If you’re tired of trying to crunch your way to a solid core or shredded midsection, there’s another foundational bodyweight ab exercise that should be in your workout routine: leg lifts.

Lifting your legs off the ground from a supine position targets the lower abs and gives you another tool to achieve that six-pack.

Here’s how to perform leg raises and its variations with proper form.

Leg Lift: Step-by-Step Instructions

• Lie on your back with your legs straight, neck raised (or relaxed on the floor), and arms at your sides or under your glutes for low back support.
• Engage your core and press your back into the floor. Keeping your legs straight and together, slowly raise them until they are perpendicular to the ground.
• Pause, then slowly lower your legs until they’re about an inch or two above the floor, keeping them straight and your core engaged.

How to Make Leg Lifts Easier

Lift and lower one leg at a time, or bend your knees as you raise your legs.

In this variation, you’ll end up with your lower legs parallel to the ground and your knees over your hips.

You can also place your arms out straight at your sides on the floor (so your body forms a “T” shape) for more support.

How to Make Leg Lifts Harder

Perform the leg raise in a captain’s chair (what some call a leg lift machine) or while hanging from a bar, lifting your legs until they are parallel to the ground.

“The hanging aspect of the leg lifts adds grip strength, thus increasing the difficulty of the move,” explains Alexa Cohen, personal trainer at Crunch Union Square in New York City.

Leg Lift Variations

These variations of the traditional leg lift add an extra challenge or change your angle of attack to emphasize different muscles.

1. Stability ball leg lift

In addition to adding some extra weight, this presents the challenge of squeezing the ball with your leg muscles, ensuring you don’t drop it.

2. Side leg lift

• Lie on your left side with your feet and hips stacked, your legs straight, and your head resting on your left arm. This is the starting position.
• Keeping your core engaged, slowly lift your right leg as high as you can without rotating your hips.
• Pause, and then lower your right leg back to the starting position.
• Complete all of your reps, switch sides, and repeat.

3. Alternating leg raise (scissors)

• Lie on your back, draw your knees in toward your chest, and wrap your arms around your legs.
• Lift your head, neck, and shoulders off the ground. Place your hands behind your neck and extend your legs so that they’re perpendicular to the floor. Point your toes.
• Keeping your head and shoulders lifted, lower your right leg 45 degrees.
• Quickly switch your legs so that your right leg is perpendicular to the floor and your left leg is lowered 45 degrees.
• Continue to switch your legs for your desired number of reps.

Leg Lift Benefits

“Leg lifts build a strong core and hip flexors, while simultaneously increasing balance and stability,” Cohen explains.

The exercise targets the rectus abdominis — the “six-pack muscle” — and also works the hip flexors and obliques. “The abdominal muscles are used isometrically to stabilize the body during the motion,” Cohen says.

But it’s not just leg lifts for abs.

Your core is also your back. Since leg lifts increase core strength, Cohen adds, they also increase support for your spine and back, which may lower the risk of back injuries.