Why Running Marathons Probably Won’t Give You Heart Disease

Dennis Kimetto, setting a new marathon world record in 2014 with a time of 2:02:57. He may be enjoying himself now, but two new studies are making researchers think that his coronary arteries might not be so happy a few years down the road. And yes, he’s a Kenyan.

It shouldn’t be this complicated.

Exercise should be good for your heart.

More should be better.

People who exercise the most should have the healthiest hearts.

Unfortunately, science is not always that simple, even if we try to make it so.

When marathons first became popular, some doctors saw it as an almost fool-proof treatment and cure for heart disease. At one point, there wasn’t a single reported death caused by coronary atherosclerosis in a marathon runner.(1)

Some even suggested that anyone who could finish a marathon was probably immune to heart disease.(2)

This simplistic idea was quickly disproven by data showing there was atherosclerosis and heart damage in otherwise healthy athletes, and it could kill them.(3-5)

In fact, new evidence is starting to show that too much exercise may damage your heart and blood vessels.

While it was naïve to view running marathons as a 100% effective way to prevent heart disease, it’s also inaccurate to condemn lots of exercise as dangerous to your heart, at least for most people.

It’s Time to Get Nerdy, and Exercise Caution

Before we dive into the data, understand that there aren’t many studies that have looked at the relationship between exercise, atherosclerosis, and long-term heart damage. This is both good and bad.

On the one hand, it makes it easy to “nerd out” and carefully examine each study (which we’re about to do.) On the other hand, it means any conclusions we draw are preliminary. A single study, or even a small set of studies, is not firm proof.

That said, we can make a few inferences from this limited data.

The Unsettling Truth about Marathon Running and Heart Disease

 

Some researchers believe that marathon running may accelerate the build-up of plaque in the coronary arteries, possibly leading to heart damage later in life.

In this article, we’re going to focus on two studies that seem to indicate marathon running may increase your risk of heart disease. These two in particular have sparked a good deal of controversy in the research world and elsewhere.

In 2008, German researchers recruited 102 runners who had completed at least five marathons in the last three years. On average, they ran 35 miles (55km) per week. The average age was 57, ranging from 50 to 72. They excluded anyone with a history or symptoms of heart disease and/or diabetes.

After adjusting for other risk factors, they found that the marathoners had more calcium in their coronary arteries (the ones that supply blood to your heart).(6) Higher coronary calcium levels indicate more atherosclerosis.(7)

The number of marathons run was also associated with higher levels of atherosclerosis and more evidence of heart damage. The runners with the most coronary calcium also had more heart damage.

The second study, published the next year on the same group of marathoners, found that 12% had evidence of heart damage. Only 4% of the controls did.(8) The runners with heart damage also had more heart attacks over the next 21 months.

Before burning your running shoes, however, let’s take a closer look at these data.

Does Running Cause Heart Damage, or Is It Less Protective Than We Thought?

There are at least seven reasons it’s not a good idea to get too excited about the results from either of these studies.

1. The difference in the percentage of runners and non-runners with heart damage was not statistically significant. There was an 8% probability (which is small) that the difference in the number of marathon runners with heart damage, and the number of the controls with heart damage, was due to chance.

This means there was still a 92% probability that the difference was not due to chance.

This is not the chance that running caused heart damage. It represents the probability that the difference in the number of non-athletes and runners with heart damage was not a fluke.

Despite not being statistically significant, that’s a small margin, and closer than most runners would probably like. However, even if the results were significant, it’s not clear if marathon running was the cause of this heart damage for several other reasons.

