(CNN) When Donald Trump heads to Walter Reed's medical hospital Friday afternoon for his annual physical, he will bring with him a very interesting -- and still undercovered -- theory of exercise and energy.

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In a terrific piece on Trump's physical health , CNN's Jeremy Diamond and Kevin Liptak give us a hint of it (bolding is mine):

"Nearly a dozen White House officials and sources close to Trump said they don't believe he's set foot in the fitness room in the White House residence, maintaining his view that exercise would be a waste of the energy he has always touted as one of his best attributes."

For the uninitiated: Trump ascribes to what has been described as the "battery" theory of, um, life force. Evan Osnos, in a profile of Trump in the New Yorker a few years back , described it thusly: "Other than golf, he considers exercise misguided, arguing that a person, like a battery, is born with a finite amount of energy."

Exercise, other than golf, of course, is viewed by Trump as an unnecessary drawing down of your battery life.

This, from the book " Trump Revealed " by Washington Post reporters Michael Kranish and Marc Fisher, explains Trump's theory in a bit more detail:

"After college, after Trump mostly gave up his personal athletic interests, he came to view time spent playing sports as time wasted. Trump believed the human body was like a battery, with a finite amount of energy, which exercise only depleted. So he didn't work out. When he learned that John O'Donnell, one of his top casino executives, was training for an Ironman triathlon, he admonished him, 'You are going to die young because of this.'"

"Trump said he was not following any special diet or exercise regimen for the campaign. 'All my friends who work out all the time, they're going for knee replacements, hip replacements -- they're a disaster,' he said. He exerts himself fully by standing in front of an audience for an hour, as he just did. 'That's exercise.'"

During the 2016 campaign, Trump released scant details about his medical history. His longtime personal doctor, Harold Bornstein, released a letter in December 2015 proclaiming that : "If elected, Mr. Trump, I can state unequivocally, will be the healthiest individual ever elected to the presidency." (At 70, Trump was the oldest president ever elected to a first term.)

Since he was elected president, Trump has had a single physical -- administered by Ronny Jackson, who was the White House physician at the time -- in January 2018. At that time, Jackson pronounced Trump in excellent overall health. He later added Trump was in "very, very good health" and insisted that "I have absolutely no concerns about his cognitive ability." Asked how Trump, who disdains exercise and delights in fast food, could be such the picture of health, Jackson responded: "He has incredible genes, I just assume."

(Based at least in part on that performance before the press, Jackson was nominated to be the secretary of the Department of Veterans Affairs. He withdrew his nomination in April 2018 after a series of reports regarding his drinking habits and allegations that he had doled out prescription drugs willy-nilly - allegations he has denied. Earlier this week, Trump nominated Jackson for a military promotion .)

While Jackson issued a largely glowing report in Trump's health, he did say that he had urged the President to get more exercise. Soon after Jackson's press conference, Trump sat down for an interview with Reuters and was asked about his physical fitness.

"I get exercise. I mean I walk, I this, I that," Trump said. "I run over to a building next door. I get more exercise than people think."

Ahem.

That dearth of exercise has apparently continued. "The President received a diet and exercise plan last year after his annual physical, but the President admits he has not followed it religiously," Hogan Gidley, the principal deputy White House press secretary, told CNN on Thursday

None of this should be surprising. It's not that Trump, like most of us, wishes he could make more time for exercise but struggles to fit it into his very busy schedule. It's that he believes exercise is actually a negative thing, draining your life battery for no real point. Which is, um, not borne out by, well, doctors

In short: No matter what advice the doctors give Trump after his physical Friday, don't expect him on a treadmill anytime soon. Or ever.