When I was younger, I loved doing distance running. Then I got into triathlons. Now I’m older and wiser and no longer a fan of exercise that is considered “chronic cardio.” Read on to learn about what chronic cardio activities, such as running, may be lacking in achieving optimal fitness.
Marathon runners have higher coronary calcium scores.
Years ago, when I had my traditional internal medicine practice, the coronary calcium score was a relatively new use of CT scanning to evaluate the amount of calcified plaque in the coronary arteries. I was excited to see the results of my first few patients who were signing up to get the heart scan. One of them was a woman in her late 50s who had been a marathon runner for decades. I was shocked that her coronary calcium score (CAC) was not zero and that it was in the range that I was seeing in people who ate poorly and who detested exercise. I recall searching research papers to find that this phenomenon was being seen in marathon runners by others.
In 2019, the study “Assessment of Coronary Atherosclerosis Using Calcium Scores in Short- and Long-Distance Runners found that two of the groups studied found that 73% of runners who had competed in at least 10 ultramarathons and/or Ironman competitions in 10 years and those who had participated in more than 9 marathons over 10 years had CAC over zero. Further, 70% of these runners have scored in the 50th percentile or higher for their age and sex. In the third group of runners who had competed in more than 9 shorter races over 10 years, only 21% had scores over zero, and 19% were in the 50th percentile or higher. The study's conclusion: “A significantly higher rate of coronary artery calcification existed in long-term marathon, ultramarathon, and extreme runners than in submarathon runners. Marathoners and ultramarathoners also had a higher incidence of calcification, as well as higher average plaque burden, as compared to a standard database. Marathoners and ultramarathoners also had above-average coronary calcium scores as compared to a national database.”1
Another study evaluated the CAC in women long-term marathon runners. When compared to sedentary women, they had lower cardiovascular risk. One problem with this study is this comparison. It would be more meaningful to compare the risk to women who are physically fit and active doing non-endurance running.2
“Chronic cardio” exercisers may have more visceral fat.
Visceral fat is unhealthy fat deposits that form around and in the organs. Fatty liver and fatty pancreas are examples of solid organs that can be infiltrated with fat. Visceral fat is not healthy fat to have when it is in excess.
There are times when I'm searching for studies on PubMed, no matter what my search terms I use, I cannot find anything meaningful. At times, I must look elsewhere. Concerning visceral fat, Sean O'Mara, MD, JD makes a compelling point about the amount of visceral fat that is present in people who are long-distance runners compared to those doing HIIT. He proves his point through MRI imaging of visceral fat. His YouTube channel3 has video after video of before and after MRIs of people who are runners who he converts to sprinters.
A September 2020 study compared high-intensity interval training (HIIT) to medium-intensity continuous training (MICT) by using running outside as the exercise for both groups. This study showed the superiority of sprinting to distance running in multiple cardiometabolic parameters. After 8 weeks, the HIT group had improvements in 8 areas (cardiovascular formula, BMI, body fat, visceral fat, systolic blood pressure, total cholesterol, fasting glucose, and triglycerides), while the MICT group only improved in only 3 areas (cardiovascular formula, BMI, and visceral fat). 4 In this study, both groups lowered their visceral fat.
Distance runners have less muscle.
No study is needed to prove this point, and a simple Google search produces compelling results. When googling marathon runners and sprinters and looking at the images, there is a stark contrast between the two groups. The longer the distance a runner runs, the less limb muscle bulk he or she has. The problem with long-distance running is that it results in an energy deficit, which leads to lower fat mass (a good thing) and muscle mass. Endurance muscles are favor white muscle fibers and not the red muscle fibers that are most useful for short bursts of strength and speed. With chronic cardio, the white muscle fibers are favored at the expense of the red.
Instead of chronic cardio...
As I age, I prefer to build and keep as much skeletal muscle bulk as possible. I like to keep my visceral fat as low as possible and although diet is 80-90% of keeping fat healthy, the type of exercise does factor in. With this in mind, there are two types of exercise that provide the most benefit. The best, hands down, is high-intensity interval training or HIIT. The second best is strength exercises, which can include weights, resistance exercises, and calisthenics.
Learn more about HIIT: https://www.savannahfunctionalmedicine.com/post/____%E2%84%8D
1. Jafar O, Friedman J, Bogdanowicz I, Muneer A, Thompson PD, Ling J, Messina A, Yen M, Wakefield D, Varanasi P, Haleem K. Assessment of Coronary Atherosclerosis Using Calcium Scores in Short- and Long-Distance Runners. Mayo Clin Proc Innov Qual Outcomes. 2019 May 27;3(2):116-121. doi: 10.1016/j.mayocpiqo.2019.03.009. PMID: 31193888; PMCID: PMC6543495.
2. Roberts WO, Schwartz RS, Kraus SM, Schwartz JG, Peichel G, Garberich RF, Lesser JR, Oesterle SN, Wickstrom KK, Knickelbine T, Harris KM. Long-Term Marathon Running Is Associated with Low Coronary Plaque Formation in Women. Med Sci Sports Exerc. 2017 Apr;49(4):641-645. doi: 10.1249/MSS.0000000000001154. PMID: 27824692.
3. Gripp F, Nava RC, Cassilhas RC, Esteves EA, Magalhães COD, Dias-Peixoto MF, de Castro Magalhães F, Amorim FT. HIIT is superior than MICT on cardiometabolic health during training and detraining. Eur J Appl Physiol. 2021 Jan;121(1):159-172. doi: 10.1007/s00421-020-04502-6. Epub 2020 Sep 30. PMID: 33000332.
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