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Society has come a long way in recognizing women’s strength. No longer considered the “weaker sex,” women not only bring life into the world and hold prominent positions in previously male-dominated industries, but also hold world titles in the Olympics and endurance sports. In other words, women push themselves beyond their limits just like men.

Yet, despite this surge in female athletic participation, women still haven’t achieved equality when it comes to doctors’ understanding of and caring for their hearts. Women have been under-represented in cardiac health research, including the female heart’s adaptation to endurance training and its potential consequences. Recent small-scale studies suggest that there are, in fact, important cardiac differences between the sexes.

Cardiologists advise anyone who participates in marathons, triathlons, and high-intensity interval training (HIIT) to make sure their bodies are prepared for endurance events to avoid any short-term or long-term cardiac events.

Sudden Cardiac Death in Female Endurance Athletes

Sudden cardiac death (SCD) during athletic competition remains a rare occurrence, affecting more men than women. In fact, a woman’s risk of SCD during endurance sports is estimated to be around 10 times lower than for her male colleagues.

The most common causes of SCD are generally driven by age rather than sex. Athletes under age 35 — both men and women alike — are susceptible to genetically inherited structural heart problems, including hypertrophic cardiomyopathy (HCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC), as well as potentially lethal heart rhythm problems called “channelopathies.”

Over age 35, coronary artery disease becomes the most prevalent condition, with women receiving some protection from their higher estrogen levels until they reach menopause.

Hormonal and Biological Protection for Women

Several theories might explain why women appear to be more protected from SCD during intense competition. Male physiology is observed to be wound more tightly, meaning that a man’s arteries and blood vessels tend to constrict more during intense activity and stressful situations than a woman’s. The increased blood pressure, coupled with an outpouring of adrenaline during competition, places a strain on the heart. This additional strain may trigger dangerous rhythm problems — generally in those with underlying, inherited cardiac problems from long-term training.

Another possible explanation relates to obvious hormonal differences between men and women. Clinically, testosterone promotes thickening of the heart muscle, which may explain why men are more susceptible than women in developing complications from diseases like cardiomyopathy.

Estrogens, on the other hand, are protective in this regard, and delay that same process of heart muscle thickening. Estrogen generally protects women from developing coronary artery disease (CAD) at young ages, but the risk rises as they reach menopause.

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Screening for Potential Cardiac Problems

Screening programs identify potential cardiac risks in individuals who show no outward symptoms of heart problems. They typically involve a comprehensive medical history review, focused physical examination, and sometimes an electrocardiogram (ECG). Men exhibit changes in their ECG patterns more often than women, and these variations are usually considered normal and purely the result of physiologic adaptation to training. On the other hand, women are less likely to stray from normal parameters, so most ECG changes are cause for concern and more likely represent a real heart problem.

Consistent endurance training induces physiologic adaptations to the heart. Cyclists, for example, often sustain elevated heart rates for extended periods of time during two distinct types of high-cardiac-output workouts known as dynamic and static stressors. The combination results in a generally increased cardiac mass. Due to their higher estrogen levels, women tend to adapt to exercise in a qualitatively similar manner, but quantitatively different than men, showing only minimal heart enlargement and virtually no heart wall thickening.

Know the Warning Signs

Symptoms of heart problems vary in women and men.

Women are less likely to experience classic chest pain due to a heart problem, but may report more subtle symptoms, such as indigestion, heartburn, fatigue, or poor exercise performance. Additionally, in young women, these symptoms often are incorrectly blamed on menstrual problems, eating disorders, iron deficiency anemia, pregnancy, or thyroid disease.

It is the woman’s primary care provider who must know enough to exclude these other conditions to diagnose a potential heart problem and then make an appropriate referral to a cardiologist.

Prolonged endurance training in young women also can lead to menstrual irregularities resulting in the same kind of reduced estrogen levels typically seen in older postmenopausal women. These athletes should be evaluated for traditional cardiac risk factors such as high blood pressure, cholesterol problems, and diabetes, with appropriate intervention to modify their risk.

Long-Term Effects of Endurance Training in Women

Regular exercise is the cornerstone of prevention and treatment for many cardiac and noncardiac diseases; however, some researchers suggest that the too much exercise may be detrimental to the athlete’s health and viewed as having an “overdosing” effect.

The biological adaptation to handle the stress of pregnancy may be a key reason for female adaptation to endurance training. Recent research has highlighted that, during pregnancy, the body functions at a basal metabolic rate of 2.2 times the normal – burning up to 4,000 calories per day. Extended over a period of 40 weeks, pregnancy essentially can be considered the ultimate endurance event — a true test on the limits of human performance.

Despite the substantially lower risk of SCD in women, cardiac risk screening of female endurance athletes and at-risk pregnant women is important and should be carried out by clinicians familiar with the differences in the physiology between men and women. As the current generation of elite female athletes matures into tomorrow’s master champions, we will undoubtedly learn a great deal more about the long-term cardiac implications of endurance training in women.

About Heart and Vascular Institute

The UPMC Heart and Vascular Institute has long been a leader in cardiovascular care, with a rich history in clinical research and innovation. As one of the first heart transplant centers in the country and as the developer of one of the first heart-assist devices, UPMC has contributed to advancing the field of cardiovascular medicine.