Ultrarunning tests the outer boundaries of human endurance, but doctors say it’s still safe

About 97 runners recently braved the Badwater Ultramarathon in California. "Ultra" is the right word: It's five times longer than a marathon, forces runners to climb 17,000 feet and takes place over two days. In Death Valley. In the summer.

Can you imagine running for two days straight? Are these folks superhuman?

Tamara Hew-Butler, an assistant professor of exercise science at Oakland University in Rochester, Michigan, says no. “Like anything else, to be good at it you really have to practice and you really have to train," she says. "These people put in a lot of time to be able to complete [the races] successfully.”

On the other hand, she admits ultrarunning is a tremendous strain on the heart and body and, in extreme cases, could even kill you.

Greg Whyte, a professor of applied sport and exercise science at Liverpool John Moores University, agrees that endurance running at this level is incredibly arduous. He's careful not to warn people away from endurance running, though, which does have real health benefits.

For one, he says, despite myths, "the fact is, linear endurance events, like running or swimming or cycling — those things that require repetitive action over and over again — actually are very good for the joints.” Impact sports, on the other hand, such as American football, soccer and baseball cause much more traumatic injury to joints, which can often lead to osteoarthritis.

But there are certainly dangers that would-be ultrarunners do have to watch for. One is gastrointestinal distress, which Hew-Butler says 60 to 70 percent of ultrarunners have developed at some point. There's also overconsumption of water. Most people fear dehydration, so in many cases runners are told to “drink beyond thirst” during a race — and events have started catering to this view.

“[They] started putting water stops every mile, or every half mile, so people were drinking above the body’s signal, which is thirst,” Hew-Butler says. “When we try to outsmart our bodies with how much water we think we need or how much salt we think we need, [that’s] where the problems begin.”

The most serious is a condition called hyponatremia, which is low blood sodium. When the amount of sodium in fluids outside the blood cells becomes too low, water begins to flow into the cells to balance the levels, causing the cells to swell.

In severe cases, the lungs will fill up with fluid and a runner can develop pulmonary edema. Runners can also develop brain swelling so bad that it pushes the brain stem out of the skull. 

Whyte and his colleagues have also found permanent scarring on the hearts of 6 out of 12 ultrarunners to whom they gave a Cardiac MRI. Thankfully, these more severe problems seem to be at the margins of the sport. One of the scarred runners had competed 650 marathons and 250 ultras in his lifetime. “We’re talking about the very end of the spectrum,” Whyte says. And Hew-Butler says the brain swelling problem occurs in less than one percent of the runners she's studied.

Whyte reminds people that if they have any kind of pre-existing condition, particularly anything to do with the heart, the strain of ultra-endurance distances is obviously of great concern. But, he says, “The thing to remember is the human is uniquely placed for endurance. In fact, we’re the best endurance animal on the planet, bar none.”

And, of course, ultrarunning isn't the only way to go. If all of this sounds a bit intimidating, or you are simply at a point in your life when being an ironman of any kind seems out of reach, here is something to consider: a recent study in the Journal of the American College of Cardiology suggests that just five minutes of running a day could provide the same health benefits as running 30 minutes.

That may sound like heresy in the world of Ultra fitness, but it may suit the lifestyle of most people just fine.

This story first aired as an interview on PRI's Science Friday.

About 97 runners recently braved the Badwater Ultramarathon in California. "Ultra" is the right word: It's five times longer than a marathon, forces runners to climb 17,000 feet and takes place over two days. In Death Valley. In the summer.

Can you imagine running for two days straight? Are these folks superhuman?

Tamara Hew-Butler, an assistant professor of exercise science at Oakland University in Rochester, Michigan, says no. “Like anything else, to be good at it you really have to practice and you really have to train," she says. "These people put in a lot of time to be able to complete [the races] successfully.”

On the other hand, she admits ultrarunning is a tremendous strain on the heart and body and, in extreme cases, could even kill you.

Greg Whyte, a professor of applied sport and exercise science at Liverpool John Moores University, agrees that endurance running at this level is incredibly arduous. He's careful not to warn people away from endurance running, though, which does have real health benefits.

For one, he says, despite myths, "the fact is, linear endurance events, like running or swimming or cycling — those things that require repetitive action over and over again — actually are very good for the joints.” Impact sports, on the other hand, such as American football, soccer and baseball cause much more traumatic injury to joints, which can often lead to osteoarthritis.

But there are certainly dangers that would-be ultrarunners do have to watch for. One is gastrointestinal distress, which Hew-Butler says 60 to 70 percent of ultrarunners have developed at some point. There's also overconsumption of water. Most people fear dehydration, so in many cases runners are told to “drink beyond thirst” during a race — and events have started catering to this view.

“[They] started putting water stops every mile, or every half mile, so people were drinking above the body’s signal, which is thirst,” Hew-Butler says. “When we try to outsmart our bodies with how much water we think we need or how much salt we think we need, [that’s] where the problems begin.”

The most serious is a condition called hyponatremia, which is low blood sodium. When the amount of sodium in fluids outside the blood cells becomes too low, water begins to flow into the cells to balance the levels, causing the cells to swell.

In severe cases, the lungs will fill up with fluid and a runner can develop pulmonary edema. Runners can also develop brain swelling so bad that it pushes the brain stem out of the skull. 

Whyte and his colleagues have also found permanent scarring on the hearts of 6 out of 12 ultrarunners to whom they gave a Cardiac MRI. Thankfully, these more severe problems seem to be at the margins of the sport. One of the scarred runners had competed 650 marathons and 250 ultras in his lifetime. “We’re talking about the very end of the spectrum,” Whyte says. And Hew-Butler says the brain swelling problem occurs in less than one percent of the runners she's studied.

Whyte reminds people that if they have any kind of pre-existing condition, particularly anything to do with the heart, the strain of ultra-endurance distances is obviously of great concern. But, he says, “The thing to remember is the human is uniquely placed for endurance. In fact, we’re the best endurance animal on the planet, bar none.”

And, of course, ultrarunning isn't the only way to go. If all of this sounds a bit intimidating, or you are simply at a point in your life when being an ironman of any kind seems out of reach, here is something to consider: a recent study in the Journal of the American College of Cardiology suggests that just five minutes of running a day could provide the same health benefits as running 30 minutes.

That may sound like heresy in the world of Ultra fitness, but it may suit the lifestyle of most people just fine.

This story first aired as an interview on PRI's Science Friday.