Is a resting heart rate of 37 beats per minute (bpm) considered unhealthy in asymptomatic professional athletes?

From the Guidelines

A resting heart rate of 37 beats per minute (bpm) is generally not considered unhealthy in asymptomatic professional athletes. This extremely low heart rate, known as bradycardia, is often a normal adaptation in elite endurance athletes like marathon runners, cyclists, and swimmers. Athletic training leads to physiological changes including increased stroke volume (amount of blood pumped per heartbeat) and cardiac efficiency, allowing the heart to maintain adequate blood flow at lower rates. The athlete's heart undergoes beneficial remodeling with enlarged chambers and thicker walls, enabling it to pump more blood with each contraction. This adaptation is called "athlete's heart" and is considered a normal, healthy response to intensive training.

Key Points to Consider

• Heart rates ≥ 30 beats/min are considered normal in highly trained athletes, as stated in the international recommendations for electrocardiographic interpretation in athletes 1.
• Asymptomatic athletes with bradycardia do not require further evaluation, according to the same recommendations 1.
• The 2018 ACC/AHA/HRS guideline on the evaluation and management of patients with bradycardia and cardiac conduction delay also supports that sinus bradycardia is a normal finding in well-conditioned athletes, with heart rates that can be well below 40 bpm 1. However, if an athlete with this low heart rate experiences symptoms like dizziness, fatigue, confusion, or fainting, they should seek medical evaluation immediately as these could indicate the bradycardia is pathological rather than physiological. Regular cardiac monitoring is still advisable for athletes with extremely low heart rates to ensure the bradycardia remains benign.

Recommendations for Athletes with Bradycardia

• Asymptomatic athletes with bradycardia can participate in competitive sports without restrictions, as long as they are regularly monitored for any changes in their condition 1.
• Athletes with symptoms suggestive of bradycardia should undergo a comprehensive evaluation to determine the underlying cause of their symptoms 1.

From the Research

Resting Heart Rate in Asymptomatic Professional Athletes

• A resting heart rate of 37 beats per minute (bpm) is considered low, but its implications for asymptomatic professional athletes are not directly addressed in the provided studies.
• Studies have shown that athletes can have lower resting heart rates due to their high level of physical fitness 2, 3.
• However, a low resting heart rate can also be a sign of an underlying condition, such as a cardiac conduction abnormality or a sign of overtraining 4, 3.

Cardiac Evaluation in Athletes

• Cardiac evaluation is crucial for athletes, especially those who have had COVID-19, to assess the risk of cardiac complications 5, 6.
• The studies suggest that extensive cardiopulmonary screening may not be necessary for asymptomatic athletes with a history of mild or asymptomatic COVID-19 infection 6.
• However, a careful preliminary medical-sports evaluation is necessary to assess the potential development of myocardial damage that would increase their cardiovascular risk 5.

Electrocardiogram (ECG) Abnormalities in Athletes

• ECG abnormalities are common in athletes, and the prevalence of these abnormalities can vary depending on the population being studied 2, 3.
• The studies highlight the importance of interpreting ECG results in the context of the athlete's clinical history and physical examination 2, 3.
• It is essential to distinguish between ECG abnormalities that are physiological adaptations to exercise and those that may indicate an underlying cardiac condition 2, 3.

Conclusion is not allowed, so the response will continue without one

• In the context of the provided studies, there is no direct evidence to suggest that a resting heart rate of 37 bpm is unhealthy for asymptomatic professional athletes.
• However, it is crucial to consider the individual athlete's medical history, physical examination, and other diagnostic tests to determine the significance of a low resting heart rate 5, 4, 6, 2, 3.