Want to get the most out of an at-home abs workout? Then don’t forget your obliques—you know, those muscles along the sides of your stomach that fire up when you do motions involving twists or a turns—which are integral to an overall strong core. To fire them up sans equipment, look to celeb trainer Erin Oprea and her super-informative Instagram for guidance

Oprea—who helps Carrie Underwood stay in tip-top shape, despite the artist’s grueling recovery from an injury that resulted in more than 40 facial stitches—recently posted a plank series that specifically targets oblique strength, which she says is just as “important as overall core strength,” Self reports. And, these moves in particular are designed to “burn out the obliques,” working them to exhaustion.

Ready to turn up the core heat? Grab a mat, and send some positive vibes to your side muscles, because they’re about to werk.

Sculpt your abs with this 4-move series from trainer Erin Oprea.

1. Side-plank twist

How many: 15 to 30 reps

2. Side-plank pulse

How many: 15 to 30 reps

3. Elbow plank with hip dips

How long: 30 seconds

4. Elbow plank with knee twists

How long: 30 seconds

This is the plank-heavy workout Ashley Olsen does on the reg. Also, here’s why holding a plank for more than 10 seconds might be pointless.