Crossfit star Sara Sigmundsdottir swears by 2 exercises for strong and toned abs

• Sara Sigmundsdottir is an Icelandic CrossFit athlete and one of the sport's biggest stars.
• Training her core is key, and she works her abs at the end of every session, she told Insider.
• Sigmundsdottir said hollow rocks and L-sits help sculpt and tone her core.

CrossFit star Sara Sigmundsdottir is one of the fittest women in the world, training for hours every day.

The Icelandic athlete finished third at the CrossFit Games in both 2015 and 2016, but has been plagued by injuries since.

After an ACL injury made her pull out of the 2021 Games, Sigmundsdottir, 28, told Insider her recovery is going "almost too well," but she's careful not to push herself too hard before her body is ready.

Maintaining a strong core is and has always been a key part of Sigmundsdottir's training, she said, and she ends every session by working her abs.

Hollow rocks are Sigmundsdottir's 'worst enemy'

Sigmundsdottir said she's "so bad at planks," but hollow rocks are her "worst enemy." Despite being incredibly fit and strong, she finds the movement "so hard."

To perform a hollow rock, you begin in a hollow hold position. This is where you lie on your back on the floor, press your lower back to the ground, and engage your core.

Extend your arms over your head alongside your ears, lift both your upper body and your feet and legs, and think about creating a banana shape with your body. This is called the supine position. You then rock backwards and forwards, maintaining tension throughout the body.

Sigmundsdottir said 20 seconds of L-sits works her core

The other core movement Sigmundsdottir finds most challenging is L-sits using parallettes (also known as dip bars).

L-sits work the whole body. To do the exercise, hold on to the bars, keep your arms straight, and lift your legs up so they're parallel with the floor and your body is in an L-shape.

Keep your back straight, your shoulders down, your neck neutral, and maintain tension throughout the whole body. Hold for as long as you can maintain good form.

"I close my eyes and think I must have done 20 seconds, but it's only two," Sigmundsdottir said.