Ruth Bader Ginsburg is an 84-year-old best known for her occupation as a Supreme Court Justice. But her decisions aren’t the only thing about her that is tough. It turns out that Justice Ginsberg is also an avid workout fiend and has had the same trainer since 1999.

The benefits of exercise go far beyond just being fit, they’ve also been found to boost mental stamina. And Justice Ginsberg seems to be a prime example. "The RBG Workout: How She Stays Strong ... and You Can Too!" was written by Ginsburg's personal trainer, 52-year old Bryant Johnson. In it, Johnson reveals everything that Ginsburg does to stay fit, including full push-ups, squats, and planks.

"A very important part of my life is my personal trainer, who has been with me since 1999 and now also trains Justice (Elena) Kagan and most recently Justice (Stephen) Breyer," Ginsburg has attributed her success and longevity in her career to her workouts with Johnson, the man behind the book.

Johnson is a record manager by day for the U.S. District Court of the District and by night trains Ginsburg and other Washington luminaries. Johnson has a military background and remains an Army reservist.

For her part, Ginsburg has not only survived Johnson’s vigorous workouts, she has also survived colon and pancreatic cancer.

In the book, a cartooned Ginsberg illustrates each exercise, clad in her purple justice robes and “trusty shoes.”

And lest you think that the book is just for the elderly or you’re considering it for your grandmas, know that it’s a rough workout for any age. A self-described “young and reasonably fit” writer for Politico decided to try out the workout. After 90 minutes, he was left out of breath and red in the face, just the results you want after a workout—at any age.

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