2. There was no record of the runners’ health before the study. It’s possible the runners would have had even worse heart disease if they weren’t runners. It’s also possible the runners could have already had heart disease, and running helped prevent it from getting worse, or helped reverse it.(9,10)

According to Dr. Paul Thompson, a well respected cardiologist and researcher, “they [the runners] might have had terrible numbers before they started running, so when their coronary calcium is compared with folks who are not athletes, but had good risk numbers all their lives, it looks like the runners had more calcium, i.e., more atherosclerosis…”(11)

This idea is more likely, given that “many of the runners ‘got religion’ [started running consistently] when they turned 40 or so,” continues Dr. Thompson. It’s possible that “…these good risk numbers haven’t been their good risk numbers for their whole life, like in the controls, but only since the runners started running. There is a big difference between having good numbers your whole life and only for the last 10 years.”(12)

Another paper analyzing the results of this study concluded that rather than causing heart disease, running “…may uncover underlying CAD [coronary artery disease].”(13)

When you consider that “…more than 50% were former smokers. One can deduce that they had not been sportsmen all their lives but rather took up running relatively late.”(14) It’s possible that if they had been running longer (or not smoking), they might have been healthier, but we can’t tell from these studies.

3. The runners had 8% more previous smokers than the control group in the second study. Other studies have found that smoking is a major risk factor for coronary calcium levels and other cardiovascular problems.(15-17) It’s possible this could have accounted for the higher levels of calcium in the marathon runner’s arteries.

“… given the runners’ smoking history and age, it is conceivable that LGE [heart damage] is solely a result of CAD [coronary artery disease, not caused by running] and the associated endothelial dysfunction,” writes Dr. Kibar Yared, the lead author of an editorial on this study.(18)

It’s possible some of the subjects began running as a means to “…reverse the effects of a decade-long unhealthy lifestyle.”(19) The runners could also have engaged in other unhealthy behaviors, such as being overweight, drinking, and not sleeping enough before the study.

They “…might have been quite unhealthy before they began running. They might have started running as a lifestyle change. They might have had significant atherosclerosis before they started running. Now they still do. It shows up on the calcium scores,” says Dr. Thompson.(20)

4. The marathoners didn’t have many coronary events (heart attacks) — only four over the next 21 months, with no deaths. The researchers weren’t able to collect followup data from the controls, so we don’t know if they might have had more or less heart attacks than the runners.

The followup period was also short (~2 years), and “…it is difficult to predict what will happen to these survival curves 5 and 10 years in the future.”(21) Over the long-term, the runners might have had fewer heart attacks, or more — we don’t know. They may have also had a higher or lower death risk from other diseases like cancer.

5. Some of the marathoners may have had warning signs of heart problems, which is what prompted them to enroll in the study.

The people in the control group were selected at random from the German population. In contrast, the runners were recruited via advertisements, and “who among recreational marathon runners would undergo a lengthy cardiovascular examination which did not include formal performance diagnostics, but rather blood tests and cardiac imaging?”(22)

Who were the subjects in this study? The runners who were worried about their hearts, that’s who.

In these studies, the participants got a much more thorough examination than they would have from their regular doctors.

“There may have been a selection bias favouring runners with health worries to volunteer for this study,” writes Dr. Axel Schmermund.(23)

On the other hand, the lifelong runners from this group could have been more health conscious as a whole (after they stopped smoking), which would have partially negated this recruitment bias.

The researchers were careful to only select people without a history of heart disease or symptoms of ischemic heart disease, but “…the presence of obstructive coronary artery disease (CAD) was not systematically evaluated.”(24)

According to Dr. Erin Karlstedt, the author of another recent study on this topic, this means “it is entirely plausible that the LGE of the LV myocardium [heart damage] observed in the runners… may have been due to underlying occult obstructive CAD [heart disease], rather than as a direct result of repetitive marathon running.”(25)

6. It’s not clear if the higher coronary calcium score is necessarily bad (although it probably is).

“The calcium score does indicate atherosclerosis in the arteries, but we don’t know exactly what that means. For example, we don’t know that all atherosclerosis is bad,” says Dr. Thompson.(26)

In addition to calcified atherosclerosis, which the marathoners had more of, there are also non-calcified forms of atherosclerosis.

It’s possible that extreme training may increase the proportion of calcified atherosclerosis, while not affecting or even reducing the non-calcified forms. The authors correctly point out that there are “no data to support this hypothesis,” and the study did not use techniques that could make this distinction.(27)

On the other hand, “… if the running has caused their [the runners] plaque to become harder and more stable, this is probably a good thing,” continues Dr. Thompson.(28)

Other studies have shown that calcified and non-calcified plaques can progress at different rates,(29,30) and it’s possible exercise may change this progression.

