Heart Health for Endurance Athletes: Screening, the Athlete's Heart and Red Flags

If you train hard and often, you should know your heart — not out of fear, but out of precision. Most endurance athletes have a healthy, well-adapted "athlete's heart"; a small minority carries silent risks that only show up under maximal exertion. This article explains what is normal in an athlete's heart, which screening examinations make sense before competitions, and which warning signs you should never ignore during training.

Why this topic matters more for endurance athletes than for anyone else

A trained endurance athlete's heart works differently from an untrained one — and that is precisely why standard reference values are often confusing. Years of volume training enlarge the heart chambers, thicken the myocardium and drop resting heart rate to levels that would signal an emergency in a sedentary person. This adaptation is healthy, reversible and benign: the medical term is "athlete's heart".

The problem: a small percentage of athletes carry undiagnosed cardiac disease — hypertrophic cardiomyopathy, arrhythmias, valve defects or congenital coronary anomalies — which can cause sudden cardiac arrest under exertion. These conditions are rare (in athletes over 35 the most common cause is atherosclerosis; in younger athletes, structural anomalies), but they are the leading cause of sudden death during sport.

That is exactly why the rule is: screening is not a sign of weakness — it is part of professional training. If you know your heart is healthy, you also train with more mental freedom and can call on intensity without background noise.

What defines the athlete's heart — and what is normal

Resting heart rate in trained endurance athletes commonly sits between 40 and 60 beats per minute; elite athletes with 10+ weekly training hours sometimes measure 35–40. This is not illness but increased parasympathetic tone and a larger stroke volume: fewer beats pump the same amount of blood. A heart murmur on auscultation can also be benign in athletes — an echocardiogram provides clarity.

The ECG has its typical "athlete patterns" too, which would raise alarms in untrained people: sinus bradycardia, first-degree AV block, isolated voltage criteria for left ventricular hypertrophy, incomplete right bundle branch block, early repolarisation. According to international recommendations (such as the Seattle Criteria), these patterns in athletes are a consequence of training — not pathology. Importantly: marked ST-segment changes, T-wave inversions, pathological Q waves, QT prolongation or ventricular arrhythmias are no longer "athlete's ECG" findings and must be investigated.

The rhythm itself is also allowed to be quiet: in endurance-trained athletes, sinus pauses or isolated extrasystoles occur that appear at rest and disappear under exertion. What matters is the exercise test finding: extrasystoles that INCREASE with exertion are the opposite of benign — a cardiologist should evaluate those.

Screening examinations: what makes sense and when

The baseline for newcomers and competitive athletes: a sports-medicine check-up before the season — medical history, physical examination, resting ECG. That is the minimum level any sports-medicine oriented physician offers.

Useful tiers of screening:

• Resting ECG: for everyone — inexpensive, quick, and it catches rhythm and repolarisation disorders that history-taking misses.
• Exercise ECG (stress test): for beginners over 35 or athletes returning after a long break, ideally before their first race.
• Echocardiogram: measures wall thickness, valves and pumping function — the standard tool to distinguish athlete's heart from cardiomyopathy.
• Lactate/VO2max testing: not cardiac diagnostics, but it delivers your training zones (see our articles on VO2max testing and heart rate zones) — and an exercise ECG can be combined with such performance testing.
• Coronary CT from about 45: for men over 45 and women over 55 with risk factors, coronary CT angiography (CCTA) is increasingly recommended before a marathon or long-distance race. Coronary artery calcium (CAC) is a strong predictor of coronary events in marathon runners.

Timing: the check-up belongs in your base phase — not in race week, where an unexpected finding triggers panic right in the taper. Ideally book it 4–8 weeks before your A-race so there is time for follow-up if needed.

Your own history: answer these questions honestly first

Before you even book an appointment, you can work through the most important risk questions yourself — the international pre-participation screenings (such as the AHA/ESC questionnaires) ask exactly this:

• Exertional symptoms: chest pain, dizziness, unusual shortness of breath or fainting during or immediately after exercise — even once in the last 12 months?
• Family history: sudden or unexplained death of a relative under 50, heart surgery at a young age, a known inherited heart muscle or rhythm disorder?
• Resting findings: heart murmur, unusually high blood pressure, a previously abnormal resting ECG?
• Unexplained performance decline: form dropping for weeks despite correct training — usually a training problem, but occasionally the first symptom (see our article on overtraining symptoms for how to tell the two apart).

