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Extreme Exercise and the Heart: An interview with Dr. Benjamin Levine

Dr. Levine is the founder and director of the Institute for Exercise and Environmental Medicine (IEEM) at Texas Health Presbyterian Dallas. IEEM is the largest center for the study of human physiology in the United States. During the swim he will function as Ben’s cardiologist, as well as a researcher on two of The Longest Swim’s eight research projects.

A current controversy in cardiology revolves around the question of whether extreme athletic performance has a harmful effect on the heart. Some researchers have suggested that training for extreme marathons can lead to cardiac fibrosis, or a stiffening of muscles in the heart. Other scientists, including Dr. Levine, instead point to data indicating that the “athlete’s heart” of endurance athletes is “big, compliant, muscular, and can pump a lot of blood very fast” to support strenuous physical activity.1

Ben’s swim across the Pacific presents a unique opportunity to further study the effects of endurance exercise on the human heart. In order to track changes to his heart muscle, Dr. Levine and his team will use remote guidance echocardiography, the same technology used to monitor astronauts on the International Space Station. Echocardiography uses high-pitched sound waves that are bounced off the heart, then echoes of these waves are picked up by a machine and translated into video imagery. Unlike a traditional echocardiogram, performed on the patient by trained individuals called sonographers, a remote guidance echocardiogram allows a sonographer to guide a modestly trained individual through the procedure when they’re in a remote or inaccessible region- like the middle of the Pacific Ocean!

1 Levine, BD. Can Intensive Exercise Harm the Heart?: The Benefits of Competitive Endurance Training for Cardiovascular Structure and Function. Circulation. 2014. 130: 987-991.

What will you do with Ben before the swim starts?

The first time we studied Ben with an MRI was a couple of years ago. Since then there have been some new techniques developed for looking at scarring, stiffening, and fibrosis of the heart. We just loaded those sequences onto our magnet [MRI scanner] here at Southwestern, and they’ve already been used by our colleagues in places like Pittsburgh and Chicago. These different scanning sequences can help us learn more about the heart muscle, its connective tissue, and its compliance [the ability of a hollow organ to increase its volume; a measure of how “stretchy” the heart is].

Will you be able to track any changes to Ben’s heart while he’s on the swim?

One of the problems that we have with studying Ben not just before and after – that’s easy! – but over the course of his swim is I can’t fly out to the Pacific Ocean, do an echocardiogram [a test that uses sound waves to produce images of the heart], and then come home again. What we’ve done is that General Electric has provided us with the same echo machine that we use on the space station…and we can actually do a comprehensive echo while Ben is in the middle of the ocean with David [Martin, Ultrasound Lead at the NASA Johnson Space Center Cardiovascular Laboratory] on the phone to guide a crew member through the procedure.

And how often will the crew perform these remote echocardiograms?

About once a month. It doesn’t have to be on an exact day, but once a month would be perfect. Each session should only take between fifteen and thirty minutes to complete.

So, is it dangerous to get “too much” exercise?

There are some people who feel that. My own feeling, and in all our studies in athletes who we studied over decades, is that extreme endurance exercise actually is pretty good for the heart. We don’t know what the peak dose is: is there a level at which there is too much [exercise]? Certainly, if there’s going to be “too much” exercise, swimming across the Pacific Ocean just might be that scenario. So we are particularly interested in studying Ben and his heart.

Do you think that Ben’s heart will have any troubles with this swim?

Ben’s done a lot of swimming in his life and right now, at baseline, his heart looks perfect. His exercise intensity is not going to be that great – it’s a slow, steady pace – and my hypothesis is that his heart’s going to be just fine. But if he gets bitten by a shark I can’t help him!

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