(CNN) A day after returning home from the hospital following cancer surgery in December, Justice Ruth Bader Ginsburg was back working out with her trainer, Bryant Johnson.

"Here's what she does: She shows up," Johnson said in an interview with CNN this week, his first since Ginsburg's surgery.

The routine was light, to be sure, as Ginsburg gingerly completed rotational exercises and some stretching. She could barely do a two-minute warm-up on the treadmill. Johnson doesn't minimize the fact that she was "moving slow" after what he called "massive surgery." But she was eager, he said, "to get back as quickly as possible to training."

"She's a machine," Johnson concluded.

By now Ginsburg -- who turned 86 on March 15 -- has a legion of fans. They include those who watched her, as a young lawyer, transform the law in the area of gender equality. Others praise her for her stinging dissents as the leading liberal on a Supreme Court that now leans definitively to the right.

But another set of admirers looks past her monumental achievements in the law and focuses on how she has dealt with cancer, in three separate bouts with the disease. For cancer survivors, Ginsburg's public battle has been an inspiration and she has become an unlikely fitness role model.

Twelve weeks after surgery, Ginsburg has been back on the bench for a while now, often firing the first question to advocates at the lectern. She has issued three opinions that she penned during her recovery. And, according to Johnson, earlier this week she was up to a six-minute warm-up on the treadmill.

They've been working together consistently, sometimes two to three times a week.

Monday marked "the first time we did pushups off of the knees," he said.

Did she plank?

"Of course she is planking," Johnson said.

The plank

For the uninitiated, a plank is a core-building exercise meant to increase strength. It involves assuming a pushup-like position, with forearms resting on the floor.

On Friday, a local business is planning to gather on the sidewalk in front of the Supreme Court building, get on their hands and knees, and plank in honor of Ginsburg's birthday.

"We wanted to create a celebratory protest to honor the work of Justice Ginsburg as a woman who relentlessly fought for justice over 60 years," said Michelle Howell, the director of branding for The Outrage, which describes itself as an "activist apparel company" that sells what Howell calls "merch to march in." Included in the inventory are "plank like RBG" tank tops, sweatshirts and yoga mats. After paying rent and payroll, the group donates some of its profits to progressive groups.

"How does Justice Ruth Bader Ginsburg have the energy to keep dissenting?" the organization's website asks. "She planks."

Fractured ribs

Johnson says he had trained Ginsburg the day before she fell in her office in November. After the fall, she went to the hospital and was diagnosed with fractured ribs. It was while the doctors were treating the ribs that they found what would turn out to be two cancerous nodules on her left lung.

Johnson knew about the diagnosis before most people in the country. Their routine continued a week and a half after the fall. After a few more sessions, she sat him down.

"She explained to me that there were some abnormalities ... and they were cancerous." They wanted to do surgery.

He said he had told her that they would "adjust and adapt" and would pick up whenever she was ready.

Her goal, he said, was to be strong enough for the surgery.

So the workouts, which are devoid of small talk, continued.

After the surgery, they were back at it.

After the initial post-surgery meeting, Johnson, an Army reservist who also works as a personal trainer, left town for a trip and Ginsburg continued her recuperation until they could meet again for more sessions. Johnson said the "incision" was small but the surgery had definitely "taken its toll on her."

"This is new to everybody else, it's not new to me and the justice," Johnson said. "We have been doing this together for 20 years," a long relationship that endured through her recovery from colon and pancreatic cancer. Johnson said Ginsburg was working out with him in 2014 when she felt nauseated and went to the hospital for a heart procedure.

Ginsburg declined to comment on this story.

Johnson penned a book in 2017 called "The RBG Workout: How She Stays Strong ... and You can too."

He spent more than 30 years in the Army, 12 of them as a member of a special forces airborne unit in the Reserves.

Over the last 19 years he's trained with high-level federal court officials including Ginsburg and Justices Elena Kagan and Stephen Breyer on occasion.

He says his biggest goal after Ginsburg's surgery, with the doctor's consent, was to get her moving again.

"If you have surgery, you have to start moving as soon as possible, even if it means just standing up and sitting back down," he said. "Get up and walk to the bathroom. Get up and move the body. The body is made to move. "

Johnson also works with an organization called 2unstoppable, whose mission is to encourage and support exercise among women with cancer diagnoses. The group's website, www.2unstoppable.org , connects women who have had cancer diagnoses with other women as exercise partners. It also provides oncology fitness resources including videos, articles and referrals to cancer exercise specialists.

Michelle Stravitz, a co founder of the organization, plans to attend Friday's celebration in front of the Supreme Court.

"For those women who are not accustomed to exercising or may even be afraid of it, Justice Ruth Bader Ginsburg has demonstrated that we can improve our own outcomes through exercise and we can be strong well into our 80s," Stravitz said.

The American Cancer Society says that not only is exercise safe during cancer treatment, it has been shown to help with heart and blood vessel fitness, muscle strength and body composition, according to the group's website. The goal is to stay active, and slowly increase the level of activity.

This week Johnson told the justice about the planned planking ceremony to celebrate her birthday, which drew a rare chuckle. Johnson said he had the justice hold a plank to see if she could make it through two rounds of his rendition of "Happy Birthday." She did.

Johnson says planking is not exactly Ginsburg's favorite exercise.

"You know, planks task the body and planks get respect," he said. "I think it's more that she appreciates the planks."