Can Extreme Exercise Hurt Your Heart? Swimming the Pacific to Find Out

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?

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.

Does it count if he is using a snorkel? I know that&#x27;s like the world&#x27;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.<p>If he can, so can I :-)

<p><pre><code> &gt; how his heart holds up for eight hours of freestyle &gt; every single day </code></pre> I expect NPR to not confuse freestyle and front crawl :-&#x2F;