In the first presidential election rematch in 68 years, there was very little new that could be gleaned about Donald Trump and Joe Biden from what they said during Thursday’s debate – making body language all the more important, experts told The Post.

From the outset, the occasion felt too big for Biden, 81, who rigidly shuffled to his podium before Trump, 78, took the stage.

“A lot of body movement, in [terms of] body language, is hard for him to change, unless he really committed to intense weightlifting or muscle training,” said body language expert and Carnegie Mellon drama professor Miso Wei. “Otherwise, a lot of stiffness and the slow pace is really caused by his age.”

Though Biden is just three years and seven months older than Trump, he appeared far more decrepit and elderly than his predecessor, Wei added.

“The way he speaks, there’s no way to hide his age,” she said. “And the way he is currently – the shape his body currently is in – there’s just no way to hide his age.”

Biden’s voice was weak and breathy, causing him to sound as elderly as he looked. He also seemed “out of breath” during the debate, according to Wei– which the White House attributed to a cold.

“I would encourage him to address his old age and then tell us, ‘OK, I’m old, but here are the advantages of my age: I can provide wisdom, I provide experience,’ instead of [trying to] hide from it,” she said.

Trump, on the other hand, presented his points in a robust voice, coming across as more authoritative based on sound and stature alone, brain and body language expert and psychiatrist Carole Lieberman told The Post.

“I feel happy, you know, buoyed by the way that [Trump] did,” said Lieberman, who plans to vote for the 45th president this November.

Still, she said that Trump “wasn’t perfect.”

Just as Biden did nothing to shake off criticisms of his advanced age, Lieberman said Trump could have done more to refute accusations that he is self-absorbed.

“I thought he did a little too much, ‘I was the greatest this and I was the greatest that,’ but, I mean, I kind of understand,” she said. “… But he should have done a little less of that, because that’s kind of a turn-off.”

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“People say he’s narcissistic, so you don’t really want to play into that,” Lieberman added.

Biden, who won points in his prior face-offs against Trump in 2020 for seeming “empathetic” to struggling Americans at the height of the COVID-19 pandemic, failed to deliver that impression Thursday night, according to the psychiatrist.

“Biden didn’t seem to be aware of how much pain Americans are in. He was just trying to say, ‘Oh, we’re doing great, blah, blah, blah,’ but people are really suffering in so many different ways,” she said. “He didn’t even admit that there was a problem.”

Though the incumbent failed to exude empathy, Lieberman said Biden did provoke empathy – just not in the way most presidential campaigns would want.

“Though I am certainly a Trumper, but you couldn’t help but feel sorry for Biden,” she said. “It was like your grandfather, you know, he was getting lost in one sentence after another and you had to feel sorry for him, in a way.”

Even when the candidates weren’t speaking, there was much to glean from the debate stage. For example, Wei said that next time, she would caution Trump against smirking while Biden is speaking because it “sends out a condescending tone.”

However, she added, Biden frequently came across as lost while his rival was responding to the moderators.

“I would encourage [Biden] to pay attention to the moments when he’s not talking,” she said, “because when he’s not talking, his facial expression opens [and he] zones out with wide-open eyes.”