recommendations on how to do the most common types properly.

Types of crunches

When it comes to crunches, there’s a huge variety of types to choose from. That’s why starting with the 4 basic types outlined below can be helpful and may feel less overwhelming. Each targets specific abdominal muscles:

  • basic crunches – target your rectus abdominis only
  • bicycle crunches – target your rectus abdominis and oblique muscles
  • reverse crunches – target your rectus abdominis, transverse abdominis (deep muscles below your abs) and obliques
  • crossover crunches – target your rectus abdominis and oblique muscles

If you’d like to try these crunch variations, here’s a step-by-step guide on how to do each correctly according to Chiara Lewis, personal trainer and founder and creator of the TotalBody Method.

How to do basic crunches

Basic crunch

“My top tip for this type of crunch is to avoid putting too much tension in your neck or yanking it toward your chest,” says Chiara. “To avoid this, rest your head on your palms and imagine you’re holding a tennis ball between your chin and the chest. Focus on lifting your chest up toward the ceiling instead of toward your legs.”

  1. Lie on your back with your feet flat on the floor, hip-width apart. Bend your knees and place your fingertips behind your ears with your elbows wide open. Take a deep breath in.
  2. Breathe out, squeeze your abs and lift your head, neck and shoulders up toward the ceiling.
  3. Breathe in and return to the starting position.
  4. Repeat 10 to 12 times for 5 rounds.

How to do bicycle crunches

Bicycle crunch

When doing bicycle crunches, you should “avoid clasping your fingertips behind your head. Also, make sure you’ve really nailed the movement before picking up the pace. Think big: focus on fully stretching your leg and keeping your elbows wide open in each rep,” says Chiara.

  1. Lie on your back with your fingertips behind your ears and your elbows wide open. Squeeze your abs and bring both legs to the tabletop position keeping them hip-width apart (your knees need to be directly over your hips and your ankles should be in line with the knees that are bent at 90 degrees).
  2. Bring your right knee towards your chest and at the same time lift your shoulder blades from the ground, twisting your torso so your left elbow taps your right knee. At the same time stretch out your left leg keeping it off the floor.
  3. Change sides, keeping your elbows wide open and squeezing your navel into your spine. That's 1 rep.
  4. Repeat 10 to 12 times for 5 rounds.

How to do reverse crunches

Reverse crunch

A useful tip for reverse crunches is to “go slow and control each step with your abs. You should also avoid rolling too far. Only your tailbone and hips should be raised from the mat in the upward phase. Stop when more of your back starts to lose contact with the floor,” says Chiara.

  1. Lie on your back with your feet flat on the floor hip-width apart. Rest your arms along the sides of your body. Tighten your abs to slowly raise both legs to the tabletop position, keeping them hip-width apart (your knees need to be directly over your hips and your ankles should be in line with the knees that are bent at 90 degrees). This is the starting position. Keep your spine in a neutral position, with a slight natural curve in your lower back. Take a deep breath in.
  2. Breathe out as you contract your abs to curl your hips and knees toward your chest – your hips should come off the mat as you curl. Your knees should stay at the same angle. Try to keep your neck and shoulders relaxed.
  3. Breathe in and slowly return to the starting position with your hips back on the mat and your knees over your hips, still bent 90 degrees.
  4. Repeat 10 to 12 times for 5 rounds.

How to do crossover crunches

Crossover crunches

“My top tip with this type of crunch is to not let your neck do the work, but try to picture a tennis ball between your chin and chest,” says Chiara. “Try to do the movement while fully engaging your abs on your way up and controlling the movement on your way down. Focus on really getting in sync with your breathing.”

  1. Lie on your back with your feet flat on the floor, hip-width apart. Bend your knees and place your fingertips behind your ears with your elbows wide open. Cross your left leg over your right to rest your left ankle on your right knee. Take a deep breath in.
  2. Breathe out as you tighten your abs and, with control, raise your upper body off the mat reaching your right elbow to the left (raised) knee. Twist your torso to your left as you squeeze your abs.
  3. Breathe in as you slowly lower your upper body back down to the mat.
  4. Repeat 10 to 12 times for 5 rounds.

