It’s no revelation that Michelle Obama works out—her toned arms prove it, but exactly what is her workout routine and secret to keeping svelte?

Spies at The Washington Post spotted the First Lady at Washington, D.C. hotspot, Solidcore, on Sunday—the third time since February, the newspaper noted. The tipster said two “burly men” who were likely Secret Service security guards were standing outside of the entrance of the gym.

Obama was also spotted inside the gym doing “some sort of bicep curls,” showing off her famously-toned arms.

Back in January, Obama told Ryan Seacrest during his radio show that she works out for an hour and a half every day, with 45 minutes of cardio, as reported by The Washington Post. But so far, her exact workout routine and details of her fitness regimen have been concealed.

Solidcore’s owner, Anna Mahlum, would not comment to The Post about Obama’s workout regimen because of coach-client privilege, but said the retention rate at the gym is “over 75 percent.”

“There’s no preferred treatment,” Mahlum told the newspaper. “That’s why people keep coming back. There’s this equalizer in the workout. This is a place where you come to work — a place where you’re honest with yourself and your capabilities.”

So happens during a 50-minute Solidcore class?

According to its owner, it’s intense.

“You’re working muscles to the point of failure,” she said in February.  “No matter who you are, you can’t make it through without taking breaks.”

For $35 (or $25 during off-peak hours), the workout is based off of the “The Lagree Fitness Method,” which began in Los Angeles in 2001. The method is high-energy and done on a MegaFormer, which is a fusion of a Pilates reformer and a total body gym. The site said Lagree Fitness “uses slow and conrolled full-body movements with constant tension to work your muscle fibers to failure, forcing them to rebuild a more sculpted, stronger and solid you.”

At Solidcore, moments are done in compound, meaning working out multiple muscles at the same time in two-minute intervals, and cover the entire range of motion of the body. According to the website, the workout boasts an average of 600 calories burned per 50-minute class.

“After class, you will want to slap us, but then you'll want to hug us....with your toned arms and tight abs,” the site said.

Looks like the First Lady works out a bit harder than President Obama and his tiny dumbbells.