The Unexpected Side of Endurance Training
Endurance, Cholesterol & Calcium Heart Scores
A few months ago, I received the results of a coronary artery calcium (CAC) score and was surprised by what I saw.
If you’re not familiar, a CAC score measures calcium (plaque) buildup in the coronary arteries, which can indicate future cardiovascular risk.
Like many midlife women, I’ve watched my cholesterol slowly creep up despite consistent exercise, a clean diet, stress management, and good sleep. My dad suffered a heart attack and now has three stents, so out of curiosity, and prevention, I requested the test. I truly expected it to come back clear.
It didn’t.
While my score isn’t high (it’s 20), it bothered me that anything was there at all.
So, I scheduled an appointment with a cardiologist. It took eight months to get in, because “proactive” isn’t usually treated as urgent in our medical system. I wasn’t planning to go on a statin, but I wanted to build a relationship with a doctor and better understand what might be happening in my body.
Similar to past experiences, the visit felt a bit dismissive at first. He talked about how many companies are now adding advanced lipid testing without enough evidence, and how especially where I live, people like me tend to ask questions and get stressed about these tests.
Our medical system is excellent in many ways—but it isn’t designed for prevention.
I made a point to thank him for being patient with my curiosity and desire to learn. Funny enough, the tone shifted instantly. He went from defensive to apologetic. A good reminder: kindness changes conversations.
One area he focused on was my endurance history. How long had I been training? What events had I done?
When I told him I’d been an endurance athlete for over 25 years—starting marathons at 24 and my first Ironman at 28 (with very few women in my age group back then), he said something I did not expect:
That was likely the biggest contributor to my plaque.
WHAT?!
He encouraged me to research it, and sure enough…
Endurance athletes, especially those with high lifelong training volumes, often have paradoxically higher coronary artery calcium scores than sedentary people. The difference is that the plaque in athletes tends to be more stable (calcified) and potentially less risky. Still, high training volume creates unique cardiac stress and requires careful interpretation.
In simple terms: intense, long-term endurance exercise may change the arteries differently than we once thought.
A Note on Oxidative Stress
Oxidative stress is an imbalance between free radicals and antioxidants in the body that can lead to cell damage. It’s involved in conditions like heart disease, cancer, and neurodegeneration.
Exercise naturally increases reactive oxygen species (ROS). In moderate amounts, this is beneficial—it helps the body adapt and become stronger. But very intense or prolonged training can overwhelm antioxidant defenses if recovery and nutrition aren’t sufficient.
Regular, balanced training improves our internal antioxidant systems, while rest and nutrients from real food (not megadoses of supplements) help manage that stress.
What I’m Doing Now
I don’t have perfect answers yet—but I am paying attention.
Cardiovascular disease is the #1 killer of women, and most of us are never taught to look at it preventatively.
I’m not “backing off” being an endurance athlete, but here’s what I’m personally focusing on to support cholesterol and oxidative balance:
Being mindful of saturated fats
Increasing fiber intake
Supporting liver health
Optimizing thyroid function (something many women struggle with—and it directly affects LDL and cardiovascular risk)
Increasing awareness of antioxidant-rich foods
Prioritizing recovery, not just training
If there’s a genetic component, so be it. I’ll focus on what I can control and avoid letting this become another stressor—because chronic stress is often worse than any lab number.
Key Takeaways
A higher CAC score in an endurance athlete doesn’t automatically mean high risk, context and plaque type matter.
Intense exercise creates unique cardiac adaptations that deserve personalized assessment.
The benefits of movement still far outweigh the risks, but this “athlete’s paradox” is worth paying attention to, especially in midlife.
More to come as I keep learning, listening, and asking better questions.
Warmly,
Disclaimer:
The information shared here is for educational purposes only and is not intended to replace medical advice, diagnosis, or treatment. Coronary artery calcium (CAC) scores, cholesterol levels, and cardiovascular risk factors should always be interpreted in partnership with a qualified healthcare provider who understands your personal health history and training background. Exercise, nutrition, and supplement strategies should be individualized based on your labs, genetics, medications, and overall risk profile. Please consult your physician or cardiologist before making changes to your exercise routine, medication, or supplement plan.
