IPM Take
Exercise remains one of the strongest interventions available for cardiovascular prevention, but the hearts of people who have exercised intensively for decades do not always look like the hearts on which conventional diagnostic thresholds were built.
That is the tension running through a new American College of Cardiology review of sports-cardiology evidence from 2026.
Masters athletes, generally adults aged 35 and older who continue competitive or high-volume recreational exercise, can develop substantial physiological cardiac remodelling. Their chambers may enlarge, resting heart rates may slow and imaging can show findings that would attract concern in a sedentary patient. At the same time, endurance athletes appear to have more atrial fibrillation and, among men, more coronary artery calcification than less-active peers.
None of this overturns the cardiovascular benefits of exercise.
It does something more clinically awkward: it makes “normal” harder to define.
A highly trained 55-year-old with an enlarged left atrium, sinus bradycardia and a high coronary calcium score cannot simply be interpreted using the same assumptions as a sedentary 55-year-old. Conversely, physicians cannot dismiss every abnormality as an athlete’s heart because ventricular arrhythmias, disproportionate right-ventricular dysfunction or certain patterns of myocardial scar can signal genuine disease.
That creates a precision-cardiology problem hiding inside sports medicine.
The policy risk lies at both extremes. Overdiagnosis can lead to unnecessary testing, anxiety and exercise restriction in people who may derive enormous health benefit from remaining active, while under-recognition can label genuine pathology as harmless adaptation.
Sports cardiology increasingly needs something conventional medicine often struggles to deliver: diagnosis in context.
Executive Summary
An American College of Cardiology expert analysis published on 16 October 2026 synthesised several major developments in sports cardiology, including the joint ESC/ACC clinical consensus statement on masters athletes with abnormal cardiovascular findings, a state-of-the-art imaging review and new studies examining training load and long-term disease risk.
Masters athletes are generally defined as adults aged 35 years and older who engage in competitive or high-volume recreational sport. They derive substantial health benefits from long-term physical activity, but emerging evidence suggests that particular cardiovascular findings occur more frequently in this population.
Atrial fibrillation is one of the clearest examples. Masters athletes have higher prevalence and incidence of atrial fibrillation despite often having fewer traditional cardiovascular risk factors, although absolute rates are lower among female athletes.
At the same time, several findings that might appear pathological in another patient can represent normal exercise adaptation. Sinus bradycardia, first-degree atrioventricular block and Mobitz type I block can occur commonly in endurance athletes, while proportional chamber enlargement and small areas of fibrosis at right-ventricular insertion points may also be benign.
Other findings require more caution. Ventricular arrhythmias are not considered a normal adaptation, and disproportionate right-ventricular dilation, dysfunction or extensive fibrosis can raise concern about underlying cardiomyopathy.
Coronary imaging adds another paradox. Male endurance masters athletes may have more coronary artery calcification and atherosclerosis than sedentary peers, yet high cardiorespiratory fitness appears to attenuate, without eliminating, the cardiovascular risk associated with elevated calcium scores.
Separate research involving 151 male endurance athletes found that total training duration was a stronger determinant of cardiac remodelling than training intensity or session frequency, suggesting that cumulative exercise exposure is particularly important in shaping the athlete’s heart.
A large UK Biobank analysis meanwhile found that a greater proportion of total physical activity performed vigorously was associated with lower rates of cardiovascular and several non-cardiovascular diseases independently of total activity volume. Because that study was observational, it cannot establish that vigorous exercise itself caused the reduction in disease risk.
Taken together, the evidence argues against interpreting athletic hearts using isolated measurements. Training history, symptoms, exercise capacity, rhythm, imaging pattern and the proportionality of remodelling increasingly need to be considered together.
Why it matters
- HTA bodies: Advanced echocardiography, cardiac MRI, coronary CT and wearable rhythm monitoring are increasingly entering sports-cardiology pathways. Their value depends heavily on interpretation because detecting more abnormalities does not necessarily improve outcomes. Assessment should therefore consider whether additional imaging meaningfully distinguishes dangerous pathology from physiological remodelling rather than simply increasing diagnostic yield.