That is, a marathoner might have less non-calcified atherosclerosis, yet more of the calcified form. Some data also indicates that non-calcified plaque is a better marker for myocardial ischemia (a kind of heart damage) than calcium scores.(31)

“A lot of people think that if the plaque is hard and stable — the calcium makes it hard — then this could be a good thing. It’s the soft, unstable plaque that causes blood clots that may lead to heart attacks and strokes. Calcified plaques, like those in Mohlenkamp’s runners, may represent plaques that ruptured and healed on their own.”(32)

Maybe.

A previous study using ultrasound instead of CT scans found that elderly long-distance runners had higher levels of non-calcified plaque than non-runners (although they still had 40% less total atherosclerosis.)(33) That said, CT scans and ultrasound sometimes produce slightly different results, so this isn’t a perfect comparison.(34-37)

Other studies have shown that coronary calcium levels are associated with non-calcified atherosclerosis.(38-40)

Most data also indicates that people with higher levels of calcified atherosclerosis are at a higher risk of having a heart attack, and “coronary calcification clearly does not indicate protection but rather a relevant increase in coronary risk.”(41,42)

All of the runners that had heart attacks also had a calcium score of over 100, so it was also associated with a higher likelihood of heart attacks in this study, as it has elsewhere.

Most studies have shown that having higher coronary artery calcification, like in these runners, is bad. However, there’s still no way to know for sure it was caused by running marathons.

7. Total energy expenditure (a surrogate for training volume) was not associated with coronary calcium levels.

The number of marathons and ultramarathons completed was associated with more atherosclerosis. However, most athletes spend far more time training than racing. If running does contribute to heart disease, you would expect their total training volume to be associated with more atherosclerosis. It wasn’t, despite the runners having over four times the energy expenditure of the controls.

Association is not causation, and this does not prove running doesn’t cause atherosclerosis. Nevertheless, it does challenge the idea that the correlation between running races completed and atherosclerosis was important, because their training volume wasn’t.

Thanks to these variables, “we cannot be certain that marathon running contributes directly to LGE… [heart damage],” writes Dr. Yared.(43)

What You Can Learn from These Two Studies

Given the above factors, the best conclusion you can draw from these studies is that running doesn’t seem to protect your heart from smoking and other unhealthy lifestyle factors as much as you might expect.

The runners didn’t have any less coronary calcium than the controls before adjusting for other risk factors. Despite having higher HDL cholesterol, a lower history of hypertension, lower blood pressure, and a lower total risk for heart disease, they still had about the same amount of coronary calcium.

This does not prove running causes heart disease, as “…there is not enough evidence to implicate marathon running in the development of a dangerous substrate for coronary events.”(44)

The real lesson is that even if you stop smoking and doing other unhealthy activities, a “…conversion to a healthier lifestyle that includes running may not resolve the coronary and myocardial damage…,” concludes Dr. Yared.(45)

What to do if You’re Concerned about Having a Heart Attack

Doctors believe that if you’re over the age of 35, and you have “…a history of smoking, hypertension, and/or hyperlipidemia or a family history of CAD [coronary artery disease]…,” and you want to run marathons, you “…should undergo a thorough medical evaluation…”(46)

This examination “… could include noninvasive CT coronary angiography or cardiac MR imaging…,” to get a better idea of your risk.(47,48)

If you’re an athlete who wants to get tested, the researchers believe that a calcium score of over 100 is a sign that you have a higher risk of having a heart attack during a marathon.(52)

This does not mean that people with a calcium score of over 100 can’t or shouldn’t exercise, but “…it is quite plausible that some subjects with prior risk factor exposure, endothelial dysfunction and increased coronary atherosclerosis are vulnerable to developing further damage in the setting of extreme physical exertion.”(53,54)

These two studies were done on marathoners, but it’s likely the results are relevant for cyclists, swimmers, rowers, and other athletes who train a lot.

Exercise does not make you immune to heart disease. Based on these two studies, however, it’s impossible to tell if lots of exercise causes heart disease.

There are, however, several studies that have tried to answer that question in more detail. We’ll take a look at those in the next article.

