Heart Health: New Study Reveals How Exercise Intensity Matters More Than Volume (MARC-2 Research)
For athletes, exercise intensity trumps volume for heart health! (MARC-2 Study). Discover how vigorous vs. very vigorous workouts impact coronary artery calcification. Learn how to optimize training for a healthy heart.
DR ANITA JAMWAL MS
4/7/20246 min read
The MARC-2 study, published in the journal Circulation, examined how exercise intensity affects coronary artery health in middle-aged male athletes. Unlike expectations, overall exercise volume wasn't linked to artery calcification (CAC) progression. However, intensity mattered: vigorous exercise slowed CAC increase, while very vigorous exercise accelerated it, particularly calcified plaque formation. This challenges the usual view of high-intensity exercise being universally good for the heart. Researchers suspect increased hormone levels and inflammation caused by very vigorous exercise might contribute. Despite a higher CAC, athletes often live longer. This could be due to exercise adaptations in the arteries or the type of plaque being less risky. The study highlights the complexity of exercise intensity and its impact on athlete's heart health.
Key points
Study Focus: Investigated the association between exercise characteristics and the development of coronary atherosclerosis in a group of middle-aged and older male athletes.
Design and Participants: The study followed 289 athletes from a previous study (MARC-1) for 6.3 years. Used CT scans to measure the CAC score and assess plaque presence/severity at the beginning (MARC-1) and end (MARC-2) of the study.
Exercise Characteristics: Measured exercise volume (MET-hours/week) and intensity (moderate, vigorous, very vigorous). Assigned MET scores to different sports based on intensity.
Key Finding - Exercise Volume: No significant link between overall exercise volume during follow-up and coronary atherosclerosis progression. This might be due to the shorter follow-up period compared to the lifetime assessed in the previous study (MARC-1).
Key Finding - Exercise Intensity: Exercise intensity played a crucial role:
Vigorous exercise (moderate intensity) is associated with a slower increase in CAC score, suggesting a potential protective effect.
Very vigorous exercise (high intensity): linked to a faster increase in CAC score and a higher chance of plaque progression, particularly calcified plaques. This challenges the traditional view of high-intensity exercise being universally beneficial for cardiovascular health.
Potential Mechanisms: Researchers propose mechanisms for the unexpectedly vigorous exercise finding:
Increased Catecholamine Levels: Very Vigorous exercise may elevate catecholamine hormones, which could increase coronary stress and disrupt blood flow, potentially promoting atherosclerosis.
Inflammation: Very vigorous exercise might induce long-lasting inflammatory changes in immune cells, potentially contributing to plaque formation.
Clinical Relevance: While athletes have a higher CAC and plaque prevalence, they also have a longer lifespan. This could be due to:
Beneficial Adaptations: Exercise training might induce favorable adaptations in coronary arteries, mitigating CAC risks.
Lower Risk Plaque Morphology: The type of plaque formation in athletes might be less prone to complications compared to the general population.
Additional Notes:
The study has limitations, including a male-only and predominantly white participant group.
Future research should consider a more diverse population, longer follow-up periods, and explore specific exercise types within intensity categories.
For decades, exercise has been touted as a cornerstone of cardiovascular health. However, recent studies have revealed a surprising wrinkle in this narrative - athletes, despite their active lifestyles, may exhibit a higher prevalence of coronary artery calcification (CAC). This paradox prompted researchers to delve deeper into the connection between exercise characteristics and the development of atherosclerosis in athletes. The MARC-2 study aimed to illuminate this complex relationship.
Study Design and Participants:
MARC-2 stands for "Measuring Athletes' Risk of Cardiovascular Events 2" and serves as a follow-up to the previous MARC-1 study. The study focused on a cohort of 289 middle-aged and older male athletes who underwent CT scans at the beginning (MARC-1) and end (MARC-2) of the study, spanning 6.3 years. These scans assessed coronary artery health using CAC scoring and coronary computed tomography angiography (CCTA). Researchers meticulously collected information on the athletes' exercise routines through questionnaires, capturing details like type, duration, frequency, and intensity of their workouts. They then assigned a metabolic equivalent (MET) score to each sport to quantify exercise intensity and calculated exercise volume as MET hours per week.
Key Findings:
The central theme emerging from MARC-2 was the unexpected influence of exercise intensity on coronary atherosclerosis progression, with exercise volume playing a secondary role. Here's a breakdown of the key observations:
Exercise Volume: Contrary to expectations, no association was found between overall exercise volume during the follow-up period and the progression of coronary atherosclerosis. This finding contrasts with the results of MARC-1, a cross-sectional study, which suggested a link between lifelong exercise volume and higher CAC prevalence in athletes. The researchers propose that the shorter follow-up duration in MARC-2 (compared to the lifetime assessed in MARC-1) might be insufficient to detect an effect of exercise volume on CAC or plaque progression.
Exercise Intensity: This is where things get interesting. The study revealed a contrasting association between exercise intensity and CAC progression:
Vigorous Exercise: This level of exercise intensity, characterized by moderate intensity workouts, was associated with a slower increase in CAC score. This implies a potentially protective effect of vigorous exercise on coronary artery health.