- Payers: Highly active adults may undergo repeated imaging, rhythm monitoring and stress testing when standard thresholds generate uncertain findings. Better sports-specific diagnostic pathways could reduce unnecessary downstream investigations while ensuring that athletes with genuine coronary disease, cardiomyopathy or clinically important arrhythmia receive appropriate care.
- Industry / innovation partners: Wearables and advanced imaging technologies are generating unprecedented amounts of cardiovascular information from athletic populations. The opportunity increasingly lies not in detecting every deviation from population norms, but in developing tools capable of interpreting those findings against training exposure, age, sex and longitudinal change.
Exercise is supposed to make the heart healthier, which makes it unsettling when the heart of someone who has trained for decades begins to look abnormal.
That apparent contradiction is becoming one of the central challenges in sports cardiology as more people continue endurance sport and high-volume training into middle and older age. The clinical problem is not that exercise has suddenly become dangerous, because decades of evidence continue to show substantial cardiovascular and overall health benefits from physical activity. The difficulty is that sustained training changes the cardiovascular system, sometimes profoundly enough that the boundary between adaptation and disease becomes blurred.
The American College of Cardiology’s latest review of 2026 sports-cardiology research captures that tension. Masters athletes, defined broadly as people aged at least 35 who regularly participate in competitive or high-intensity recreational exercise, often arrive in clinics with cardiovascular findings that were originally defined in much less active populations. Applying conventional thresholds without considering training history can therefore create a diagnostic trap.
A slow resting heart rate is an obvious example. Sinus bradycardia is common in endurance athletes, as are first-degree atrioventricular block and Mobitz type I conduction patterns. In a sedentary patient, these findings may prompt concern about conduction disease, yet in a highly trained athlete they can reflect long-standing autonomic and electrical adaptation.
Cardiac imaging creates the same problem at a more sophisticated level. Years of endurance training can enlarge both ventricles and the atria while increasing myocardial mass, producing a heart that looks structurally different from that of someone who exercises little. Left atrial enlargement, for example, is not automatically pathological when it appears proportionally alongside broader athletic remodelling, while small focal areas of fibrosis at right-ventricular insertion points on cardiac MRI can occur without evidence of cardiomyopathy.
The clinical danger begins when adaptation is used too casually as an explanation.
Ventricular arrhythmias are not regarded as a normal consequence of training, while disproportionate right-ventricular enlargement, impaired right-ventricular function, dyskinesis or extensive myocardial fibrosis can signal genuine pathology. The joint ESC and ACC consensus therefore places heavy emphasis on pattern recognition rather than any single measurement, asking whether the overall cardiovascular phenotype makes sense in relation to the athlete’s training exposure, symptoms, family history and performance.
That last point has become more important because researchers are beginning to quantify training exposure much more precisely.
A 2026 European Heart Journal study used chest-worn heart-rate monitors and cardiac MRI in 151 male endurance athletes, including younger athletes aged 16 to 23 and middle-aged men aged 45 to 70. Rather than relying on estimates of exercise from questionnaires, participants had to record at least 80% of their training sessions over approximately three months.
The results showed a remarkably consistent relationship between the amount of training and the structure of the heart. As cumulative exercise exposure increased, left- and right-ventricular volumes and left-ventricular mass increased progressively as well.
The most interesting finding was what drove those changes.
Total training duration proved to be a stronger predictor of cardiac remodelling than exercise intensity or the number of training sessions, while time accumulated in lower heart-rate zones showed particularly strong associations with chamber enlargement. Higher-intensity exercise contributed less to structural remodelling than the investigators initially expected.
That finding changes the way an enlarged athletic heart can be interpreted because it suggests that years of high-volume training may matter more structurally than repeated bursts of extreme intensity. An athlete who has spent thousands of hours cycling, running or swimming may therefore develop extensive remodelling even if much of that training occurred at relatively moderate intensity.
The difficulty is that structural adaptation and cardiovascular risk do not necessarily move in the same direction.
A separate UK Biobank analysis examined the proportion of total activity performed vigorously among adults aged 40 to 69 and found that people who performed a greater share of their physical activity at vigorous intensity had lower observed rates of multiple chronic diseases and all-cause death, even after accounting for total activity volume.
