Any day now, Texas swimmer Ben Lecomte will plunge into the Pacific Ocean off a Tokyo beach towards San Francisco. He wants to become the first person to swim across the Pacific. He’s already the first person to free swim across the Atlantic Ocean. No one knows what the physical feat of swimming 5,500 miles will have on Lecomte’s heart, but cardiologists are anxious to find out. His swim offers a rare opportunity to study whether extreme athletic performance has a harmful effect on the heart.

After completing the first swim in the history across the Atlantic Ocean, the first words out of Ben Lecomte’s mouth were “Never again.”

Now, this Frenchman is jumping into the Pacific for a swim expected to take five to six months.

The Longest Swim

A map showing the projected path Ben Lecomte will swim across the Pacific. He’s calling attention to environmental problems as well as helping researchers study his heart function.

“I’m not a fast swimmer,” Lecomte said over Skype in January, laughing.

But boy is this Texas transplant dedicated.

“Swimming is a passion, so it just comes back, you cannot just push it away,” he says.

At 48-years-old, Lecomte says he’s worried about the future for his kids. He’s diving back in the ocean to focus attention on environmental problems. During The Longest Swim, he’ll collect data on the Pacific – the microbes, the trash – but also on himself. On how his heart holds up for eight hours of freestyle every single day. This data will go to a cardiologist at UT Southwestern Medical Center, Dr. Benjamin Levine.

“My question has always been how much exercise do you need to do to injure the heart?,” Levine says. “Since Ben was planning to swim across the Pacific Ocean, we thought hey, this might be a good opportunity.”

Dave Gresham/UT Southwestern Medical Center

Swimmer Ben Lecomte (right) at Dr. Levine’s lab at the Institute for Exercise and Environmental Medicine.

It sounds a bit crazy, after all we’re told more exercise is better; and generally, it is. Yet, several studies of extreme endurance athletes have called that idea into question.

Dr. Paul Thompson is another cardiologist curious about the ways hardcore exercise affects the heart.

“If you look at people who run marathons or do triathletes, one of the things that’s been noticed, is scaring or some fibrosis in their heart,” Thompson says. “Right where the two sides of the heart join each other, we call it the septum.”

Thompson is chief of cardiology at the Hartford Hospital in Connecticut. He says this scarring at the septum is worrisome, particularly for people who have an underlying genetic condition that weakens the heart muscle.

“A second area of concern,” Thompson says, “Is that it’s been shown in a couple of studies now that people who are lifelong term endurance athletes have more coronary artery calcification than you would expect for their risk factors.”

In regular people, calcification usually means a buildup of cholesterol – not something you’d expect to find in people swimming the English Channel, running the Sahara, or tackling Iron Man competitions. Thompson says there’s likely an explanation, and most of us don’t have to worry about either scaring or calcification.

Remember, the question here isn’t whether exercise is bad, it’s whether there are diminishing returns, and if there’s such a thing as too much.

“We don’t think that long-term exercise is dangerous because long term live longer than other people.” Thomson says. “But are there changes that happen in the heart? We think there are. Our point is to investigate and figure out what’s going on.”

Which brings us back to Ben Lecomte – the guy swimming the Pacific – and the tricky task of monitoring his heart from the middle of the Ocean. UT Southwestern’s Levine has a plan, and connections with NASA to help.

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“We’re doing something called remote guidance echo.”

The Longest Swim

This wooden support boat will travel alongside swimmer Ben Lecomte and be where he sleeps as well as performs echocardiograms.

Levine has used this technology to study astronauts’ hearts on the international space station. But let’s stay on earth for now. In the ocean scenario, a small portable echo machine will be on the wooden support boat traveling with swimmer Lecomte. Once a month, Lecomte will turn it on and use a satellite phone to call a laboratory at Johnson Space center.

That’s where he’ll get coached, remotely on how to use the probe to give himself an echocardiogram.

From his desk in Dallas, Levine will see images of how fast Lecomte’s heart is contracting. How quickly the blood flows in and out of the valves, and any stress where the two sides of the heart meet. His prediction?

“I think when he comes back he’ll have signs of a little inflammation or irritation right where the right and left ventricle connect, that’s what we see in some other of these elite long endurance athletes and I think that’s what we’ll see in Ben.”

So what’s the significance of a little inflammation?

“For most people it really is of no consequence,” Levine says. “I think there can be consequence though, I think people who have pulmonary hypertension, other kinds of heart disease.”

He hopes studying Lecomte’s heart will help reveal why extreme exercise changes the heart, and understand the outer-limits of human capacity.