Born to Run: Study Reveals Genetics, Not Just Grit, Drives Low Heart Rates in Athletes

For decades, sports medicine has operated under a simple premise: if an athlete’s heart beats at a crawl—sometimes fewer than 40 times per minute—it is a “badge of honor” earned through thousands of hours of grueling cardiovascular training. However, groundbreaking research is challenging this “nurture over nature” narrative.

A new study published in the prestigious journal Circulation suggests that the profound bradycardia (slow heart rate) seen in elite endurance athletes may not be a result of training alone. Instead, many of these athletes may be genetically “predestined” for a slow pulse, a trait that might actually give them a head start in the world of competitive sports.

The Genetic Blueprint of the Athletic Heart

The study, led by André La Gerche, MBBS, PhD, from the University of Melbourne, utilized a sophisticated tool called a polygenic risk score to analyze the genetic makeup of 465 endurance athletes. This score aggregates the effects of many small genetic variations known to influence heart rate.

The findings were striking: athletes—particularly those with resting heart rates below 40 beats per minute (bpm)—carried a specific genetic profile that predisposed them to slower heart rates. This genetic signature was significantly more common in athletes than in the general population.

“This raises the possibility that a tendency of low heart rate in athletes may be an inherited trait rather than a fully acquired phenomenon,” Dr. La Gerche noted. He suggested that this turns traditional theories on their head. Rather than athletes merely training their way to a low heart rate, they may be born with a physiology that allows them to excel in endurance disciplines in the first place.

Redefining the “Red Flag”

In a clinical setting, a heart rate below 60 bpm is classified as bradycardia. For the average person, a rate dipping below 40 bpm—the “grey zone”—is often a cause for medical concern, potentially signaling a malfunction in the heart’s electrical system.

However, in the study cohort, these ultra-low rates and even “sinus pauses” (where the heart skips a beat for 2 to 3 seconds) were not only common but well-tolerated.

Key Findings at a Glance:

• The Cohort: 465 endurance athletes were monitored over five years.

• The Difference: Athletes with the lowest heart rates showed “athletic cardiac remodeling”—larger, stronger hearts with excellent pumping function.

• The Outcome: Despite heart rates that would alarm a general practitioner, these athletes experienced no increase in fainting (syncope), dangerous arrhythmias, or adverse health events.

Inherited Edge vs. Medical Malfunction

To understand why this matters, it is essential to distinguish between physiological adaptation and pathological disease.

Dr. Fengwei Zou, a fellow in clinical cardiac electrophysiology at Montefiore Einstein who was not involved in the study, explains that genetic bradycardia in athletes is fundamentally different from the heart issues seen in the general public.

“Genetic bradycardia… represents an inherited tendency toward slower electrical activity that may actually favor endurance performance,” Dr. Zou said. “In contrast, nongenetic bradycardia in the general population is more often acquired and linked to progressive disease in the heart’s electrical system.”

For a non-athlete, a very slow heart rate can lead to decreased blood flow to the brain, causing dizziness, fatigue, or lethargy. For the athlete, it appears to be a benign, and perhaps advantageous, part of their biological makeup.

Public Health Implications: A Move Toward Precision Medicine

This research has significant implications for how doctors treat both athletes and the general public.

1. Avoiding Unnecessary Intervention: Understanding that an athlete’s low heart rate is a combination of genetics and fitness can prevent unnecessary medical tests or the implantation of pacemakers in healthy individuals.

2. Rethinking Athletic Potential: The study suggests that certain people may be “genetically primed” for endurance. This could eventually change how talent is identified in youth sports, though it also raises ethical questions about genetic screening in athletics.

3. Screening Efficiency: By using polygenic risk scores, clinicians might one day be able to better distinguish between an athlete with a healthy, slow heart and a patient who is developing a genuine heart block.

Limitations and Future Outlook

While the results are compelling, the researchers emphasize that genetics is not the only factor. Dr. La Gerche noted that “both fitness and genetic variation contribute” to how the heart functions. The study was also focused on endurance athletes; it remains to be seen how these genetic markers manifest in sprinters or power athletes.

Furthermore, while the five-year follow-up showed no adverse effects, longer-term studies are needed to ensure that these genetically slow heart rates remain benign as athletes age into their 70s and 80s.

“This unexpected finding is certain to provoke further research and inquiry,” Dr. La Gerche concluded. For now, it seems that for the world’s best marathoners and cyclists, greatness might truly be written in their DNA.

Reference Section

• https://www.medscape.com/viewarticle/endurance-athletes-may-harbor-genetic-predisposition-2026a10001j8

Medical Disclaimer: This article is for informational purposes only and should not be considered medical advice. Always consult with qualified healthcare professionals before making any health-related decisions or changes to your treatment plan. The information presented here is based on current research and expert opinions, which may evolve as new evidence emerges.