Endurance exercise and heart health, is there a definitive link? The idea that endurance exercise like running marathons and riding long distance bike races may be harmful rather than beneficial to the heart has been around for a very long time. In the year 490 BC, the fittest runner in Greece, Phiddipides, ran 26 miles from Marathon to Athens, to announce a great victory over the Persians. After declaring the news, he dropped dead.
More recently, several studies have reported on endurance exercise and heart disease, often using coronary artery calcification on CT scanning as a measure of atherosclerosis. Two new studies have been reported and will be discuss but first some of the data that preceded it is worth reviewing.
In 2013, the MESA research group published data relating self-reported physical activity and both coronary artery calcification (CAC) and ankle brachial index (ABI) studies. Mean age of participants was 61 years, 53% were female, and mean body mass index was 28 kg/m(2). After adjusting for traditional cardiovascular risk factors and socioeconomic factors, intentional exercise was protective for incident peripheral artery disease based on ABI measurements. After adjusting for traditional cardiovascular risk factors and socioeconomic factors, there was a significant, but small, association between vigorous PA and lower incident CAC. Unlike the protective effect of exercise measured on CAC and ABI studies, sedentary behavior was associated with increased CAC scores.
Endurance Exercise and Heart Health
In 2019, the Cooper Center in Dallas, Texas reported on physical activity, CAC, and all-cause and cardiovascular mortality. Among the 21 758 male participants, baseline mean (SD) age was 51.7 (8.4) years. Men with at least 3000 MET-min/wk were more likely to have prevalent CAC of at least 100 AU (relative risk, 1.11; 95% CI, 1.03-1.20) compared with those accumulating less physical activity. In the group with physical activity of at least 3000 MET-min/wk and CAC of at least 100 AU, mean (SD) CAC level was 807 (1120) AU.
After a mean (SD) follow-up of 10.4 (4.3) years, 759 all-cause and 180 CVD deaths occurred, including 40 all-cause and 10 CVD deaths among those with physical activity of at least 3000 MET-min/wk. Men with CAC of less than 100 AU and physical activity of at least 3000 MET-min/wk were about half as likely to die compared with men with less than 1500 MET-min/wk (hazard ratio [HR], 0.52; 95% CI, 0.29-0.91). In the group with CAC of at least 100 AU, men with at least 3000 MET-min/wk did not have a significant increase in all-cause mortality (HR, 0.77; 95% CI, 0.52-1.15) when compared with men with physical activity of less than 1500 MET-min/wk. In the least active men, those with CAC of at least 100 AU were twice as likely to die of CVD compared with those with CAC of less than 100 AU (HR, 1.93; 95% CI, 1.34-2.78).
The researchers concluded the study provided evidence that high levels of physical activity (≥3000 MET-min/wk) are associated with prevalent CAC but are not associated with increased all-cause or CVD mortality after a decade of follow-up, even in the presence of clinically significant CAC levels. So, what evidence links endurance exercise and heart health – and how is that association demonstrated?
Two Studies
As mentioned, there are two new studies by the same research group. In the first study, the Cooper Clinic in Dallas, Texas reported on physical activity and the progression of CAC in men and women. This cohort study included data from 8771 apparently healthy men and women 40 years and older who had multiple preventive medicine visits at the Cooper Clinic (Dallas, Texas), with a mean (SD) follow-up time of 7.8 (4.7) years between the first and last clinic visit. Participants with reported PA and CAC measurements at each visit during 1998 to 2019 were included in the study. Data were analyzed from March 2023 to February 2024.
Among 8771 participants, the mean (SD) age at baseline was 50.2 (7.3) years for men and 51.1 (7.3) years for women. The rate of mean CAC progression per year from baseline was 28.5% in men and 32.1% in women, independent of mean PA during the same time period. Baseline PA was not associated with CAC progression to a clinically meaningful threshold of 100 AU or more over the follow-up period. The authors concluded that PA volume was not associated with progression of CAC in a large cohort of healthy men and women who were initially free of overt cardiovascular disease.
The second new study was also from the Cooper Clinic and examined the relationship between lower intensity versus longer duration physical activity and CAC. Data are from 23,383 apparently healthy men who completed a PA questionnaire and underwent CAC scanning as part of a preventive exam. Higher average intensity of PA was related to lower mean CAC (-3.1%/MET, 95% confidence interval [CI]: -4.6, -1.6%/MET) and lower relative risk (RR) of CAC ≥ 100 AU (RR: 0.99, 95% CI: 0.98, 1.00/MET). Opposite trend was observed for the duration component wherein higher weekly duration of PA was significantly associated with greater mean CAC and RR of CAC ≥ 100 AU. The researchers concluded that elevated CAC was associated with lower average intensity and longer duration of PA in men, providing new insight into the complex relationship between leisure-time PA behaviors and risk of CAC.
What Does It Mean?
What is to be made of these studies? One limitation of using CAC as a measure of atherosclerosis is it cannot measure “non-calcified” plaque and cannot measure vessel stenosis. These studies could not report on duration or intensity of exercise and these important parameters of coronary atherosclerosis. With the data available, it is reassuring that fitness buffs with high calcium scores do not, in general, have a higher risk of premature death. It is also comforting that higher loads of exercise do not accelerate the progression of CAC but the CAC will go up in all patients over time. Many patients are hopeful that their CAC score will drop over time with lifestyle and medical therapy and need to be educated that this is not to be anticipated. It can even be argued that a follow-up CAC score after a first abnormal one is unnecessary as it will always be higher.
Advanced preventive cardiology clinics, like mine, have moved from CAC scoring to quantitative coronary CT angiography with AI analysis providing plaque characterization and degree of stenosis. Further studies in athletes will be needed using this advanced imaging technique to more fully understand the relationship between the duration, the intensity, and the type of exercise with changes in coronary morphology and outcome.
