I applaud both the athlete and the research so please forgive this ignorant question. Even if he can handle the waves, isn't he at a huge risk of being eaten by a shark or other predator as he does a 6 month swim across the Pacific?

According to Wikipedia, during his Atlantic crossing "he was accompanied by a 40 ft. sailboat that had an electromagnetic field for 25 feet to ward off sharks. He was followed by a great white shark for 5 days."

Any idea how that works?

Sharks don't have internet access to know where he is, and fishermen have to go to quite a bit of effort to find their catch. Very few people are eaten by sharks, his odds of not being eaten are excellent.

His flesh eating enemies are likely to be microscopic. I would worry about things like contact dermatitis and skin infections from swimming thru who knows what.

This ignores the fact that your odds of being eaten by a shark may be significantly higher in the open ocean than at the beach. See https://en.m.wikipedia.org/wiki/Oceanic_whitetip_shark

At the risk of sounding naive, isn't "dangerous for your health" implied by "extreme"? The human body seems to be evolutionary geared towards moderate intensity with regular frequency more than anything else.

That is exactly what they're trying to find out. From the article:

"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."

It could go on to show that extreme (exercising at low intensity for 8 hours a day for 5-6 months) isn't "dangerous for your health".

"It could go on to show that extreme (exercising at low intensity for 8 hours a day for 5-6 months)"

That doesn't sound extreme by any definition. It sounds really hard and is a lot of output over time, but it is not at all what I would characterize as "extreme".

If I were trying to discover what "extreme" exercise did to ones heart (or body, whatever) I would simulate a life or death scare that would enlist adrenaline and then present an insurmountable obstacle (basically a steep hill, or staircase that doesn't end) and have them run to muscle failure.

That sounds like extreme physical output and that would be an interesting scenario to test heart health in.d

8 hours of exercise each day is an extreme. A sudden start (like you describe) is also an extreme. The latter is easy to measure and test in a lab (sort of), the former isn't really. It'd be hard to find the funding to pay people to perform that level of physical activity day after day (constant motion, not the start on stop of most pro athlete training schedules), for months at a time.

Surely you can easily find people in poor agricultural countries that do manual labour in fields for many hours everyday. How about women in paddy fields, bent over tending the rice plants for several hours each day?

I wonder if going through special forces selection processes, which often include extreme endurance and nasty resistance to interrogation training, have any long term health impact?

Ah OK, my bad. In the end, it all comes down to "Damn, the human body is a fantastic machine".

Does it count if he is using a snorkel? I know that's like the world's dumbest question, but I am really tempted to use a snorkel at my local swimming pool to help get exercise and avoid the whole not breathing for half the time issue.

If he can, so can I :-)

You're doing it wrong if you're not breathing half the time. You just inhale sharply and exhale slowly for a few strokes; it should be almost meditative.

At my local pool there's a 60+ year old who swims daily with a snorkel. He's a pretty good swimmer, does about 4,000 meters every day.

Go nuts...

http://www.finisinc.com/swimmers-snorkel.html

    > how his heart holds up for eight hours of freestyle
    > every single day

I expect NPR to not confuse freestyle and front crawl :-/

I think NPR is correct since freestyle means any stroke. Do you really think he's just going to do front crawl for 5-6 months, 8 hours a day? I'm sure he'll do some breaststroke and backstroke as well.

Generally, at least in competitive swimming, "freestyle" is synonymous with "front crawl." Technically, you can swim using any stroke you want during a freestyle event, but hardly anybody does since the front crawl is both the fastest and most efficient.

I would go even further to say that after years of competitive swimming, I literally never heard it called "front crawl" by anyone. Every coach, swimmer, heat sheet, swimming record, etc...says freestyle.

NPR calling freestyle "front crawl" would be like referring to Tuberculosis research as "the consumption."

Except that for pretty much everyone, especially everyone involved with swimming, they are synonymous.