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 was getting his first physical as president at Walter Reed National Military Medical Center in Bethesda, Maryland.

It comes the day before he turns 79.

Biden waved to reporters as he arrived at the hospital.

Shortly before, 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 noontime, 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.”

She said the White House would publicly release a written summary of the president’s physical Friday afternoon.

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 Dr. Kevin O’Connor as his White House physician shortly after taking office.

O’Connor has served as Biden’s primary care physician since 2009, when he was appointed physician to the then-vice president. 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.