I'm a cardiologist, but before that, I was an exercise enthusiast.

I've exercised, I bet, pretty much everyday of my life.

I had two grandfathers who were alcoholics.

But for me, my way of copping with life is exercise.

When I'm nervous, anxious, tired, happy, sad, or whatever,

I exercise, if I have the time, and sometimes even when I don't.

You might have seen me in an airport, waiting for a flight,

running up the down escalator with my backpack on, to kill 20 minutes.

But I always thought that exercise was the best thing for my heart,

and I think that's how I decided, at age 15, I wanted to be a cardiologist.

But now that I am 56 years old, and a lot of decades have gone by,

I've started to have a few warning sings from my heart; a couple years ago

I noticed this, and I got on a mission.

I'm a research cardiologist, and I have a research fellow.

We have been working on this for a couple years,

with the help of some of the brightest cardiologists from around the country,

we came to some startling new insights that seem to emerging about exercise.

This made me think twice about my lifestyle,

and I'm worried that I may have made a lethal mistake.

I hope it's not too late, but let me tell you the story.

So, as I said, I have been exercising for a long time.

But if we go back 2,500 years, there is a guy named Pheidippides

who ran the 26 miles from a battle field

near Marathon, Greece, into Athens

to proclaim the news about a momentous victory over the Persians.

When he arrived at the emperor's throne and said, "Victory is ours,"

he abruptly collapsed and died.

Now, you may have heard that story before,

but what you probably didn't know is that Pheidippides was an accomplished runner.

He'd been a Greek herald messenger his whole life.

He ran a lot of miles everyday,

I bet he was the fittest guy in Athens the day he died.

That's strange.

But now let's go forward two millennia or more.

When the Baby Boomers came of age, another boom happened: the running boom.

If exercise was good for you as anybody could know,

then more had to be better,

and the ultimate test of running and endurance was a marathon.

There was a physician who became famous back in the mid-70s by boldly proclaiming

that if you could complete a marathon, you were immune to heart attack.

This urban myth actually still holds sway with a lot of physicians.

One of my patients and friends is John.

He is 68 now, but he's been running for 45 years.

As he puts it, if he hasn't run twelve miles in a day,

he felt like he was wimping out.

When I saw him, he came into see me, and I said,

"John, let's do a cardiac scan, a CT scan, simple, little, non-invasive,

quick, high tech scan of your heart.

Your arteries, I'm sure, will be soft and supple, clean and healthy.

So that's what a normal cardiac scan should look like:

no calcium whatsoever in these arteries.

His is over here; his score was 1,800.

Anything above zero is abnormal,

anything over 400 is severe; at 1,800, his arteries are harder than his bones!

That can't be good, and he didn't have any other risk factors to speak of.

So in fact, people do die during marathons, but let's be realistic.

If you look at the latest data, the risk is minuscule:

1 in 100,000 participants.

I've gotten to be friends with a guy named Amdy Burfoot.

Amdy won the Boston Marathon in 1968.

He is currently editor-in-chief

and has been a long time editor at large at Runner's World Magazine.

In conversations we've had in recent months, he has challenged me.

"If endurance extreme exercises are so bad, show me the bodies."

He's got a good point; 1 in 100,000 is a pretty low risk.

But I'm not so worried about that;

running is supposed to

add years to your life, and even life to your years.

So, could it be shortening your life expectancy?

I'm not worried about dropping into a risk,

I am just trying to do the right thing, I'm a cardiologist,

I'm the business of finding out the ideal diet and lifestyle.

I'm coming to the conclusion that running marathons

and extreme endurance athletics do not fit into that recipe.

So, that being said, let me be clear about this:

there is no single step you can take in your life

to ensure robust health and remarkable longevity

than a habit of daily exercise.

This is a study of over 400,000 Chinese that was just published last year.

We published an editorial along with this afterwards,

but they found vigorous exercise, this is all cause mortality reduction,

the more reduction the better, and this is minutes of daily exercise,

so 10, 20, 30 minutes of daily exercise.

At 45 or 50, you get a point of further plateau,

so further efforts and time do not appear

to convey further improvements in life expectancy.

Down here is light to moderate exercise: walking, housework,

day to day moving around; just get off your seat and move around.

More is better there; it's not quite as beneficial as vigorous exercise,

but more is better.

You can exercise all day it seems,

without getting yourself in trouble if you keep it down.

So, one of my heroes,

I love evolutionary medicine,

I think if you look in the world of nature and into our deep past,

you can find the template for ideal health, even in our modern world.

Charles Darwin was wrong about one thing though:

it's not the survival of the fittest.

No, in fact it's the survival of the moderately fit, OK?

If the best you can do is walk one flight of stairs

before you have to rest, things are not looking good.

It could be a bumpy ride in the next few years.

On the other hand, if you can dance,

lightly swim, or even jog six miles an hour, that's a ten minute mile,

that's a pretty comfortable pace, right?

Your mortality plummets, and if you, after warming up on a treadmill,

can achieve a speed of seven to seven and a half miles an hour,

you are pretty much bulletproof, when you look at outcomes.