Very Vigorous Exercise: In contrast to vigorous exercise, very vigorous exercise, involving high-intensity workouts, was linked to a faster increase in CAC score and a higher likelihood of plaque progression, particularly calcified plaques. This finding challenges the traditional perception of high-intensity exercise being universally beneficial for cardiovascular health.
Unraveling the Mechanisms:
The observed link between very vigorous exercise and increased CAC progression warrants further investigation. Researchers propose potential mechanisms that might explain this phenomenon:
Catecholamine Levels: Very vigorous exercise is known to trigger a surge in catecholamine levels, hormones that influence heart rate and blood pressure. Chronically elevated levels of these hormones could increase coronary mechanical stress and disrupt blood flow patterns, potentially promoting atherosclerosis development.
Inflammation: Very vigorous exercise might also induce long-lasting proinflammatory changes in monocytes, immune system cells involved in atherosclerotic plaque formation.
Clinical Relevance:
The presence of CAC and atherosclerotic plaques is a strong predictor of future cardiovascular events in both the general population and patients with existing cardiovascular conditions. While studies, including MARC-2, have documented a higher prevalence and severity of coronary atherosclerosis in athletes compared to non-athletes, athletes generally enjoy a longer lifespan. This apparent contradiction could be attributed to:
Beneficial Adaptations: Exercise training can induce favorable adaptations within the coronary arteries, potentially mitigating the risks associated with increased CAC.
Lower Risk Plaque Morphology: The type of plaque formation observed in athletes might be less prone to causing cardiovascular complications compared to the plaques typically seen in the general population.
Limitations and Future Directions:
The MARC-2 study, while insightful, has limitations. The participants were all male and predominantly White, restricting the generalizability of the findings. Additionally, the potential influence of lifestyle changes prompted by awareness of their initial CAC scores (from MARC-1) cannot be entirely ruled out.
Future research should address these limitations by including a more diverse population and employing longer follow-up periods. Additionally, investigating the specific types of exercise within the vigorous and very vigorous categories could provide valuable insights. Ultimately, research efforts should focus on:
Understanding the CVD Risk: Assessing the actual cardiovascular disease risk associated with the observed increase in CAC due to very vigorous exercise in athletes.
Optimizing Exercise Regimens: Developing exercise recommendations that balance the benefits of exercise with potential risks associated with very vigorous exercise intensity in athletes.
Unforeseen Implications:
The MARC-2 study's findings raise intriguing questions about the ideal exercise intensity for athletes in terms of cardiovascular health. Here's why:
Challenge to Traditional Wisdom: Traditionally, high-intensity exercise has been considered universally beneficial for the heart. However, MARC-2 suggests that very vigorous exercise might be counterproductive for some athletes regarding coronary artery calcification.
Uncertain CVD Risk: While the study observed increased CAC with very vigorous exercise, it remains unclear if this directly translates to a higher risk of cardiovascular events (CVD) like heart attacks or strokes. Further research is needed to establish this connection.
Specificity of Plaque Type: The study also highlights the potential importance of plaque morphology. The type of plaque formation in athletes might be less dangerous than the kind typically seen in the general population. This warrants further investigation.
Optimizing Exercise Regimens for Athletes:
Understanding the interplay between exercise intensity and CAC progression can inform the development of tailored exercise recommendations for athletes. Here are potential considerations:
Individualized Plans: Athletes might benefit from personalized exercise programs that account for factors like age, baseline health status, and exercise preferences while optimizing cardiovascular health.
Intensity Variation: Integrating a mix of exercise intensities, including moderate, vigorous, and perhaps even lower-intensity recovery periods, could be a prudent approach.
Focus on Overall Cardiovascular Health: While CAC is an important marker, a holistic approach to cardiovascular health should be emphasized, including maintaining healthy blood pressure, cholesterol levels, and a balanced diet.
Conclusion:
The MARC-2 study sheds light on the intricate relationship between exercise intensity and coronary artery health in athletes. While vigorous exercise appears to be protective, very vigorous exercise might be linked to faster CAC progression. Future research needs to explore the CVD risk associated with this finding and develop optimal exercise strategies for athletes to maximize cardiovascular health. By understanding these nuances, we can create evidence-based recommendations to help athletes achieve their peak performance while safeguarding their long-term heart health.
Journal reference
Aengevaeren, V. L., Mosterd, A., Bakker, E. A., Braber, T. L., Nathoe, H. M., Sharma, S., Thompson, P. D., Velthuis, B. K., & Eijsvogels, T. M. H. (2023). Exercise Volume Versus Intensity and the Progression of Coronary Atherosclerosis in Middle-Aged and Older Athletes: Findings From the MARC-2 Study. Circulation, 147(13), 993–1003. https://doi.org/10.1161/CIRCULATIONAHA.122.061173
Related
Disclaimer
The information provided in this article is for informational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health care provider with any questions you may have regarding a medical condition or treatment. Never disregard professional medical advice or delay in seeking it because of something you have read in this article.