August 07, 2015 06:34 PM

Amanda Edwards/WireImage

Natasha Lyonne has been looking fitter than ever – and now we know why!

The Orange Is the New Black Star is a fan of YAS fitness centers, which offer classes that combine yoga and spinning. The 36-year-old has been spotted at the studio’s Portland location twice this past week.

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“She was intense in the spin class, and worked hard the entire time,” a source tells PEOPLE. “She was very into the yoga, too. She seems likes an experienced yogi.”

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Attending the class “very incognito,” Lyonne was “make-up free and under-the-radar,” says the source, who adds that she was also friendly, greeting everyone at the studio with hellos and goodbyes.

Lyonne isn’t the only celebrity fan of YAS – Renee Zellweger, Elle MacPherson, Rosario Dawson, Zooey Deschanel, Emily Deschanel, Kirsten Dunst, Alicia Silverstone, Justin Long and Kate Hudson are all regulars at the studio’s Southern California locations.

Gabrielle Olya, @GabyOlya

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