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Good Question: How Far Can We Push Our Bodies?

MINNEAPOLIS (WCCO) -- On Monday afternoon, 64-year-old Diana Nyad finally accomplished something she'd attempted five times over the past 35 years: swim without a shark cage from Cuba to Florida.

"We should never, ever give up," Nyad said moments after she stepped onto shore.

Nyad's lips were swollen, which slurred her speech, but she made the 110-mile swim in 53 hours. Her crew said it was the longest ocean swim ever without a shark cage or flippers. She risked hypothermia, dehydration, exhaustion and jellyfish along the way.

So, that had us wondering: How far can we push our bodies?

"I don't think we know yet what the human body can do, but the human body never ceases to surprise me," Dr. Mark Blegen, a physiology professor at St. Catherine University, said.

Blegen says the difference between someone like Diana Nyad -- or ultra-marathoner Dean Karnazes, who ran 350 miles in just under 81 hours – and normal people isn't just training, teamwork or physical gifts, it's also psychological.

"It's really that space between the ears that separates them from the rest of us," he said.

At minimum, our bodies need energy and rest.

In 1965, a high school student broke the record for no sleep: 11 days. According to the sleep expert who observed him, the 17-year-old hallucinated.

For Karnazes, after 300 miles, she was weaving into traffic. During her swim, Nyad cancelled her overnight feeding stops just to stay warm. With all of these cases, strange things happened in their bodies.

"Her heart rate probably accelerated, lack of energy, so some things were going on at the musculoskeletal level," Blegen said. "Dehydration, which affects a lot of things body temperature, brain and the central nervous system."

The hope is that your body recognizes it's going to shut down and you stop or pass out -- before you die.

Blegen says he expects many of these records to fall as experts learn more about nutrition, rest and mental toughness. We haven't yet figured out just how far the toughest among us can go.

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