For major cardiovascular events, estimated five-year risk declined from 10.16% among participants reporting no vigorous physical activity to 6.41% among those for whom more than 4% of activity was vigorous.
That finding is observational, which means it cannot prove that increasing vigorous activity itself produced the lower risk. Healthier people may simply be more capable of exercising vigorously, while lifestyle, socioeconomic and other factors can influence both activity patterns and outcomes.
Even so, the contrast is important. Training volume appears to drive much of the structural remodelling seen in endurance athletes, while a greater proportion of vigorous activity is associated with better long-term health outcomes. The heart can therefore look progressively more unusual without the athlete necessarily becoming progressively less healthy.
Coronary artery calcium creates an even sharper version of that paradox.
Male endurance masters athletes have been reported to show more coronary artery calcification and atherosclerosis than sedentary counterparts, an observation that initially appears difficult to reconcile with the cardiovascular benefits of exercise. Yet higher cardiorespiratory fitness appears to reduce, although not eliminate, the risk associated with elevated coronary calcium.
That means an asymptomatic athlete with a high calcium score should not automatically be told to stop exercising, nor should the finding simply be ignored because the patient is fit.
The current consensus specifically cautions against reflexive restriction in asymptomatic athletes with elevated coronary calcium and notes that evidence does not support empirically giving aspirin simply because a high score has been detected before competition. Instead, risk factors and symptoms need to be considered alongside the imaging result.
This is where conventional diagnostic medicine can struggle.
Most disease thresholds are built by comparing patients against population norms. Sports cardiology increasingly has to ask whether the reference population itself is appropriate.
An enlarged right ventricle means something different when found in someone who has spent 20 years competing in endurance sport than when identified in a sedentary patient with unexplained breathlessness. A resting heart rate of 42 beats per minute can be entirely physiological in one patient and evidence of conduction disease in another. Myocardial fibrosis can be incidental in one pattern and deeply concerning in another.
Context is therefore becoming part of the diagnostic test.
That also changes how stress testing should be performed. Standard protocols designed for typical clinical populations may not push highly trained athletes hard enough to reproduce symptoms or expose exercise-related abnormalities. Sports-cardiology guidance increasingly favours testing that reflects the athlete’s actual sport and continues to true peak effort rather than stopping at workloads that would be demanding for an average patient but routine for the athlete.
Wearables are adding another layer of complexity because athletes now arrive with months or years of rhythm, heart-rate and training-load information collected outside the clinic. That data can reveal patterns traditional testing would miss, but it can also identify benign irregularities that trigger anxiety and additional investigation.
The challenge is no longer finding cardiovascular abnormalities.
Technology is becoming exceptionally good at that.
The challenge is deciding which abnormalities matter.
That distinction has direct consequences for exercise participation because unnecessary restriction carries its own cost. Masters athletes often have decades of identity, social connection and physical health invested in sport. Advising them to stop training based on an uncertain imaging finding is not a neutral decision, particularly when continued physical activity itself offers substantial protection against cardiovascular and non-cardiovascular disease.
At the same time, reassurance cannot become the default simply because a patient is fit. Coronary artery disease remains the leading cause of sudden cardiac arrest among masters athletes, while ventricular arrhythmias and certain patterns of myocardial scar can signal pathology that deserves investigation.
The emerging approach is therefore neither “exercise is always protective” nor “extreme exercise damages the heart”.
It is more demanding than either slogan.
Cardiology has to understand what decades of exercise normally do to the heart well enough to recognise when a finding no longer fits that physiological story.
That makes sports cardiology an increasingly important test case for precision medicine because the same measurement can mean different things depending on the person in whom it appears.
The athlete’s heart may be larger, slower and structurally different without being diseased, while a highly fit person can still develop atrial fibrillation, coronary disease or cardiomyopathy.
As lifelong exercise becomes more common, the clinical challenge will not be persuading cardiologists that exercise is good for the heart. It will be teaching the health system how to recognise when a heart shaped by exercise is healthy, and when the apparent adaptation is something more.
