Jimmy Carter’s Secret to Living to 99, According to His Grandson

As Jimmy Carter, America’s longest-living president, turns 99 on Oct. 1, his grandson shares what he believes is the secret to his grandfather’s long life: exercise.

“If he got to a new city that he had never been to before, whether there was Secret Service or not, he would say, ‘Hey, is there a bike?’” Jason Carter, a lawyer and former Georgia state senator, told TIME in a video chat on Sept. 28. He says his grandfather would always make time to jog around places he visited, and when he couldn’t jog anymore as he got older, he switched to riding a bike. Jimmy Carter also used to play tennis every day. “Stay active,” Jason says.

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Jason jokes that the one sport that the 39th U.S. President and Nobel Peace Prize winner didn’t excel at was fishing, recalling a time when they were fishing for grouper and his grandfather couldn’t catch any fish. He made his grandson switch sides with him on the boat to see if that would change his luck.

But while Jason Carter attributes his grandfather’s longevity to an active lifestyle, he believes Jimmy Carter might have a different answer. Jason thinks that his grandfather would say that the secret to his long life is his wife of 77 years, Rosalynn Carter. In 2015, the former President said, “The best thing I ever did was marry Rosalynn. That’s the pinnacle of my life.”

The two answers are perhaps related. Rosalynn was Jimmy’s main jogging partner. TIME described how the couple would make time to pound the pavement during his presidency in the April 23, 1979, issue of the magazine:

The presidential couple, in jogging attire, set out together on a course around the White House South Lawn (measured one memorable afternoon at a quarter-mile by panting correspondents who trailed Lyndon Johnson for 18 laps on an improbable mobile press conference). The Johnson quarter-mile is not the only Carter family run. They couple-jogged in Cairo and Jerusalem on recent visits abroad. Last week at Camp David, Rosalynn reached a running high. Trailed by two carloads of agents togged out in double-barreled shotguns, the First Lady panted a full 4 1/2 miles. “This is the farthest Rosalynn has ever gone,” announced her proud husband, adding, “On good days, I like to go ten.”

The former Commander in Chief is much more physically limited after a serious fall in 2019. He’s been in hospice care since February, but will take time to celebrate his birthday in a small family event at his home in Plains, Georgia, according to Jason. (The date of some birthday-related festivities at his library in Atlanta, Georgia, got moved up from Oct. 1 because of a looming government shutdown.)

Reflecting on his grandfather’s legacy, Jason calls it a “millennial presidency,” given all of the issues his grandfather tackled that are top of mind for the millennial generation. He says: “If we had listened to his presidency when they started talking about climate change, when they started talking about changing the way that we consume energy, solar and alternative sources—we would be far far ahead of where we are now. In those ways—on the environment, social justice, human rights—the presidency itself was way ahead of its time.”