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When “Healthy” Habits Can Slowly Kill You

Authored by Janen Khan

Art by Kaylah Nicholson

Engaging in physical activity is undoubtedly an important part of lowering the risk of disease - but it does not directly translate to “good health”. Contrary to the claims of rising fitness influencers preaching intense exercise for achieving immediate results, new studies are emerging on how vigorous exercise can sometimes do more harm than good. 

Whether it is training for weight loss, muscle growth, or general health maintenance, the fitness industry is experiencing a sudden boom in its members as the number of people becoming physically active is increasing post-pandemic. Without doing much research, many jump into the workout “regimens” circulated around social media and fitness gurus. What many do not realize is that some high-intensity workouts can actually accelerate their risk of disease, specifically cardiovascular disease. 

Cardiovascular disease (CVD) encompasses several heart and blood vessel diseases that are often accompanied by irregular heartbeats, shortness of breath, and fatigue. A key marker of CVD includes atherosclerosis, the thickening or hardening of the arteries caused by a buildup of plaque in the inner lining of an artery [1]. The buildup of plaque reduces blood flow and oxygen supply to body organs, leading to complications such as heart attacks, tissue failure, and even death. Physical activity has traditionally been associated with a  significantly lower risk of  CVD and heart failure events,  with an average  30%  to  40%  risk reduction for the most active individuals [2]. However, researchers at the American College of Cardiology are finding evidence that suggests exercising at very vigorous intensities can accelerate coronary artery calcification (CAC) and plaque calcification. Thus, it becomes of interest to study the longitudinal relationship between exercise training characteristics and coronary atherosclerosis, especially for those exercising in hopes of improving their heart health [3]. 

In order to test the conundrum, they investigated the progression of coronary  atherosclerosis in  289  middle-aged and older male athletes using  CAC  scoring and coronary CT angiography (CCTA) to assess its association with exercise characteristics over a period of 6.3 years [4]. The prevalence and severity of CAC and plaques were revealed by imaging from CCTA. The researchers assigned relative intensities to the workout regimens by using their respective metabolic equivalent of task (MET), a ratio that estimates the amount of energy used by the body during physical activities relative to the resting state. For reference, a score of 1 MET refers to the amount of energy used to sit down quietly. The volume (metabolic equivalent of task [MET] hours/week) and intensity (moderate [3-6 MET hours/week]; vigorous [6-9 MET hours/week]; and very vigorous [≥9 MET hours/week]) of exercise training were quantified during follow-up [4]. They predicted that higher volume and intensity exercise would be associated with the greatest increase in the risk of coronary atherosclerosis: the higher the CAC score, the more likely one is to develop heart disease or experience a negative episode such as a heart attack or stroke.

In the follow-up of the cohort, the prevalence of CAC increased from a baseline of 52% to 71% and the median CAC score increased from a baseline of 1 to 31 [4]. The researchers did not observe a correlation between exercise volume and changes in CAC or plaque, but it is still possible that exercise volume can be involved in initiating coronary atherosclerosis but not in its progression. Vigorous-intensity exercise was associated with a smaller increase in CAC score, whereas very vigorous-intensity exercise was associated with a greater increase in CAC score. Very vigorous exercise was also associated with increased odds of increased calcified plaques [4]. The authors attribute the increased calcification to higher catecholamine levels in athletes who participate in higher-intensity workouts. As the neurohormone’s level rises with the rigorousness of exercise, it results in an increase in heart rate and blood pressure. The subsequent coronary mechanical stress is sufficient enough to accelerate atherosclerosis [5].

Overall, although CAC progression occurred both in those exercising vigorously and  very vigorously, vigorous exercise was associated with modest progression, and very vigorous exercise was associated with accelerated progression. Coronary plaque is the main underlying precursor to atherosclerotic cardiovascular disease events, making it vital to further investigate the clinical implications of one's "healthy" habits to lower the risk of ailments and improve the quality of life. 

Works Cited

[1] Eijsvogels, T. M. H., Molossi, S. (2016). Exercise at the extremes. Journal of the American College of Cardiology, 67(3), 316–329.

[2] Atherosclerosis. Atherosclerosis | Johns Hopkins Medicine.

[3] Aengevaeren, V. L., Mosterd, A. (2023). Exercise volume versus intensity and the progression of coronary atherosclerosis in middle-aged and older athletes: Findings from the MARC-2 Study. Circulation.\

[5] Shah, A. B., Bechis, M. Z. (2019). Catecholamine response to exercise in patients with non-obstructive hypertrophic cardiomyopathy. The Journal of Physiology, 597(5), 1337–1346. 

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