Intense Exercisers

Exercisers Have More Stable Plaques

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Two breakthrough studies have given the best explanation yet of how exercise helps to prevent heart attacks. Competitive older endurance athletes may have more plaques in their arteries than non-exercisers, but they have the type of plaques that are far less likely to break off and cause heart attacks (Circulation, April 27, 2017;136:138-148; May 2, 2017;136:126-137).

The studies showed that competitive master athletes have:
• low 10-year-history risk scores for likelihood to suffer heart attacks (Framingham study data)
• higher plaque thickness
• more calcium in their plaques
• more stable plaques that are far less likely to break off to cause heart attacks. By comparison, more than 61.5 percent of the older men who did not exercise regularly had “mixed morphology” plaques with much higher risk for breaking off to cause heart attacks.

An editorial accompanying these studies states that having more stable plaques can explain why endurance athletes have such a low rate of heart attacks, and increasing endurance training also increases protection from heart attacks. Michael Joyner of the Mayo Clinic said that the papers show that “Stable plaques plus larger coronary arteries that dilate more in high volume exercisers should be highly protective against coronary events.”

How Plaques Form in Arteries
If you understand what happens during a heart attack and what causes these events, you will be able to see why plaque stability is so important. Your immunity is good for you because it helps to protect you from infections. When a germ gets into your body, your immunity makes cells and proteins that attack and kill germs. When the germs are gone, your immunity is supposed to dampen down. However, if your immunity stays active all the time, it can use the same cells and chemicals to attack you to increase your risk for a heart attack.

Different types of bacteria that live in your colon turn your immunity on and off. What you eat determines which types of bacteria grow in your colon because these bacteria eat the same food that you do. These colon bacteria determine how quickly you form plaques in your arteries. Foods favored by the bacteria that turn on your immunity are classified as pro-inflammatory and increase risk for forming plaques in your arteries to increase risk for heart attacks. Anti-inflammatory foods are favored by types of bacteria that help to prevent plaques from forming and decrease heart attack risk. A diet that is high in whole grains, fruits and vegetables, and legumes and nuts is associated with reduced risk for cardiovascular disease, while less healthful diets that are high in sweets, refined grains, juices, red meats and processed meats are associated with increased risk (Journal of the American College of Cardiology, Volume 70, Issue 4, July 2017).

When your immunity stays on all the time to cause inflammation:
• Immune cells and proteins can punch holes in your arteries in the same way that they punch holes in the membranes of invading bacteria.
• The holes bleed and clot.
• Plaques form at the site of the clots and start to cover the inner linings of arteries. We know that cholesterol isn’t the primary cause of forming plaques because cholesterol does not start to show up in plaques until long after the holes, bleeding and clotting have occurred on the inner linings of arteries.

Breaking Off of Plaques Causes Heart Attacks
A heart attack is a sudden complete obstruction of the blood flowing to part of the heart muscle. A 90 percent blockage of an artery does not cause a heart attack because blood can still flow through and the heart muscle can still get some oxygen. A heart attack is not caused by plaque buildup on the inner lining of arteries; it is caused by a sudden breaking off of a plaque, followed by bleeding where the plaque broke off. Then clots form at the bleeding sites. Next, the clot extends to block completely the flow of blood to the part of the heart muscle supplied by that artery. The part of the heart muscle deprived completely of blood flow then dies.

How Doctors Measure Plaque Stability
A CT scan can show how stable plaques are (American Journal of Roentgenology, March 2015;204(3):W249-W260). X rays can show the difference between stable plaques that are safe and those that are unstable and more likely to break off to cause heart attacks. Signs of plaque stability include extensive calcification, less lipid-rich areas, increased fibrous areas and structural changes.

Amount of Exercise Does Not Determine Amount of Plaques
A new study shows that older men (average age 60), who had run marathons for 26 to 34 years and completed 27 to 171 marathons, had plaques in their arteries that were related to their own risk factors for heart attacks and not to the number of miles or marathons they had run (Med & Sci in Sports & Ex, July 17, 2017). This suggests that plaques in arteries are not caused by endurance training, but are caused by other factors such as a pro-inflammatory diet, high blood pressure, high cholesterol and previous use of tobacco.

Recommendations
• To help prevent or reduce plaque formation, follow a heart-attack-preventing diet that is high in anti-inflammatory foods and low in pro-inflammatory foods. This means that you should eat plenty of plants and restrict red meat, processed meats, sugar-added foods, all sugared drinks and fried foods.
• Avoid overweight
• Do not smoke
• Limit or avoid alcohol
• To stabilize existing plaques and widen your coronary arteries, try to exercise every day for at least a half hour a day. Exercising more than that may be even more protective.