You’re reading Part 4 of a series on whether or not exercise damages your heart. Click here to read Part 5.

You can read the first post in this series by clicking here.

P.S. There is also an, as of yet, unpublished study that found higher average levels of calcium in the hearts of 25 marathoners who ran at least one marathon a year for 25 years. I contacted the author in hopes of reviewing the full text and clarifying the specifics, but as of yet I have not gotten a response. Until I do, I’ll just say that it appears to have been an observational study, which can not prove cause and effect.(55)

 

References

1. Bassler TJ. Marathon running and immunity to atherosclerosis. Ann N Y Acad Sci. 1977;301:579-92. Abstract: https://pmid.us/270939 Full Text: NA

2. Noakes T, Opie L, Beck W, et al. Coronary heart disease in marathon runners. Ann N Y Acad Sci. 1977;301:593-619. Abstract: https://pmid.us/270940 | Full Text: Requested, NA.

3. Noakes TD, Opie LH, Rose AG, et al. Autopsy-proved coronary atherosclerosis in marathon runners. N Engl J Med. 1979 Jul 12;301(2):86-9. Abstract: https://pmid.us/449949 | Full Text: Requested.

4. Noakes TD, Opie LH, Rose AG. Marathon running and immunity to coronary heart disease: fact versus fiction. Clin Sports Med. 1984 Apr;3(2):527-43. Abstract: https://pmid.us/6498951 | Full Text: Requested, NA.

5. Noakes TD. Heart disease in marathon runners: a review. Med Sci Sports Exerc. 1987 Jun;19(3):187-94. Abstract: https://pmid.us/3298928 | Full Text: Requested, NA.

6. Möhlenkamp S, Lehmann N, Breuckmann F, et al. Running: the risk of coronary events : Prevalence and prognostic relevance of coronary atherosclerosis in marathon runners. Eur Heart J. 2008;29(15):1903-10. Abstract: https://pmid.us/18426850 | Full Text: https://goo.gl/BHcsX

7. Budoff MJ, Gul KM. Expert review on coronary calcium. Vasc Health Risk Manag. 2008;4(2):315-24. Abstract: http:/pmid.us/18561507 | Full Text: https://goo.gl/S5Bfs

8. Breuckmann F, Möhlenkamp S, Nassenstein K, et al. Myocardial late gadolinium enhancement: prevalence, pattern, and prognostic relevance in marathon runners. Radiology. 2009 Apr;251(1):50-7. doi: 10.1148/radiol.2511081118. Abstract: https://pmid.us/19332846 | Full Text: https://goo.gl/RK4cr

9. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

10. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

11. Burfoot A. Jan. 18: “Exercise is the fountain of youth,” says cardiologist Paul Thompson. Runner’s World. Available at: https://www.runnersworld.com/running-tips/jan-18-exercise-fountain-youth-says-cardiologist-paul-thompson. Jan 18, 2011. Accessed Jan 29, 2011.

12. Burfoot A. Jan. 18: “Exercise is the fountain of youth,” says cardiologist Paul Thompson. Runner’s World. Available at: https://www.runnersworld.com/running-tips/jan-18-exercise-fountain-youth-says-cardiologist-paul-thompson. Jan 18, 2011. Accessed Jan 29, 2011.

13. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

14. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

15. Lehman SJ, Schlett CL, Bamberg F, et al. Assessment of coronary plaque progression in coronary computed tomography angiography using a semiquantitative score. JACC Cardiovasc Imaging. 2009 Nov;2(11):1262-70. Abstract: https://pmid.us/19909929 | Full Text: https://goo.gl/3Ai5D

16. Shaw LJ, Raggi P, Callister TQ, et al. Prognostic value of coronary artery calcium screening in asymptomatic smokers and non-smokers. Eur Heart J. 2006 Apr;27(8):968-75. Abstract: https://pmid.us/16443606 | Full Text: https://goo.gl/ReaQN

17. Poredos P, Orehek M, Tratnik E. Smoking is associated with dose-related increase of intima-media thickness and endothelial dysfunction. Angiology. 1999 Mar;50(3):201-8. Abstract: https://pmid.us/10088799 | Full Text: NA

18. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

19. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

20. Burfoot A. Jan. 18: “Exercise is the fountain of youth,” says cardiologist Paul Thompson. Runner’s World. Available at: https://www.runnersworld.com/running-tips/jan-18-exercise-fountain-youth-says-cardiologist-paul-thompson. Jan 18, 2011. Accessed Jan 29, 2011.

21. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

22. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

23. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

24. Karlstedt E, Chelvanathan A, Da Silva M, et al. The impact of repeated marathon running on cardiovascular function in the aging population. J Cardiovasc Magn Reson. 2012 Aug 20;14:58. Abstract: https://pmid.us/22905796 | Full Text: https://goo.gl/JCwuH

25. Karlstedt E, Chelvanathan A, Da Silva M, et al. The impact of repeated marathon running on cardiovascular function in the aging population. J Cardiovasc Magn Reson. 2012 Aug 20;14:58. Abstract: https://pmid.us/22905796 | Full Text: https://goo.gl/JCwuH

26. Burfoot A. Jan. 18: “Exercise is the fountain of youth,” says cardiologist Paul Thompson. Runner’s World. Available at: https://www.runnersworld.com/running-tips/jan-18-exercise-fountain-youth-says-cardiologist-paul-thompson. Jan 18, 2011. Accessed Jan 29, 2011.

27. Möhlenkamp S, Lehmann N, Breuckmann F, et al. Running: the risk of coronary events : Prevalence and prognostic relevance of coronary atherosclerosis in marathon runners. Eur Heart J. 2008;29(15):1903-10. Abstract: https://pmid.us/18426850 | Full Text: https://goo.gl/BHcsX

28. Burfoot A. Jan. 18: “Exercise is the fountain of youth,” says cardiologist Paul Thompson. Runner’s World. Available at: https://www.runnersworld.com/running-tips/jan-18-exercise-fountain-youth-says-cardiologist-paul-thompson. Jan 18, 2011. Accessed Jan 29, 2011.

29. Schmid M, Achenbach S, Ropers D, et al. Assessment of changes in non-calcified atherosclerotic plaque volume in the left main and left anterior descending coronary arteries over time by 64-slice computed tomography. Am J Cardiol. 2008 Mar 1;101(5):579-84. Abstract: https://pmid.us/18308002 | Full Text: NA

30. Achenbach S, Raggi P. Imaging of coronary atherosclerosis by computed tomography. Eur Heart J. 2010 Jun;31(12):1442-8. Abstract: https://pmid.us/20484566 | Full Text: https://goo.gl/ycVDv

31. Bauer RW, Thilo C, Chiaramida SA, et al. Noncalcified atherosclerotic plaque burden at coronary CT angiography: a better predictor of ischemia at stress myocardial perfusion imaging than calcium score and stenosis severity. AJR Am J Roentgenol. 2009 Aug;193(2):410-8. Abstract: https://pmid.us/19620437 | Full Text: https://goo.gl/JR1QP

32. Burfoot A. Jan. 18: “Exercise is the fountain of youth,” says cardiologist Paul Thompson. Runner’s World. Available at: https://www.runnersworld.com/running-tips/jan-18-exercise-fountain-youth-says-cardiologist-paul-thompson. Jan 18, 2011. Accessed Jan 29, 2011.

33. Galetta F, Rossi M, Franzoni F, et al. Atherosclerosis vascular damage in elderly athletes and sedentary people. Angiology. 1997 Jul;48(7):623-8. Abstract: https://pmid.us/9242160 | Full Text: https://goo.gl/TvCsB

34. van der Giessen AG, Toepker MH, Donelly PM, et al. Reproducibility, accuracy, and predictors of accuracy for the detection of coronary atherosclerotic plaque composition by computed tomography: an ex vivo comparison to intravascular ultrasound. Invest Radiol. 2010 Nov;45(11):693-701. Abstract: https://pmid.us/20479650 | Full Text: NA

35. Gao D, Ning N, Guo Y, et al. Computed tomography for detecting coronary artery plaques: a meta-analysis. Atherosclerosis. 2011 Dec;219(2):603-9. Abstract: https://pmid.us/21920524 | Full Text: NA

