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Remember doing situps in your sixth grade gym class? Perhaps you switched to crunches later on in an effort to strengthen and tone your belly. Now it’s time to take that crunch up a notch and learn about the double crunch.

A double crunch is an abdominal exercise that requires you to bend your knees and curl them up toward your chest while lifting and curling your upper body toward your knees. Essentially, everything meets in the middle.

If it sounds challenging, there’s a good reason for it: The double crunch is challenging. You’re combining a crunch with a reverse crunch and working your entire abdomen. But that’s what makes it effective at strengthening your abs and helping you build a stronger core.

Plus, research suggests that better core strength typically means better balance and better postural control, which is especially important as we age.

Keep reading to learn more about the benefits of the double crunch, and how to do it.

A double crunch combines the benefits of a regular crunch and a reverse crunch.

Strengthens the rectus abdominis muscle

When you do a regular crunch, you contract your abs as you lift your head, shoulders, and upper back off the ground. Your feet stay flat on the floor.

This standard type of crunch targets the rectus abdominis muscle. This is the large flat muscle in the middle of your abdomen that stretches from your pubic bone to your sternum. Doing those crunches will help strengthen that muscle.

A reverse crunch entails lifting your bent legs off the ground while keeping your head, shoulders, and upper back on the ground. It’s also working that abdominis rectus muscle, from the other end.

When you start lifting your bent legs off the ground in a double crunch, you’re working more of that muscle, from end to end. You’re really maximizing the work that your rectus abdominus is doing.

Also works your obliques and hip flexors

In addition to the rectus abdominis, double crunches work other nearby muscles, like your obliques, which run from your pelvis to your lower ribs, and your hip flexors.

Builds your core, improves balance and posture

Here’s a key reason to do exercises like double crunches: Working on your abdominal muscles can make your core stronger. It can improve your balance and your posture.

Reduce lower back pain

Research also shows that core-strengthening work can reduce lower back pain, and core training can also help you recover from injury. So, committing to some core-strengthening work and incorporating a double crunch into your workout routine can pay off for you long term.

If you’ve never done a double crunch before, picture yourself doing a regular crunch. Now add the second part. Imagine lifting your feet off the ground and pulling your bent knees toward your core at the same time. At the middle of the move, you’re curled up like a ball.

Caution: Good form is key for avoiding injury. Resist the urge to clasp your hands behind your head, like you might have done in that sixth grade gym class. Try not to jam your chin down against your chest, too. And don’t slam your feet back to the ground as you finish the movement.

If this exercise bothers your lower back, you can keep your feet on the ground and just do a standard crunch instead.

Double crunches can be a very effective way of strengthening your abdominal muscles. But they’re not suitable for everyone.

If you have back or neck pain, you might want to skip the crunches and the double crunches, as they may put extra stress on those parts of your body.

If you’re in good health and don’t have any injuries or health conditions that would prevent you from doing double crunches, you might give them a try.

If you’ve been sedentary for a while, you might start out with some regular crunches first and work your way up to double crunches. If you’re pregnant or postpartum, check with your healthcare provider before adding crunches to your workout.

Make sure to use good form to avoid injury. If you’re having trouble, don’t hesitate to ask for help. Most gyms have trainers and instructors who can assess your form and make sure you’re doing the double crunch correctly.