In fact, further attainments of peak fitness do not translate into

further increases in life expectancy.

It plateaus out.

In fact there's even a little trend that it might even go up a little bit.

So, the important concept is that dose makes the poison.

It's true with a lot of things, and if we could come up with a pill

that gave all the benefits that we get from exercise,

I'd be looking for work.

In fact, exercise not only cuts your chance of premature death in half,

but it reduces risk of heart disease, Alzheimer, osteoporosis, depression.

It is an amazing drug, but just like any drug, there is an ideal dose range.

If you don't take enough of it, you don't get the benefit.

If you take too much of it, it could be harmful, maybe even fatal.

When you're sitting here, listening, sitting around like most Americans do,

doing nothing, your hearts pumping, just idling along about a gallon a minute,

about four, five liters a minute.

If you went out, went for a run right now, and you ran hard,

that would go up four, five or even sixfold.

Five, or six gallons a minute!

That is a workout, your heart is working hard,

but that's what it's meant to do, intermittently.

You know maybe 5,10, 30 minutes, and maybe up to 60 minutes

but by 60 minutes something starts happening:

the stretch in the chambers starts overwhelming,

the muscle's ability to adapt,

the catecholamine and adrenaline levels rise,

the free radicals blossom, and it starts burning the heart.

It starts searing and inflaming the inside of your coronary arteries.

We're not really meant for these sustained levels of exercise,

for hours at a time.

If you go to a marathon, and this has been done several times,

you take a troponin level at the end of the marathon,

over half of them will have elevated troponins.

What's a troponin?

Troponin is a sacred chemical to us cardiologists.

When we see that a troponin goes up it means one thing:

heart muscle has died.

Normally, we hop into action because that generally means

there's a heart attack going on, we need to get a vessel open!

In this case, these are little micro tears from the stretching and the searing,

and it's not a big deal if you do it once.

These are little micro tears, they heal;

a few days later it's gone, the heart's back down to normal size.

But if you do this over and over again, the chambers start dialing up,

they get scarred, they get stiff, they thicken.

If you look closely you can see these little white patches

in these veteran extreme endurance athletes accumulate

and for people who have been doing this for years and decades,

their heart becomes older before its time.

We're asking too much of it, it's overwhelming the heart's capacities.

This is a fascinating study done by a cardiologist that I know,

and whose son is also a cardiologist.

These two were both avid runners up in Minnesota.

They did a study looking at the CT scans, like I've shown you of John's,

looked at a group of marathoners who have been doing this for at least 25 years

at least 25 marathons in that time compared to secondary controls.

You can see here that they had 62% more plaque despite fewer risk factors.

People say, "That can't be true."

In fact, a German cardiologist just replicated this study

showing a 108 marathoners with similar findings.

Hard to dismiss.

Veteran endurance athletes also have a five fold increase risk

of atrial fibrillation, a dangerous irregular heart rhythm.

There is sort of an epidemic of this going on among runners

because we've only been doing this for a few decades

and it takes a while for this to develop.

Even more worse, when we see this, as cardiologists, our pupils dilate,

our heart rate goes up; this is ventricular tachycardia,

which is a potentially life threatening rhythm,

and we can see this

from the scarring in the ventricle in some endurance athletes.

So "Born to Run" is a book that was published, a non fiction book,

published just in 2009.

The hero of this story is a guy named Micah True.

He dropped out of American culture,

went down to live with the Tarahumara Indians

in the northern part of Mexico in the Copper canyons.

He was an epic runner,

legendary for his ability to run long distances, hundred mile races.

The Indians down there nicknamed him "Caballo Blanco", the White Horse,

for his ability and his remarkable endurance.

So Micah True died, sadly, at 58 years of age,

on a routine 12-mile run,

in the wilderness of New Mexico, in March of this year.

When they did the autopsy,

they found an enlarged, thickened heart with scar tissues.

The coroner said, "idiopathic cadiomyopathy."

But I've looked at that path report, and it reads like a description

of the pathology we might expect to see in some extreme endurance athletes.

My colleague who wrote some of these papers with me,

Peter McCullough, has coined the term "pheidippides cardiomyopathy."

That's what he had.

There are a couple papers that are coming out in the next two months,

and we're publishing a couple papers as well.

They are going to change the thinking about exercise.

This is one of them by Chip Lavie, one of my colleagues,

and maybe my best friend.

He down in Oshner Clinic in New Orleans, and this is a look at 50,000 runners.

52,000 people followed for decades, on average 15 years but up to 30 years.

They compared the non-runners, about 38,000,

to the runners, about 14,000

and what they found was that runners did live longer, 19% longer,

but if we look closer, you'll see that the runners,

compared to the non-runners, for the risk of death,

the reference is one.

If you ran more 25 miles per week, your benefits went away.

You only got 25-27% reduction in mortality rate.

If you ran between 5 and 20 miles a week, ideally 10-15 miles a week.

When we looked at the running speed, sure enough if you ran too fast,

over eight miles per hour, which is a 7:30 pace,

the benefits went away.