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Does High Intensity Exercise Damage Arteries and Impact Heart Health?

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Can exercising be bad for your heart? Starting in the early 1980s several studies showed an association between endurance exercise and coronary artery disease. [1] Since the discovery of this unexpected finding, follow-up studies have been able to determine that risk of cardiovascular events is still lower compared to sedentary people. Aengevaeren et al [2] investigated whether there were differences between runners and cyclists. They found that cyclists had less arterial plaque compared to runners. The majority of the data was collected from white, middle-aged men.

It is common for health minded individuals over 40 to get coronary artery calcium (CAC) tests. My athletic patients are always shocked when they discover they have above average amounts of calcified plaque in the coronary arteries. The notion that a fit individual may have more plaque compared to less fit people, but less risk of a coronary event can be confusing.

Types of Arterial Plaque

There are three types of plaque: calcified, noncalcified, and mixed. Coronary artery calcium analysis only reveals the calcified type. The type of plaque that athletic endurance individuals develop is denser and more calcified rather than mixed or soft. This is the least risky type of plaque. This “accelerated calcification” is a healing response that can be increased by statin use. It is for this reason that conventional calcium scoring may not be adequate to determine effectiveness of treatment. It is hard to know if the patient is healing the plaque or building more. A Coronary CT angiogram (CCTA) must be done to determine what types of plaque are present. 

High Intensity Exercise and Heart Health

But what about the intensity of exercise and heart health? A recent January 2023 study [3] in the Journal Circulation made the assertion that it was exercise intensity but not volume that was associated with progression of coronary atherosclerosis.

The study aimed to evaluate the relationship between exercise volume, intensity, and the progression of coronary atherosclerosis in middle-aged and older male athletes over a period of six years. The findings suggest that exercise intensity, rather than volume, was associated with the progression of coronary atherosclerosis. “Vigorous” exercise was linked to lesser progression of coronary artery calcification (CAC), while “very vigorous” exercise was associated with greater progression of CAC and atherosclerotic plaques. Specifically, very vigorous exercise was related to increased odds of plaque progression, especially calcified plaques. The study highlights the importance of considering exercise intensity in understanding the effects on coronary health in athletes. Additional research is needed to explore the cardiovascular risk implications of these findings.

In this study, 71% of the athletes performed more than one sport, making it hard to completely differentiate between popular endurance sports such as cycling and running.

How is Vigorous Exercise Defined?

So, just what is “very vigorous”? In the study they defined very vigorous as a METs >9 (Metabolic Equivalent of Task). So, what the heck does this mean? This should help put it in perspective:

  • 7 mph running is 8:33 pace which is about 11.5 METs
  • According to the ACE 2011 Compendium of Physical Activities[4] bicycling or mountain biking uphill vigorously is assigned a MET value of 14
  • Stationary cycling with average watts between 90 and 100 was defined as moderate to vigorous and assigned a MET of 6.8. This obviously depends quite a bit on the weight, age, gender, and fitness of the individual. For me that would be about the easiest I could go.

So, I think it is clear that if you are competitive, you are going way above 9 METs. When I look at the numbers for vigorous exercise it is more recreational.

Examining the Link Between Endurance Athletes and Arterial Plaque

How and why do endurance athletes who trained at high intensities get more arterial plaque? The current state of thinking blames higher stress hormone levels, oxidative stress, and mechanical strain. The stress hormones (catecholamines) go up exponentially with higher intensity. Catecholamines increase heart rate and blood pressure, which increases the mechanical stress on the artery wall.  Increased heart rate also causes shear stress and turbulent blood flow which also causes mechanical stress on the artery wall. Catecholamines have also been shown to increase oxidative stress, a key part of arterial plaque initiation. They do this through a process called auto oxidation. This is how a high stress lifestyle can cause accelerated aging. The way I describe it, particularly for runners, is this: the combination of foot strike and high heart rate create mechanical stress on the coronary arteries. Imagine the heart jiggling while beating hard at the same time.

Should Athletes Stop High Intensity Exercise?

What should you do then; stop exercising so hard? I am assuming many of you who are reading this have known someone who had a heart attack despite appearing super fit and healthy previously. You might also be someone who has had coronary calcium scoring done and was shocked to see that you were way above average on your plaque volume.

Should you stop exercising or stop racing? I say not. Instead, what you need is a thorough workup.

Preventative Cardiology Testing

Here is what my patients receive for preventative cardiology testing:

Echocardiogram to screen for heart valve dysfunction, pathologic remodeling which can include ventricular wall fibrosis, pulmonary hypertension, inappropriate thickening and atrial dilation. Exercise-induced hypertension is often a missed diagnosis and increases risk considerably. The only way to test this is to exercise with a blood pressure cuff.

Coronary artery calcium is tested and if abnormal the patient receives a follow-up coronary CT angiogram with analysis through Cleerly health (

Detailed blood testing to look at all the novel risk factors:

  • Advanced lipid panel with inflammation and oxidized LDL offered by Cleveland heart lab/ Quest diagnostics. This panel includes quite a bit of information including a detailed look at arterial inflammation.
  • ProBNP to determine heart muscle stress
  • High-sensitivity troponin to determine if there is low-level ischemia and heart muscle damage
  • Ferritin to make sure iron is within normal limits. Excessive iron causes oxidative stress and increases the risk of multiple diseases.
  • Complete blood count to screen for excessive red blood cell count which increases blood viscosity
  • Comprehensive metabolic panel
  • Hemoglobin A1c
  • TSH
  • Vitamin D

Exercise training can lower the risk of major adverse cardiovascular events by up to 40%. It is critical to do a preventive minded evaluation of “older” endurance athletes. By evaluating plaque burden and risk factors true risk can be assessed. It is by collecting this data that the implementation of an individualized treatment plan to lower the risk of a coronary event can be implemented.

I am available for consultations including the entire workup for anyone interested in determining the risk and whether it safe to keep exercising hard.

Contact NatureMed to schedule your appointment with Dr. Steve Parcell: 303-884-7557.


[1] Aengevaeren VL, Mosterd A, Sharma S, Prakken NHJ, Möhlenkamp S, Thompson PD, Velthuis BK, Eijsvogels TMH. Exercise and Coronary Atherosclerosis: Observations, Explanations, Relevance, and Clinical Management. Circulation. 2020 Apr 21;141(16):1338-1350. doi: 10.1161/CIRCULATIONAHA.119.044467. Epub 2020 Apr 20. PMID: 32310695; PMCID: PMC7176353.

[2] Aengevaeren VL, Mosterd A, Sharma S, et al. Coronary atherosclerosisin athletes: exploring the role of sporting discipline. JACC Cardiovasc


[3] Aengevaeren VL, Mosterd A, Bakker EA, Braber TL, Nathoe HM, Sharma S, Thompson PD, Velthuis BK, Eijsvogels TMH. Exercise Volume Versus Intensity and the Progression of Coronary Atherosclerosis in Middle-Aged and Older Athletes: Findings From the MARC-2 Study. Circulation. 2023 Mar 28;147(13):993-1003. doi: 10.1161/CIRCULATIONAHA.122.061173. Epub 2023 Jan 4. PMID: 36597865.