Two or more "yes" answers — or a single clear warning symptom — are a clear case for cardiological evaluation before your next hard session. For season planning with a healthy heart, our article on periodization shows how to structure the workload sensibly.

The red flags you should never ignore

Some sensations during training are "normal" — heavy legs from fatigue, the familiar muscle burn during intervals, breathlessness in a final rep. Others never are. These signals should be evaluated immediately:

• Chest pain during exertion — whether pressing, stabbing or burning. Angina can present atypically in athletes; every newly occurring chest pain under load must be investigated until proven harmless.
• Syncope during exertion. Fainting during exercise is never "just circulation" — exertional syncope is one of the classic harbingers of dangerous rhythm events. Stop training and see a cardiologist.
• Racing heartbeat or stumbling beats that don't settle within seconds. Brief bursts of extrasystoles are familiar to almost every athlete; sustained, irregular racing heartbeat over minutes under load belongs in a cardiologist's office.
• Shortness of breath out of proportion to the effort — clearly above your usual level at easy intensity, or with an orthopnoeic character (breathlessness when lying flat).
• New palpitations at rest, especially at night: atrial fibrillation occurs more frequently in endurance athletes with high lifetime training loads than in the general population — and it responds well to treatment when caught early.
• Family events during your training life: if a close relative dies suddenly, that is a reason to talk to your doctor — regardless of how untroubled your own symptoms are.

A word of perspective: this list is not meant to feed hypochondria. The probability that any single signal hides a truly dangerous condition is small. But the only sensible response to a small, serious risk is one clarifying examination — not explaining it away.

Training heart-healthy: the practical rules

Beyond screening, a few behavioural rules measurably lower cardiac risk in training:

• Do not train sick. Fever or viral infections shift the thresholds: exercising with fever can, in rare cases, trigger or aggravate myocarditis (heart muscle inflammation) — the classic "three-day rule" (no hard training until three days after the fever has gone) is a sensible standard. Details in our article on exercising with a cold.
• Progression with restraint. Most cardiac incidents in ambitious recreational athletes happen during or after phases of disproportionate volume or intensity jumps. The 10-percent rule and the ACWR logic (in our article on training load) apply to the heart as well.
• Take heat and thirst seriously. Dehydration and overheating raise heart rate at the same power output and put extra strain on the heart — especially in long races. Our articles on hydration and heat training cover the details.
• Balance caffeine, nicotine and alcohol honestly. High caffeine doses right before intense sessions raise heart rate and blood pressure; regular alcohol is a well-known trigger of atrial fibrillation in endurance athletes. More in our article on alcohol in endurance sports.

How Peakora keeps an eye on your heart signals

Peakora is of course not medical software — but the numbers the app tracks are exactly those cardiologists use as early indicators. The recovery monitor logs resting heart rate, HRV and sleep daily — a sustained rise in resting heart rate over several days surfaces in your data before you even notice it yourself. The plan engine's weekly rhythm prevents intensity and volume from ballooning at the same time — the biggest avoidable cardiac risk factor in recreational sport. And the form trend (TSB) makes visible whether your tiredness is objectively justified or your performance is declining systematically — the moment when a medical check-up also makes sense.

Frequently asked questions about heart health in endurance sport

Which screening tests make sense for endurance athletes?

The foundation is a medical history review, physical examination and a resting ECG. For beginners over 35 or athletes returning after a long break, an exercise ECG is added; an echocardiogram distinguishes the athlete's heart from cardiomyopathy. For men over 45 and women over 55 with risk factors, a coronary CT (CAC/CCTA) is increasingly recommended before marathons or long-distance events.

Which symptoms during training need immediate medical attention?

Chest pain during exertion, fainting while exercising, sustained irregular racing heartbeat, shortness of breath that is out of proportion to the effort, and new palpitations at rest at night. These signals must be investigated until proven harmless — a single occurrence is reason enough, not just recurrence.

Is a resting heart rate of 45 dangerous?

For trained endurance athletes, a resting heart rate between 40 and 60 beats per minute is normal and reflects a larger stroke volume and high parasympathetic tone — not a medical problem. It only becomes concerning in combination: a sudden rise of 5–10 beats above your own normal for several days, dizziness, or declining performance warrant a check-up.

Can too much endurance training harm the heart?

For the vast majority of athletes the benefits clearly outweigh the risks: endurance sport substantially reduces overall cardiovascular risk. There are higher rates of atrial fibrillation, and hints of coronary calcium at extreme distances — but absolute risks remain small. Those who train sensibly, recover from infections fully and use preventive screening benefit for decades.