How is an athlete's "enlarged heart" different from an overweight person's?

Exercise causes strain on the heart muscle and a rise in blood pressure. Athletes have enlarged hearts as a result of having to pump more blood, etc etc… but so do chronically obese people. By all accounts I’ve read, exercise from being an athlete is considered good for your heart, the extra work done by your heart in moving your large mass around is considered bad. How is the strain from exercise (or moving external weight)s in a normal person qualitatively different from the strain of moving a larger (fat) body around? How does your heart know the difference?

I’m strictly talking about the effects of weight vs. exercise - assume the two sides being compared both have a vegetarian diet.

I’m disappointed my question is such a dud…

Wait around for a while. I’m totally interested in this too and am also waiting for an authoritative answer. One is bound to come along.

Two hours at this time of day and you think it requies a bump? :dubious: Anyway to answer your queston in grossly simplified terms.

The heart of a fit person is enlarged because it is put under strain intermittently. Even the most ardent athlete will only train seriously for only 6 hours a day. That is enough to encourage the heart muscle to grow stronger, but the corrolary is that the rest of the time the heart is only working at 25% efficiency or less. That means the heart works hard for short periods but is barely idling the rest of the day.

In contrast the enlarged heart of someone with health problems comes from prolonged stress under normal cricumstances. The heart is being asked to work that hard 10 hours a day, and even when the person is asleep the heart is running at 90% capacity. That puts a lot of strain on the organ and risks causing permanent damage. Moreover any minor damage from an infarct that could be insignificant in a healthy person becomes life threatening in such a person because they dsimply don’t have the spare capacity to take up the slack from the temporarily immobilised heart muscle.

I guess you could compare it to putting a V8 engine in a Volkswagon Beetle and in a bulldozer. The VW will be hideously overpowered, but that won’t cause any problems 99% of the time and on those occasions when you do need extra power it’s available, In contrast the bulldozer has the same size engine but it will actually be underpowered and the engine will rapidly burn out because it’s being asked to work way above capacity just to move the vehicle.

Same basic deal with an enlarged heart in an athlete vs the obese. Same size heart, same output, but the athlete’s heart is overpowered for the body’s mainatainance requirements and gets to rest most of the day. In contrast the obese person’s heart is struggling to meet demand from the time they get out of bed and will inevitably wear out.

So if you’re obese and your heart gets bigger, and then you lose a lot of weight and become an athlete, is your heart functionally the same as if you’d been an athlete all along?

Well, it is functionally the same in that it pumps blood. :wink:

Here is a recent news story about cyclists and enlarged hearts.

It appears that the heart can adapt to changing conditions, but that in both cases the reason for the enlarged heart is the increased demand placed on the heart. I’d guess that as long as the demand on the heart stayed the same during the transition from obese to athlete, there would be no change.

However, the heart is just one part of the cardiovascular system, and the overall fitness of the athlete will be far superior to the obese person. An athlete can recover (i.e., return to a normal heart rate) from an intense effort much faster due to this fitness.

[Slightly off topic]
It seems the enlarged “athlete’s heart” isn’t merely limited to humans. Take, for example, famed racehorse Secretariat, who’s heart was exceptionally larger than that of a typical horse.

[/slightly off topic]

“Enlarged Heart” Is a vague term. Cardiomegaly* is the medical term.

The term includes hypertrophy^ of either the left or right ventricles, L or R atria or dilation.

Athletes usually have left ventricular hypertrophy, because, just like the other muscles they use, the heart muscle becomes larger. This is not a dangerous condition, when caused simply by excercise. The chambers become more efficient, pumping more oxygen and nutrients to the tissues. The blood vessels remain normal, so blood pressure remaims normal.

It is dangerous if caused by any of several other factors, including obesity. In obesity, the heart is also asked to work overtime. It becomes larger as vessels narrow with hypertension. In other words the heart musle has to enlarge to send the same amount of blood to the tissues. Over time, the heart loses the ability to keep up, so blood pressure goes up even more, while the tissues are recieving less and less of what they need.

There are several other reasons for cardiomegaly, including infection, called cardiomyopathy, but I think I’ve addressed the two areas of your question. I’ve tried to keep it simple, if you need more information, see*

*Wikipedia article. Google for more indepth explanations
^Medicalese, for enlargment.

I’m obese and have LVH, but have no other symptoms or health problems except minor PVC. I take Toprol 50mg daily for palpitations, which could or could not be from my LVH. Who knows? IANAD, but I personally feel that an enlarged heart is an enlarged heart. Strain on your heart is strain on your heart. I’ve always said that I think jogging is actually bad for your heart.

Our hearts were only designed to pump that hard during fight or flight, yet we FORCE them to pump that hard when exercising. We’re tha only animals that do that to ourselves. Ask Jim Fixx I’m sure he knows about jogging and the stress caused to the heart and vascular system… :wink:

Either way, I need to get my gastric bypass, I’m hoping my heart will go back into shape after that happens.

First of all the left ventricular hypertrophy in athletes doesn’t "strain their hearts, it is a compensation for increased exercise, exibited by a lack of hypertension. The Toprol you take is helping keep your blood pressure within range, that doesn’t mean your vessels aren’t narrowed.
The LVH isn’t a disease, it can be a sign of disease, or not.

Jim fix died from coronary artery disease, yet a different problem. He had a strong family history, his father died of the same thing at an early age.

He may or may not have had LVH, but if he did, it didn’t contribute to his death.

Mr. Fixx’s genetics notwithstanding, exercise is good for the heart. Even though we can’t change our genetics, we can change many other factors that increase our chances of living a full and healthy life.

I’m sorry to interrupt, but antelopes run, cats and dogs fight, and birds fly to stay in shape and generally keep themselves prepared for life. Humans aren’t anywhere close to the only animals that play and exercise; in fact we probably do it far less than other species, on average.

That’s not even remotely true. You try climbing 100 feet up a tree to collect a beehive, or run for 4 hours chasing an antelope, or swim a kilometre to cross a river and see how hard your heart is working when you finish.

Human hearts evolved to cope with all those conditions and many more on a daily basis. None of those are flight or fight situations.

To say that the human heart was only designed to work hard under conditions of danger has no basis in relaity whatsoever. Human hearts were designed to work hard periodically for extended periods every single day under normal food gathering conditions.

You have apparently never seen any animal play.

Huh? What does a blockage to blood vessel have to do with damage caused by jogging?