Jessica Biel breaks a sweat with these wild single-leg skater squats—and now so do I

If you’re looking for fitness inspiration, there’s one woman who always comes through. Jessica Biel is basically the Hulk in chic activewear, celebrating good news with aerial flips and preparing for award shows with a round of pistol squats. And now she’s back with another ridiculously tough exercise called skater squats.

In a recent Instagram video, the Biel showcases the move during a session with her trainer, Ben Bruno. And she doesn’t just stick with the basics. Biel ups the ante with long holds as she lowers her leg to the floor. “Wanna see something crazy? Jessica Biel does skater squats with 8-second eccentrics for sets of 6 reps. This is just nuts,” he wrote. “This isn’t something we did one time for the video either—this was her third set, and I have her do these routinely. It’s really a wonder she hasn’t fired me yet.”

Biel’s sweat-inducing skater squats are meant to turn pain into gains. “By focusing on one side of the body, you’re able to improve balance, build stability, and override muscular compensation in the glutes and quads while getting an amazing calorie torch,” says Chicago-based celebrity personal trainer Gideon Akande. And when you add the dumbbells and holds into the mix, you get even more out of the movement.

“Eccentrics—the eight-second lowering phase—are a really great way to create more force with less energy, build more strength, and make this more attainable without having to use really heavy weight,” says Nike master trainer Betina Gozo. “When you slow a movement down and focus on the eccentric, it also gives you an opportunity to be aware of all the correct muscles you should be using, whereas when you’re speeding up movements or just moving through the motion, it’s easy to overcompensate to get through the movements.”

How to perform skater squats like Jessica Biel, according to trainers

If you want to work up to Biel’s intensity, listen to Akande:

1. Start by sitting on a flat surface (like a chair, ledge, or stair landing) and perfecting your squat. When you feel strong with both feet down, perfect the same movement on one leg.

2. To take things to the next level, remove the flat surface and hold onto a chair or the wall (or use a suspension trainer, like a TRX) or to support your balance as you continue to build strength with this single-leg movement.

3. Whether you’re ready for Jessica’s variation or continuing to build on any of the above, three sets of 8 to 10 reps on each side will progress you to your next level.

If you’re ready to go all in right away, listen to Gozo:

1. Standing on one leg, hover your back leg off the ground behind you. Bend your knee to start bringing your butt back.

2. Get as low as you can to start, while still being able to stand back up. The focus will be driving through the heel you’re standing on and keeping your core engaged, parallel to your shins, and not being completely keeled over.

3. You eventually want to be able to tap your back knee to the ground and stand back up.

Note: You can also add small dumbbells into the mix, holding them straight out in front of you as you lower to the floor (as seen in the video above).

Want more inspiration from Jessica Biel? Check out her wellness résumé. And find out which hip openers she uses to combat tightness.