Exercise blurs the line on cardiac blood tests

Troponin and natriuretic peptides are the workhorse blood tests for suspected heart muscle injury and strain, and their cut-offs were built from general clinical populations. Hard exercise itself pushes these markers up, so an athlete who has a blood test after a race or a heavy training block can look abnormal without being ill. That creates a genuine diagnostic problem: distinguishing myocardial disease from physiological adaptation. This review set out to map what is known about how these markers behave in athletes and active individuals, and how clinicians should interpret them.

The authors conducted a clinical review of exercise-induced elevations in cardiac biomarkers. They examined the pathophysiology, release kinetics and diagnostic performance of established markers — high-sensitivity troponin I and T, BNP and NT-proBNP — alongside emerging candidates including galectin-3, ST2, GDF-15, heart-type fatty acid-binding protein and cardiac myosin-binding protein-C. They also catalogued the weaknesses of the existing evidence base and set out where these tests are actually used in practice: assessing acute cardiac stress, separating athlete's heart from cardiomyopathy, and deciding on return to play after myocarditis.

The headline problem is scale: between 74% and 96% of marathon runners exceed standard high-sensitivity troponin thresholds, meaning the usual cut-off says little about an individual endurance athlete. The review identifies the absence of athlete-specific reference ranges as the central limitation, compounded by small sample sizes in most studies (most under 100 participants), short follow-up and highly varied exercise protocols. Emerging markers were examined but none is established. The authors also push back on speculative applications, stating that artificial-intelligence multi-omics, tailored molecular exercise prescription and real-time monitoring remain theoretical without thorough confirmation.

This consolidates a long-standing observation in sports cardiology rather than overturning it: the same test can mean different things in a trained and an untrained person. It extends the discussion to newer candidate biomarkers while making clear they are not yet ready for clinical use. The open questions the authors name are concrete — sport-specific 99th percentile thresholds, large prospective cohorts with 5-10 year follow-up, standardised methods and validated point-of-care testing. Until those exist, interpretation rests on clinical judgement rather than a defensible numerical boundary.

If you train hard and have blood work done soon afterwards, a raised cardiac marker is not automatically a sign of heart damage, and this review's position is that such rises in people without symptoms are usually transient. That is a reason to consider recent training when reading a result, not a reason to dismiss one. The review draws a line at elevations that persist beyond 72 hours or come with symptoms, which it says warrant further investigation. Any interpretation of your own results is a conversation for a clinician who knows your training history.