36. Voros S, Rinehart S, Qian Z, et al. Prospective validation of standardized, 3-dimensional, quantitative coronary computed tomographic plaque measurements using radiofrequency backscatter intravascular ultrasound as reference standard in intermediate coronary arterial lesions: results from the ATLANTA (assessment of tissue characteristics, lesion morphology, and hemodynamics by angiography with fractional flow reserve, intravascular ultrasound and virtual histology, and noninvasive computed tomography in atherosclerotic plaques) I study. JACC Cardiovasc Interv. 2011 Feb;4(2):198-208. Abstract: https://pmid.us/21349459 | Full Text: NA

37. van Velzen JE, de Graaf FR, de Graaf MA, et al. Comprehensive assessment of spotty calcifications on computed tomography angiography: comparison to plaque characteristics on intravascular ultrasound with radiofrequency backscatter analysis. J Nucl Cardiol. 2011 Oct;18(5):893-903. Abstract: https://pmid.us/21769702 | Full Text: https://goo.gl/IVHAB

38. Taylor AJ, Bindeman J, Le TP, et al. Progression of calcified coronary atherosclerosis: relationship to coronary risk factors and carotid intima-media thickness. Atherosclerosis. 2008 Mar;197(1):339-45. Abstract: https://pmid.us/17727858 | Full Text: NA

39. Javadrashid R, Salehi A, Tarzamni MK, et al. Diagnostic efficacy of coronary calcium score in the assessment of significant coronary artery stenosis. Kardiol Pol. 2010;68:285–291. https://pmid.us/20411452 | Full Text: https://goo.gl/Xfkng

40. Kitamura A, Kobayashi T, Ueda K, et al. Evaluation of coronary artery calcification by multi-detector row computed tomography for the detection of coronary artery stenosis in Japanese patients. J Epidemiol. 2005;15:187–193. Abstract: https://pmid.us/16195639 | Full Text: https://goo.gl/CKx4t

41. Erbel R, Schmermund A. Clinical significance of coronary calcification. Arterioscler Thromb Vasc Biol. 2004 Oct;24(10):e172; author reply e172. Abstract: https://pmid.us/15472132 | Full Text: https://goo.gl/eorCS

42. Polonsky TS, McClelland RL, Jorgensen NW, et al. Coronary artery calcium score and risk classification for coronary heart disease prediction. JAMA. 2010 Apr 28;303(16):1610-6. Abstract: https://pmid.us/20424251 | Full Text: https://goo.gl/Pi0NX

43. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

44. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

45. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

46. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

47. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

48. Rumberger JA, Sheedy PF 2nd, Breen JF, et al. Electron beam computed tomography and coronary artery disease: scanning for coronary artery calcification. Mayo Clin Proc. 1996 Apr;71(4):369-77. Abstract: https://pmid.us/8637260 | Full Text: NA

49. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

50. Parker MW, Thompson PD. Assessment and management of atherosclerosis in the athletic patient. Prog Cardiovasc Dis. 2012 Mar-Apr;54(5):416-22. Abstract: https://pmid.us/22386292 | Full Text: NA

51. Yared K, Wood MJ. Is marathon running hazardous to your cardiovascular health? The jury is still out. Radiology. 2009 Apr;251(1):3-5. Abstract: https://pmid.us/19332839 | Full Text: https://goo.gl/FpfKG

52. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

53. Schmermund A, Voigtländer T, Nowak B. The risk of marathon runners-live it up, run fast, die young? Eur Heart J. 2008 Aug;29(15):1800-2. Abstract: https://pmid.us/18556710 | Full Text: https://goo.gl/OpC48

54. Parker MW, Thompson PD. Assessment and management of atherosclerosis in the athletic patient. Prog Cardiovasc Dis. 2012 Mar-Apr;54(5):416-22. Abstract: https://pmid.us/22386292 | Full Text: NA

55. Schwartz J, Merkel-Kraus S, Duval S. Does elite athleticism enhance or inhibit coronary artery plaque formation. Paper presented at: American College of Cardiology 2010 Scientific Sessions March 16, 2010; Atlanta, GA. Full Text: Requested.

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