Crunches: How to do them and 3 crunch variations for the best ab workouts

Muscular man doing twist abs exercise with raised legs. Photo of young man workout along outdoor in the city
(Image credit: Shutterstock/ Romariolen)

If you’re wondering whether or not to add crunches to your abs routine, we'll let you know their benefits and drawbacks, and give you three crunch variations to try.

Strong core muscles don’t just look good — they do a whole lot more for your body. These muscles consist of superficial and deep muscles that wrap around your torso and extend to your hips and glutes. As a network, your core muscles support good posture, protect your lower back and help you lift heavier and move more efficiently, with less chance of injury. 

But yes, defined abs do pop as well. Below, we cover how to do “traditional” crunches and why these three crunch variations are worth the hype alongside the best ab exercises around. 

How to do crunches

an illo of a man doing a crunch

(Image credit: Shutterstock)

Here’s how:

  • Start on your back with both hands resting on the back of your head
  • Bend your knees and place both feet on your mat, hip-width apart
  • Engage your stomach muscles, then lift your upper back off the mat while keeping the lower back pressed into the mat
  • Pause, then slowly lower back to your starting position.

Crunches: Benefits

When deciding on ab workouts, consider weighing up the pros and cons of sit-ups vs crunches

Like many of the best ab exercises, including sit-ups, crunches develop a stronger core, which improves posture, mobility and flexibility and helps you function better day-to-day. For many people, crunches are accessible, but if you’re working with a back injury, we recommend checking in with a personal trainer or doctor first. 

You could argue crunch variations offer more variety than sit-ups, but there are now so many ways to modify the moves that it’s pretty hard to call it. The benefits of crunches will vary depending on the exercise — some target the oblique muscles using lateral flexion and twisting, and others primarily hit the rectus abdominal muscles (think the six-pack look), which account for movement between your pelvis and the ribcage. 

But if visible abs are the goal, you’ll need to look at other lifestyle factors like body fat percentage and diet. Here are 5 reasons you can’t see your abs yet despite working out.  

Crunches: Common mistakes

Regardless of the crunch variations you try, the movement often involves driving your head closer to your legs or vice versa (or both!) A common mistake is hyper-flexing the neck, so keep your neck in a neutral position rather than tucking your chin to your chest. 

Try to keep your lower back pressed into the floor at all times, and during standing crunches, keep a neutral spine, proud chest and flat back. 

Regardless of how good your form might be, the core exercise could be off the table for some people. If you have a neck injury, are pregnant or have just had a baby, focus primarily on working your pelvic floor and deeper core muscles first, rebuilding strength before progressing to crunches.

Your abs are responsible for stability and anti-rotation, so for beginners, practicing isometric ab exercises like planks, and ab exercises for the deeper core muscles, like leg raises, should be a priority to build foundational core strength. 

We also recommend learning the most important thing to do when working your abs so that you can understand how core exercises should feel before trying advanced ab exercises.

3 crunch variations to add to your ab workouts

1. Sumo squat side crunch

Get more bang for your buck by working your legs, shoulders and obliques. Adopt a wide stance with toes pointed out (here’s how to do a sumo squat in more detail), and lower into a squat with thighs parallel to the floor. Bend your elbows and raise your arms to shoulder height with palms facing forward, or place them behind your head and draw your shoulder blades together. Engage your core and keep your hips square, then drive your left elbow to your left knee and return to the starting position. Repeat on your right side. 

To add an extra challenge, hold a pair of dumbbells throughout. Avoid rounding your back or leaning forward.

2. Standing overhead side bend

Strengthen your obliques, shoulders and back muscles with side bends. To do the move, stand with your feet hip-width apart, engage your core and keep a tall spine. Hold a weight in both hands and extend your arms overhead, pressing your hands against the weight. With control, bend to the left on an exhale, keeping your hips facing forward and chest lifted. Pause, then inhale as you return to the center and exhale as you move to the right.  

3. Frog crunch

This crunch activates the abs, obliques, hips, quads and adductor muscles along the inner thighs. Start on your back with your hands behind your head and legs extended away from you. Bring the soles of your feet together and allow the knees to fall outwards. On an exhale, lift your upper back off the mat and bend your knees, drawing the elbows and thighs toward each other. With control, slowly lower back to the starting position. 

More from Tom's Guide

If crunches are off the table for you, we say forget them! Here are several ways you can forget crunches and upskill your ab workouts without them.

Sam Hopes
Senior Staff Writer - Fitness

Sam Hopes is a level III fitness trainer, level II reiki practitioner, and senior fitness writer at Future PLC, the publisher of Tom's Guide. She is also about to undertake her Yoga For Athletes training course. Having trained to work with mind and body, Sam is a big advocate of using mindfulness techniques in sport and fitness, and their impact on performance. She’s also passionate about the fundamentals of training and building sustainable training methods.  When she's not writing up her experiences with the latest fitness tech and workouts, you’ll find her writing about nutrition, sleep, recovery, and wellness.