Jessica Biel is known for taking leg day to the next level. Case in point: That time she did plyo box pistol squats with dumbbells and made it look effortless AF.

But in case you had any doubts about her insane lower-body strength, her trainer, Ben Bruno, just shared a video of Biel killing one of the most intense leg moves we've seen on the 'gram.

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"Wanna see something crazy?" Bruno wrote alongside the video of Biel, who was sporting an adorable mesh crop top (Buy It; $65) and matching leggings (Buy It; $95) from her collection with Gaiam.

As if skater squats with dumbbell arm raises aren't hard enough, Bruno shared that Biel had to slowly lower her body into the single-leg squat position, over a whopping eight seconds, to complete a single rep. She did a total of six reps on each side to complete the set.

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ICYDK, this type of eccentric lowering—in which your muscles are lengthening rather than contracting—is what's most likely to make you sore during a workout. And Biel was definitely feeling the burn.

"Never has anyone in the history of the world counted slower than my trainer @benbrunotraining," she wrote when sharing the video to her own Instagram.

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This combination of movements looks like the ultimate test of strength, balance, and coordination, which is why it comes as no surprise that this wasn't Biel's first time attempting the exercise. "This isn't something we did one time for the video either; this was her third set and I have her do these routinely," Bruno shared. (Here's why mastering the single-leg squat should be your next fitness goal.)

Given how brutal the workout looks, the trainer added that he wasn't quite sure why Biel hasn't fired him yet. To that, she jokingly commented, "You're fired."

In all seriousness, though, the results of mastering these tough movements certainly speak for themselves. The 37-year-old actress and mother of one looks strong as hell. Keep it up, girl!

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This article originally appeared on Shape.com