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Exercise Volume vs Intensity and the Progression of Coronary Atherosclerosis in Middle-Aged and Older Athletes
Physical activity and exercise training are associated with a lower risk for coronary events. However, cross-sectional studies in middle-aged and older male athletes revealed increased coronary artery calcification (CAC) and atherosclerotic plaques, which were related to the amount and intensity of lifelong exercise. We examined the longitudinal relationship between exercise training characteristics and coronary atherosclerosis.
Middle-aged and older men from the MARC-1 (Measuring Athlete's Risk of Cardiovascular Events 1) study were invited for follow-up in MARC-2 (Measuring Athlete's Risk of Cardiovascular Events 2) study. The prevalence and severity of CAC and plaques were determined by coronary computed tomography angiography. The volume (metabolic equivalent of task [MET] hours/week) and intensity (moderate [3 to 6 MET hours/week]; vigorous [6 to 9 MET hours/week]; and very vigorous [≥9 MET hours/week]) of exercise training were quantified during follow-up. Linear and logistic regression analyses were performed to determine the association between exercise volume/intensity and markers of coronary atherosclerosis.
We included 289 (age, 54 [50 to 60] years [median (Q1 to Q3)]) of the original 318 MARC-1 participants with a follow-up of 6.3±0.5 years (mean±SD). Participants exercised for 41 (25 to 57) MET hours/week during follow-up, of which 0% (0 to 19%) was at moderate intensity, 44% (0 to 84%) was at vigorous intensity, and 34% (0 to 80%) was at very vigorous intensity. Prevalence of CAC and the median CAC score increased from 52% to 71% and 1 (0 to 32) to 31 (0 to 132), respectively. Exercise volume during follow-up was not associated with changes in CAC or plaque. Vigorous intensity exercise (per 10% increase) was associated with a lesser increase in CAC score (β, -0.05 [-0.09 to -0.01]; P=0.02), whereas very vigorous intensity exercise was associated with a greater increase in CAC score (β, 0.05 [0.01 to 0.09] per 10%; P=0.01). Very vigorous exercise was also associated with increased odds of dichotomized plaque progression (adjusted odds ratio [aOR], 1.09 [1.01 to 1.18] per 10% vs 2.04 [0.93 to 4.15] for highest vs lowest very vigorous intensity tertiles, respectively), and specifically with increased calcified plaques (aOR, 1.07 [1.00 to 1.15] per 10% vs 2.09 [1.09 to 4.00] for highest vs lowest tertile, respectively).
Exercise intensity but not volume was associated with progression of coronary atherosclerosis during 6-year follow-up. It is intriguing that very vigorous intensity exercise was associated with greater CAC and calcified plaque progression, whereas vigorous intensity exercise was associated with less CAC progression.
Disclosure statements are available on the authors' profiles:
Exercise Volume Versus Intensity and the Progression of Coronary Atherosclerosis in Middle-Aged and Older Athletes: Findings From the MARC-2 StudyCirculation 2023 Jan 04;[EPub Ahead of Print], VL Aengevaeren, A Mosterd, EA Bakker, TL Braber, HM Nathoe, S Sharma, PD Thompson, BK Velthuis, TMH Eijsvogels
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
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Coronary atherosclerosis in athletes: is exercise volume or intensity the culprit?
Physical activity and athletic participation have long been associated with longevity and reduced atherosclerotic cardiovascular disease events, but recent studies have demonstrated that endurance athletes have more coronary artery calcification (CAC) and atherosclerotic plaque than comparison subjects.1 The Measuring Athletes Risk of Cardiovascular events, or “MARC-1,” study used coronary computed tomography angiography to examine coronary anatomy in healthy, middle-aged (55±7 years) athletes in the Netherlands.2 Athletes with the highest lifelong exercise levels had the highest CAC scores and the highest prevalence of atherosclerotic plaques. MARC-1 also found that the most vigorous exercise was associated with both CAC and plaque prevalence.
The recently published MARC-2 study examined coronary disease progression in 289 of the original 318 MARC-1 athletes to determine whether exercise amount or intensity contributed more to disease progression.3 The amount or volume of exercise was measured as metabolic equivalents of task in hours per week. Exercise intensity was classified (in metabolic equivalents of task) as moderate (3–6 h/wk), vigorous (6–9 h/wk), or very vigorous (>9 h/wk). Both CAC prevalence and score increased over the 6.3±0.5 years of follow-up. Disease progression was not associated with the volume of exercise but was associated with exercise intensity. Vigorous exercise was associated with a smaller increase in CAC. In contrast, very vigorous exercise was associated with both an increase in CAC and mixed plaques, which are thought to be the type of plaque most vulnerable to rupture and erosion.
This apparently paradoxical relationship between lifelong endurance exercise and increased coronary atherosclerosis is an evolving story. Consensus is building that very vigorous exercise is the primary provocateur,1 but it is too early to make exercise recommendations to our patients based on available data. Perhaps the most important clinical message, given the increased frequency of CAC measurement, is to be aware that increased CAC is more common in lifelong athletes but, so far, without firm evidence that this is deleterious. Clinical management is also unclear. I contributed to both MARC studies, so I am frequently referred athletes with high CAC scores. My approach is to reassure patients that atherosclerosis in athletes can occur, including in Clarence DeMar — the seven-time winner of the Boston Marathon4 — without apparent problems but also to treat the athletes’ atherosclerotic cardiovascular disease risk factors aggressively. To paraphrase the WWII rallying cry, “Praise the Lord and pass the ammunition," reassure the patient, but treat the dickens out of his risk factors.
This was a longitudinal study examining the relationship between exercise volume versus intensity and coronary atherosclerosis formation. The authors noted that exercise volume was not associated with changes in coronary artery calcification or plaques. However, very vigorous exercise intensity was associated with the progression of coronary artery calcification in this 6-year study involving 289 patients.
It is unexpected that athletes who engaged in very vigorous–intensity exercise had increased coronary artery calcium scores. Coronary artery calcium score and atherosclerotic plaques are strongly associated with increased cardiovascular events in the general population. However, studies also show that life expectancy is superior in physically active athletic populations compared with the general population. The authors speculate that athletes may have coronary adaptations to exercise and lower-risk plaque morphology, which may account for this population's improved longevity.
Unfortunately, the study did not offer exercise recommendations for either general or athletic populations. Despite worsening coronary atherosclerotic plaques with very vigorous exercise intensity, established studies overwhelmingly support a physically active lifestyle, which leads to improved mortality and morbidity outcomes. The study did not arrive at the following conclusion, which is to question the validity of coronary artery plaque formation in athletes as a reliable marker for cardiovascular risk. I would welcome prospective studies for additional insight.