The benefits of crunches

A stronger core and better posture

Like any core exercise, crunches target a number of muscles in your trunk or torso. They help to train these muscles to work together better, which can improve your balance and stability.

The muscles in your core are the ones your body relies on most during many physical activities, from sitting and walking to lifting and playing sports, so strengthening them can make daily activities and exercise feel easier. Working on your core strength can also help improve your posture when sitting and standing, which may help reduce any muscle pain you have in your back, and prevent your muscles from becoming tired as quickly.

You’ll burn some calories

It’s common to wonder how many calories crunches burn, but this is a hard question to answer. The calorie burn you can expect from doing crunches will typically depend on a number of factors, including your age, how much muscle you have, your general fitness level and how long you do the crunches for. Crunches won’t burn anywhere near as many calories as cardio exercises (like running), but like any form of exercise, crunches will burn some calories.

You don’t need any equipment

A big benefit of crunches is that you don't need any special equipment to do them – all you need is a little bit of floor space to lie on. This means that you can easily do them wherever you are – whether that’s at home, in a hotel or elsewhere.

Less back pain

Having weak core muscles can increase your risk of lower back pain and muscle injuries. Strengthening them with exercises like crunches can help prevent injury, reduce any back pain you have and speed up recovery from an existing back injury. But, if you do have a back or neck injury, speak to a doctor before trying crunches. They can check if they’re safe for you to do. It’s also worth speaking to a personal trainer to make sure you’re doing the movement correctly to prevent making an injury worse.

The downsides of crunches

They only target your core

Although crunches are great for your core muscles, they only work a small number of muscles. If you’re looking for a full-body workout, you’ll need to add other exercises to your workout routine, as well as cardio. Guidelines suggest you do at least 150 minutes of moderate-intensity exercise each week, which should include strengthening activities on at least 2 days of the week.

They can cause injury

Crunch movements flex your spine, and this puts pressure on that area. If you have an existing back injury, or if you don’t do the exercise correctly, crunches may put extra stress on your neck and spine, and this could lead to a new injury. This also means that crunches may not be a good fit for you if you’re over 65, especially if you’ve had a back or neck injury in the past. If you’re unsure, speak to a doctor and ask a personal trainer for advice before doing crunches.

When to see a doctor

Crunches aren’t safe for everyone, so don't try them without speaking to a doctor first if you have any neck or back problems. You should avoid crunches after the first trimester of pregnancy or as soon as your belly starts to ‘show’, but speak to a doctor for specific advice if you're pregnant.

Stop exercising and see a doctor as soon as possible if you hurt any part of your body while doing crunches.

Call an ambulance or go to the emergency department if you develop any of the following symptoms after doing crunches:

  • really bad back pain
  • numbness and weakness of your legs, bottom or genitals
  • problems controlling when you poo or pee

Your health questions answered

  • Do crunches burn belly fat?

    Doing crunches won’t help to burn belly fat, but may help your belly look flatter and more toned. But to see these results, you may need to lose some belly fat. You can do this by eating a healthy and balanced diet and doing a combination of cardio and strengthening exercises.

  • How many crunches should I do a day?

    If you want to include crunches in your workout routine you should do 3 to 5 sets of 10 to 12 repetitions of each type of crunch you do. Crunches don’t burn many calories so you’ll also need to do cardio and other strength exercises if you’re looking to lose weight and build muscle. Mixing up the type of crunches you do will help you target different muscles each time.

Key takeaways

  • doing crunches can help strengthen your core and improve your posture, balance and stability
  • crunches can cause injury to your neck and spine if done wrong and can make existing injuries worse
  • crunches only target your core so you’ll also need to do other strengthening exercises and cardio for an effective full-body workout
  • there are several types of crunch exercise including basic, reverse, bicycle and cross over
  • speak to a doctor before doing crunches if you have any neck or back problems, or are unsure if they’re safe for you to do

Need more tips on how to get active? Try out our 28-day in-app get fitter plan for all the latest hacks on how to work more exercise into your daily routine. Currently available on iOS only.

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