The previous ideology was that endurance exercise can protect the heart from damage. However, current research shows the protective factor of endurance exercise may not be true. With the growing popularity of endurance and ultra-endurance sports, finding the connections between endurance exercise and heart damage is crucial. While regular exercise improves various health parameters and increases life expectancy, cardio, and endurance enthusiasts are not immune to heart disease.
Endurance training and the heart
New research suggests that endurance and ultra-endurance athletes can be at risk for heart damage. Excessive endurance exercise appears to be a risk factor for increased coronary plaques.1,2 Lifelong endurance athletes have more coronary plaques than an average healthy individual.1 In other words, healthy non-athletes had fewer coronary plaques.
A 2023 study compared the heart health of a control group of males versus lifelong and late-onset male athletes (starting after age 30).1 The athletes were mostly cyclists, followed by smaller groups of runners and triathletes. Most of the control group exercised for three hours or less per week. The control group’s exercise was primarily running, and other non-endurance activities and some of the control group did not exercise regularly.
The lifelong and late-onset male athletes performed around 10 to 11 hours per week of endurance exercise. The lifelong athletes also had a greater incidence of coronary artery stenosis. All groups had similar blood pressure, cholesterol, and blood glucose levels, but the control group had higher body weights, BMIs, and body fat percentages.
A 2016 study also suggests that while regular physical activity has been associated with lower mortality, there is an exercise threshold where mortality risks increase.2 Some of the risk factors and damage from years of endurance training are
- myocardial fibrosis,
- atrial fibrillation (AF),
- ventricular arrhythmias,
- and coronary artery calcification.2
Parts of the heart affected by endurance exercise
Excessive endurance exercise affects multiple areas of the heart including, the atria and ventricles. With dysfunction of the heart tissues, blood, oxygen, and nutrient flow throughout the body will be negatively affected. The damage that long-term endurance exercise can lead to are:
- impaired function of the right ventricle,
- dilation of the left atrium,
- right ventricle arrhythmias,
- atrial fibrillation,
- and atrial flutter.2
Can heart damage be reversed?
In the 2016 study, animals (rats) were the subjects of a 16-week vigorous running program to test for a relationship between endurance exercise and heart damage. The rats developed left ventricular hypertrophy, diastolic dysfunction, and atrial dilation.2 These cardiac problems were reversed back to the heart’s original state after eight weeks of detraining.2 Although the reversal was seen in rats, the possibility may exist that a similar response could be seen in humans.
How much exercise is enough?
It is without a doubt that exercise has health and longevity benefits. Still, it is the dose and type that are questionable. Participants who exercised for 15 minutes per day had a 14% reduced risk of all-cause mortality and a three-year increase in life expectancy.2 Every 15 minutes beyond the minimum amount further reduced all-cause mortality by 4%.2
More than 100 minutes of moderate exercise or 50 to 60 minutes per day of strenuous exercise offered no additional health benefits. The Copenhagen Heart Study3 also showed the optimal amount of jogging was two to three times per week at a slow or average pace. Interestingly, those jogging at a strenuous pace did not experience a mortality rate much different from sedentary individuals.2
Lifelong endurance exercise and sports participants do not get additional protection against coronary artery calcifications compared to those who live an active healthy lifestyle.1 In contrast, lifelong middle-aged endurance and ultra-endurance male athletes had more coronary plaques.1 More longitudinal research is needed to understand the contradiction between heart health and cardiovascular exercise. Nevertheless, it is reasonable to say that exercise is good, but excessive exercise is likely unsafe.
- De Bosscher R, Dausin C, Claus P, Bogaert J, Dymarkowski S, Goetschalckx K, Ghekiere O, Van De Heyning CM, Van Herck P, Paelinck B, El Addouli H. Lifelong endurance exercise and its relation with coronary atherosclerosis. European Heart Journal. 2023;152. https://doi.org/10.1093/eurheartj/ehad152
- Lee AK, Morrison B, Isserow SH, Heilbron B, Krahn AD. The impact of excessive endurance exercise on the heart. British Columbia Medical Journal. 2016;58(4):203-9. https://bcmj.org/articles/impact-excessive-endurance-exercise-heart
- The Copenhagen City Heart Study – Full Text View. ClinicalTrials.gov. https://clinicaltrials.gov/ct2/show/NCT02993172. Published December 15, 2016.