Athletic Heart Syndrome


Athletic heart syndrome is the adaptation of an athlete's heart in response to the physiologic stresses of strenuous physical training. It can be difficult to distinguish a significant medical condition from an athletic heart. Athletic heart syndrome is also known as athlete's heart, or athletic bradycardia.


In athletic heart syndrome, the heart becomes enlarged due to intense, consistent, and prolonged amounts of exercise over long periods of time. In general, it is seen in athletes whose exercise regimen includes heavy weight training or in those who exercise more than an hour each day.

Athletic heart syndrome is thought to be a benign condition; however, it is important to distinguish it from other, more serious heart disorders. An athlete with an undiagnosed cardiac condition could suffer sudden unexpected death (SUD), typically during or shortly after physical activity. Often there is no indication that someone is at risk for SUD, although in some cases warning signs (such as chest pain or dizziness) appear that cause the person to seek medical advice. It is important to note that SUD occurring during physical activity may not be caused by athletic heart syndrome but by an undiagnosed congenital heart disorder.

Cardiac output—
Amount of blood that leaves the heart per heartbeat.
Thickening of the muscle walls of the heart.
Positron emission tomography (PET) scan—
A noninvasive scanning technique that utilizes small amounts of radioactive positrons (positively charged particles) tovisualize bodyfunction and metabolism.
Sinus bradycardia—
A heart rate of less than 60 beats per minute while at rest.
Sudden unexpected death.


Athletic heart syndrome is common in athletes, but the exact incidence is not known. Estimates of the yearly rate for occurrence of SUD vary due to study methodology, but recent data indicate an incident rate of 2.3 to 4.4 per 100,000 deaths. SUD is more common in male athletes and those of African/Afro-Caribbean ethnicity and among basketball and football players.

Causes and symptoms

Effect of fitness and exercise

Individuals with athletic heart syndrome do not generally display symptoms other than a consistently low heart rate (bradycardia) while at rest (resting heart rate). This low heart rate may be found during a routine medical exam, prompting clinicians to suggest tests to determine the size and performance of the heart.


Changes in heartbeat are detectable on an electrocardiogram (ECG or EKG). The size of the heart may be determined by an echocardiogram (also known as cardiac ultrasound). Functional changes of the heart may be assessed by doing a positron emission tomography (PET) scan. Many of the changes seen in athletic heart syndrome mimic those of various heart diseases. Careful examination must be made to distinguish heart disease from athletic heart syndrome. In some cases three months of deconditioning may be advised to make a definitive diagnosis.


No treatment is required for individuals who have athletic heart syndrome. With cessation of strenuous, prolonged training, most heart-related changes associated with athletic heart syndrome will return to pretraining condition within a few months.


Athletic heart syndrome is the consequence of a normal adaptation by the heart to increased physical activity. The changes in the electrical conduction system of the heart may be pronounced and diagnostic, but are not usually problematic in healthy, fit individuals. In the case of SUD, other heart problems are involved. In 85%–97% of SUD cases, an underlying structural defect of the heart has been noted.


Individuals may choose to limit the amount and degree of strenuous exercise training to prevent athletic heart syndrome.

See also Electrocardiogram ; Weightlifting .




Benson, Roy, and Declan Connolly. Heart Rate Training. Champaign: Human Kinetics, 2011.

Corbin, Charles B., and Ruth Lindsey. Fitness for Life. 5th ed. Champaign: Human Kinetics, 2007.

Katch, Victor L., William D. McArdle, and Frank I. Katch. Essentials of Exercise Physiology. Philadelphia: Lippincott Williams & Wilkins Health, 2011.

Sutton, Amy L. Fitness and Exercise Sourcebook. 3rd ed. Detroit: Omnigraphics, 2007.


Chandra, Navin, et al. “Sudden Cardiac Death in Young Athletes: Practical Challenges and Diagnostic Dilemmas.” Journal of the American College of Cardiology 61, no. 10 (March 2013): 1027–40.


McKelvie, Robert S. “Athlete's Heart.” Merck. (accessed March 1, 2017).


American Council on Exercise, 4851 Paramount Dr., San Diego, CA, 92123, (858) 576-6500, (888) 825-3636, ext. 782, Fax: (858) 576-6564, .

American Heart Association (AHA), 7272 Greenville Ave., Dallas, TX, 75231, (800) 242-8721, .

National Athletic Trainers' Association, 1620 Valwood Parkway, Suite 115, Carrollton, TX, 75006, (214) 637-6282, Fax: (214) 637-2206, .

National Institutes of Health (NIH), 9000 Rockville Pike, Bethesda, MD, 20892, (301) 496-4000, .

US National Library of Medicine, 8600 Rockville Pike, Bethesda, MD, 20894, (888) 346-3656, .

John T. Lohr, PhD
Revised by Laura Jean Cataldo, RN, EdD

  This information is not a tool for self-diagnosis or a substitute for professional care.