Intense Exercisers Have More Plaques but Fewer Heart Attacks

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The MARC-2 study followed 291 older men for 6.3 years with a test called Coronary Artery Calcification (CAC), and found that the amount of calcium in the arteries leading to the heart increased most in men who exercised at the highest intensity, even more than those who exercised the most (Circulation, January 4, 2023). The authors said this showed that intense exercise increases the amount of plaques in arteries, which may be true. However, they would then have to explain why intense exercisers are far less likely to suffer heart attacks than non-exercisers (JAMA Cardiol, 2019;4(2):174-181). Exercise is prescribed both to treat and to prevent heart attacks (Front Cardiovasc Med, Feb 3, 2021;8:753672).
• CAC measures only the size of plaques. It does not measure obstruction of blood flow to the heart. Furthermore, as plaques form, the involved arteries usually widen to accommodate the plaques (JAMA Cardiol, October 27, 2021).
• Intense exercise increases the amount of calcium in plaques (Circulation, January 4, 2023). Calcium in plaques stabilizes them to help prevent plaques from breaking off, which is the cause of most heart attacks.

Heart Attacks Are Caused by Plaques Breaking Off from Coronary Arteries
Heart attacks have little to do with arteries being narrowed by plaques. A heart attack is caused by a sudden immediate complete blockage of blood flow to the heart muscle itself. First a plaque breaks off from the inner lining of an artery leading to the heart. This is followed by bleeding and clotting. Then the clot extends to block all flow of blood through that artery to deprive the heart muscle completely of oxygen, so that part of the heart muscle dies.

An X-ray test called Coronary Artery Calcification Score or Calcium Artery Score (CAC) is used to measure the size of plaques in the arteries leading to the heart. That test can also tell whether the plaques are very stable, or are unstable and more likely to break off to cause a heart attack. A stable plaque is called “hard; ” it is not full of fat and has a thick calcium periphery to keep the plaque in place. An unstable plaque is called “soft;” it is full of fat and has irregular calcium borders that may not hold the plaque in place.

Plaques are Formed from an Unhealthful Diet
Exercise does not prevent plaques from forming. A diet that is high in the pro-inflammatory foods (sweets, refined grains, sugared drinks, red meat, processed meats, fried foods, alcohol) is associated with increased risk for forming plaques (Journal of the American College of Cardiology, July 2017;70(4)). A heart-attack-preventing diet that is high in vegetables, fruits, whole grains, beans, seeds and nuts will reduce your chances of growing larger plaques. You also should avoid being overweight or smoking.

Why Exercisers May Have Higher Calcium Scores
Competitive older endurance athletes can have more plaques in their arteries than non-exercisers, and intense exercise may increase plaque formation. However, the endurance athletes are likely to have the type of plaques that are far less likely to break off to cause heart attacks (Circulation, April 27, 2017;136:138-148; May 2, 2017;136:126-137). Plaques form in arteries from an unhealthful diet and perhaps faulty genes. Exercise does not prevent plaques from forming, and a pro-inflammatory diet increases plaque formation regardless of exercise. Exercise stabilizes plaques so that they are less likely to break off to cause heart attacks. Since exercise burns lots of extra calories, exercisers may eat more food, and if they choose to add more pro-inflammatory foods, they can expect to build up more plaques.

My Recommendations
A high Coronary Artery Calcium test (CAC) has been shown to be associated with increased risk for a heart attack, but regular exercisers may have higher CAC test results because they have more calcium in their plaques. These more stable plaques are less likely to break off and cause a heart attack. Since exercise stabilizes plaques to help keep them from breaking off from arteries, exercise should be part of your heart-attack-prevention program. You should check with your doctor about exercising if you have evidence of heart disease caused by a faulty diet: high blood cholesterol, triglycerides, sugar or CRP, high blood pressure, an abnormal EKG, or chest pain particularly with exercise.

Journal References on Coronary Artery Calcium Tests (CAC)
• CAC measures amount of plaques in a person’s arteries (J Am Coll Cardiol, 1998;31:126–33).
• CAC is an excellent predictor of likelihood to suffer a heart attack in both younger and older men (Am J Epidemiol, 2005;162:421–9; Eur Heart J, 2008;29:2782–91; J Am Coll Cardiol, 2018 Jul 24; 72(4): 434–447).
• CAC measures the size of plaques in a person’s heart arteries (J Am Coll Cardiol, 1998;31:126–33).
• Physical activity increases CAC progression (Heart, Nov 2021;107(21):1710-1716).
• Increased CAC associated with increased heart attack risk (Am J Cardiol, 2017 May 15;119(10):1584-1589).
• Life-long middle-aged male endurance athletes have high CAC scores (European Heart J, July 21, 2021;42(28):2737–2744)