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With the Paris Olympics underway, Medicine.net provides you with more medical knowledge.

Exercise is one of the most cost-effective investments individuals can make in their health. Various epidemiological studies have shown that cardiovascular disease incidence rates are reduced by 40%-50% among those who are enthusiastic about physical exercise. While exercise indeed improves many aspects of the human body, a study published in NEJM Evidence highlights another possibility: the potential adverse effects of excessive exercise on the heart.

The article indicates that as the amount of exercise increases, the rate of risk reduction gradually diminishes. At extremely high levels of physical activity, the risk may stabilize or even increase. It points out that prolonged and intense aerobic exercise can lead to several heart issues, including myocardial cell damage, myocardial fibrosis, arrhythmias, and aortic dilation.

Myocardial Damage and Biomarkers–Following intense aerobic exercise, such as a marathon, athletes often show elevated levels of cardiac troponin, a biomarker associated with heart risk. The increase in troponin levels is related to myocardial cell damage. Although marathon running is a form of prolonged, intense aerobic exercise, and elevated troponin levels post-exercise do not necessarily result in severe adverse outcomes, consistently high levels of troponin over time could have different implications.

Myocardial Fibrosis and Coronary Artery Calcification–Gadolinium-enhanced cardiac magnetic resonance imaging (cMRI) has revealed increased myocardial fibrosis and coronary artery calcification in endurance athletes. Although the clinical significance of these changes remains uncertain, they may be critically important for patients with arrhythmogenic right ventricular cardiomyopathy.

Atrial Fibrillation–The relationship between exercise and atrial fibrillation (AF) is complex, with research suggesting a U-shaped curve between activity levels and AF risk. The authors of the article propose that increased parasympathetic and sympathetic tone, along with inflammation, may be key factors in exercise-induced AF, though these factors have not been definitively confirmed.

Aortic Dilation–While there is no significant change in the aortic diameter of young athletes, some studies have found notable aortic dilation in retired athletes. This finding warrants attention, even though it does not conclusively prove a direct link to prolonged intense aerobic exercise.

Most of the research discussed in the article pertains to athletes, primarily because they often engage in intense aerobic exercise for extended periods during competitions. Some may argue that athletes' bodies differ significantly from those of the general population; however, these differences are not substantial enough to undermine the research findings.

While moderate exercise can reduce cardiovascular disease risk, excessive exercise may not only fail to lower this risk but also potentially lead to a range of heart problems. These findings serve as a reminder to everyone that exercise intensity and duration require careful consideration. Clinicians should be aware of these potential training effects induced by exercise and advise patients accordingly.

Reference:

Thompson PD, Eijsvogels TMH, Kim JH. Can the Heart Get an Overuse Sports Injury? NEJM Evid. 2023 Jan;2(1):EVIDra2200175. doi: 10.1056/EVIDra2200175. Epub 2022 Dec 27. PMID: 38320102.