It was a question that plagued Joe Biden’s presidential campaign: Could a 77-year-old man — who at age 78 would be the oldest person ever to assume the presidency — handle the rigors of the job?

Candidate Biden acknowledged it was legitimate for Americans to question his fitness for office.

“The only thing I can say is watch. Watch! Check my energy level, determine whether I know what I’m talking about,” he told voters during the 2020 campaign.

Now, on Friday, nearly a year into his term, Biden has gotten his first physical as president at Walter Reed National Military Medical Center in Bethesda, Maryland.

It came the day before he turns 79.

After about five hours inside, Biden walked out giving two thumbs up.

“I’m doing great!” Biden told ABC News Correspondent Karen Travers, when asked how he was feeling. “I’ve had a great physical and a great House of Representatives vote. Good day,” Biden said, referring to House Democrats passing his “Build Back Better” plan earlier in the day.

Shortly before he arrived, the White House revealed that for some of the exam he would be under anesthesia and would briefly transfer power to Vice President Kamala Harris.

“This morning, the President will travel to Walter Reed Medical Center for a routine physical. While he is there, the President will undergo a routine colonoscopy,” press secretary Jen Psaki said in a statement.

“As was the case when President George W. Bush had the same procedure in 2002 and 2007, and following the process set out in the Constitution, President Biden will transfer power to the Vice President for the brief period of time when he is under anesthesia. The Vice President will work from her office in the West Wing during this time,” she said.

Around noon, the White House said it sent letters at 10:10 a.m. to House Speaker Nancy Pelosi and Sen. Patrick Leahy, president pro tempore of the Senate, to inform them Biden was going under sedation. The House speaker is second in line to the presidency after the vice president and the president pro tempore of the Senate is third in line under the 25th Amendment dictating the order of presidential succession.

Psaki tweeted that Biden had spoken with Harris and chief of staff Ron Klain at approximately 11:35 a.m., saying “@POTUS was in good spirits and at that time resumed his duties.”

Late Friday afternoon, the White House put out a promised detailed medical summary.

Biden is a ‘healthy, vigorous 78-year-old man,” who is “fit for duty” and “fully executes all of his responsibilities without exemptions or accommodations,” the president’s physician, Dr. Kevin O’Connor wrote.

While Biden got a mostly clean bill of health, O’Connor — who has been Biden’s doctor since 2009 — noted two specific observations: his frequent throat clearing, and a stiffened gate, compared to last year.

“The president has exhibited increasing frequency and severity of “throat clearing” and coughing during speaking engagements,” O’Connor wrote. “He has exhibited such symptoms for as long as I have known him, but they certainly seem more frequent and more pronounced over the last few months.”

O’Connor noted that Biden being president and the increased attention could be playing into the perception of the symptoms, but required further investigation. Ultimately though, O’Connor said that his initial assessment that “gastroesophageal reflux” was to blame for the cough still stands.

Of his stiffened gate, O’Connor said Biden acknowledges that he is stiff in the morning, though it improves over time. O’Connor said that after a battery of tests, general “wear and tear” of the spine was partly to blame– though no specific treatment was needed.

A new finding for Biden was a “mild peripheral neuropathy in both feet.”

“He did not demonstrative any motor weakness, but a subtle difference in heat/cold perception and great toe proprioception could be elicited,” O’Connor wrote, noting this, along with the wear and tear could contribute to the stiffened gate, and “Physical Therapy and exercise prescription will continue to focus on general flexibility and proprioceptive maintenance maneuvers.”

Biden’s regular screening colonoscopy found a 3mm benign-looking polyp was identified in the in ascending colon, and was removed without difficulty, the report said.

To date, the most recent physical and medical report was one his campaign released in December 2019: a three-page summary that declared Biden “a healthy, vigorous, 77-year-old male, who is fit to successfully execute the duties of the presidency.”

At the time, Biden was said to be under treatment for four different conditions: non-valvular atrial fibrillation — a type of irregular heart rhythm, hyperlipidemia — higher concentrations of fats or lipids in the blood, gastroesophageal reflux and seasonal allergies.

The most notable health incidents in Biden’s past were the two cranial aneurysms he suffered in 1988.

Since winning the presidency, Biden suffered a fractured foot after falling while chasing his dog Major at his Wilmington, Delaware, home last Thanksgiving. He had to wear a walking boot for the injury, and was said to be “healing as expected,” according to scans from a follow-up appointment in December.

Biden named O’Connor as his White House physician shortly after taking office.

O’Connor has served as Biden’s primary care physician and was appointed physician to the then-vice president in 2009. Biden chose him for the new role due to their long history and personal relationship, according to a White House official.

Questions about fitness for office are far from exclusive to Biden — President Donald Trump, who was the oldest president elected before Biden, also faced questions about his mental and physical fitness.

Trump faced particular scrutiny for the first physical of his administration in January 2018, which his then-White House physician, Dr. Ronny Jackson, said went “exceptionally well.”

He came under fire for his effusively rosy outlook on Trump’s health while briefing reporters afterward.

In other recent administrations, physicals have generally been conducted within a president’s first year in office.

President George W. Bush got a physical in August 2001, and was found to be “fit for duty” with “every reasonable expectation that he will remain fit for duty for the duration of his Presidency.”

President Barack Obama received his first physical in office just over a year into his presidency, in February 2010. He also was found to be in “excellent health,” although doctors told hi to stop smoking.

At her news briefing Friday, Psaki declined to detail any actions Harris took during her 85 minutes as “acting president,” but observed the moment’s historic nature.

“I will leave that to her team to characterize. I know that other people have been talking about this and a woman myself, I will note that the president, when he selected her to be his running mate, obviously knew he was making history that was long overdue in our view,” she said.

“Part of that was selecting someone who would serve by your side as your partner, but also … step in if there was a reason to,” Psaki said.

ABC News’ John Parkinson contributed to this report.