The Heart of a Trained Athlete: Does Excessive Training Risk Cardiovascular Health?

Could athletes who train too hard potentially have a higher risk of heart problems than recreational athletes?

There’s no doubt that exercising on a regular basis is good for your health, as it helps control weight, combats a wide range of health conditions, and promotes better sleep, among countless other benefits. When it comes to the heart, exercise greatly improves cardiovascular function and can even lower some heart disease risk factors. The heart of a trained athlete who routinely exercises more than an hour a day even looks and performs differently than the heart of someone who never exercises. But could athletes who train too hard potentially have a higher risk of heart problems than recreational athletes?

Athlete’s Heart

Like all muscles in the body, the heart gets stronger with exercise, allowing it to pump more blood through the body with each beat and continue to work at an optimal rate with less strain. In fact, the heart of a trained athlete can grow to be larger than normal, so large that it may resemble the heart of someone with cardiovascular disease. This is called athlete’s heart, a condition generally regarded as a benign physiological adaptation to intense training; however, there is an ongoing debate about whether it is truly benign or if it is harmful to an athlete’s health. Swedish physician Skilanglauf Henschen is credited with the first description of the condition in 1899 after he examined the hearts of cross-country skiers. He concluded that dilatation and hypertrophy were present in both the left and right sides of the heart, but that these changes were favorable, noting than an enlarged heart “can perform much more work than a normal heart.” However, others believed the heart of a trained athlete to be weakened due to the strain created by excessive training and that athletes were susceptible to deteriorating cardiac function and heart failure.

One study published in the Journal of the American College of Cardiology found that athletes with larger hearts may have decreased heart function. Data revealed that 11.6% of Tour de France cyclists with enlarged hearts had a reduced ejection fraction, or the percentage of blood ejected from the heart with each beat. A normal left ventriular ejection fraction (LVEF) is about 55%-70%, whereas the cyclists’ LVEFs were less than 52%. Another study conducted by the American Heart Association produced similar results. However, there are numerous factors that could have affected these results, including the fact that athletes tend to have lower heart rates and higher blood volume. Also, the formulas used to calculate ejection fraction are designed for normal-sized hearts, making it possible that an enlarged heart may have caused a “mathematical underestimation.” Finally, it is possible that performance-enhancing drugs (PEDs) may have affected the results as well. In one study of athletes’ hearts, 71% of former professional cyclists admitted to using PEDs during their careers.

In many cases, athletes’ hearts revert to their original state after only 8 to 12 weeks of no training, and even shrink between seasons when they reduce their training routine and rest. It is unlikely that this would happen if heart disease were present. Athletes with more advanced athlete’s heart, however, are an exception, as their hearts mostly regress, but do not completely reverse even years after they stop training.

Arrhythmia

Excessive endurance training can also cause abnormal heart rhythms that span from benign, which can be resolved with prescribed rest, to malignant. A Swedish study conducted at Uppsala University found that trained athletes have a higher risk of heart rhythm problems than those who train less. The study examined data from 47,000 cross-country skiers between 1989 and 1998 who participated in a 56-mile race that takes place in Sweden every March. The participants ranged from trained athletes to recreational skiers. Researchers found that those who had completed the race 7 or more times had a 29% higher risk of developing heart arrhythmia than those who had only completed the race once. Furthermore, trained athletes who finished the race within 1.6 times the winning time had a 37% higher risk of arrhythmia than recreational athletes who finished in more than 2.4 times the winning time.

Atrial Fibrillation

The most common heart rhythm problem is atrial fibrillation, which occurs when rapid electrical signals cause the heart’s 2 upper chambers to contract fast and irregularly. Many studies have shown a relationship between high-endurance training and atrial fibrillation. High-endurance training causes the left atrium of the heart to enlarge, and because atrial fibrillation originates from the left atrium in 90% of cases, it is thought that left atrial enlargement is one of the reasons athletes have an increased risk of atrial fibrillation. In a study of almost 300 athletes, researchers found that endurance sport training increased the probability of suffering from atrial fibrillation between 2 and 10 times.

Whereas the accepted benefits of exercise on cardiovascular health remain numerous, it is without a doubt that excessive training can lead to heart complications later in life. Our bodies, even those of athletes, have their limits.

Reference

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