This year the Moscow Marathon drew more than 45 thousand participants, and Berlin a comparable crowd. Most finishers have raised troponin in their blood that same day — the very protein emergency departments use to diagnose a heart attack. A new meta-analysis has, for the first time, pulled these data into a single picture, showing how large the shift is and what else happens to the heart after 42 kilometres.

What the researchers did

Researchers from the cardiology department of Amsterdam University Medical Center (the Netherlands), together with colleagues from the University of Indonesia (BMJ Open Sport & Exercise Medicine, June 2026), screened 9080 publications from 1978 to 2025.

The review included 69 studies with 3274 participants — healthy adults who had run a road marathon.
73% were men, aged 27 to 63, ranging from beginners to well-trained runners.
49 studies made it into the meta-analysis: three blood markers, 18 cardiac ultrasound measures and five MRI measures.
Blood and ultrasound were compared “before the start” (no earlier than two weeks prior) and “after the finish” (within a day); MRI within three days.

What they found

Blood markers rose in every study:

troponin T — by an average of 42 ng/L;
troponin I — by 75–77 ng/L (the figures differ slightly between the main text and the abstract);
NT-proBNP, a marker of cardiac wall stretch, — by 114 ng/L.

The authors state plainly that these values are above the thresholds used clinically to diagnose myocardial injury, ischaemia and heart failure. The spread is huge: the rise in troponin I ranged from 20 to 200 ng/L across studies.

Cardiac ultrasound:

left ventricular end-diastolic volume fell by 5–9%;
right ventricular volumes, by contrast, rose by 16–28%, while its contractility dipped slightly (ejection fraction −6%, TAPSE −4%);
the E/A ratio, a measure of how the heart relaxes, dropped by 33% — but stayed within the physiological normal range.

MRI found no signs of structural damage. Left ventricular ejection fraction even rose slightly — by 1.9 percentage points.

Who takes the biggest hit

A meta-regression showed what the size of the shift depends on:

NT-proBNP was higher in those who ran longer: plus 20 ng/L for every 10 minutes of finishing time;
higher in older runners — plus 38 ng/L for every 10 years of age;
higher in groups with a larger share of women;
troponin I was higher in less-trained groups.

In other words, the marathon “shakes up” the heart most not in the elite, but in the recreational runner who spends five hours on the course with an inadequate base.

Is it harmful?

The authors' honest answer: we don't know. Most cardiologists regard the post-exercise rise in troponin as benign: heart muscle cells temporarily become “leaky” and release the protein into the blood, and within 24–72 hours levels return to normal. But in some people such a rise may unmask hidden disease — coronary atherosclerosis, for example, especially at an older age. No one has yet shown a direct link between post-finish troponin and future cardiac events.

A related but separate topic is atrial fibrillation in endurance athletes, whose risk really does rise with years of high-volume training. But that is a long-term effect, not a one-day response.

Limitations

No control group — every study was designed as “before and after” in the same people.
Of the 69 studies, 7 had a high and 17 an unclear risk of bias; only six calculated their sample size in advance.
Methods varied: only a minority of studies used high-sensitivity troponin assays, and the timing of blood draws after the finish differed.
Few women (about a quarter), so conclusions about sex differences are preliminary.
The meta-analysis describes the first days after the finish. It cannot tell us what remains years later.

How to apply this

If you end up seeing a doctor after a marathon, tell them you ran one. Troponin on the first day after the finish can easily “paint” a heart attack, which risks unnecessary tests. The authors explicitly warn about possible misdiagnosis.
But don't blame everything on the marathon. Chest pain or pressure, fainting, palpitations or skipped beats, breathlessness at rest after the finish — call an ambulance rather than waiting for it to “pass on its own”. Raised troponin in a runner does not rule out a real heart attack.
Prepare properly rather than just “getting through it”. The larger shift in slower and less-trained runners is an argument for a solid base before your first marathon. You can check whether your goal is realistic in the race planner.
If you are over 40 or have risk factors — get an ECG and see a cardiologist before your first marathon, not after.
Don't schedule blood tests for the first few days after a race — troponin, NT-proBNP and a number of other values will be skewed.

The bottom line

69 studies and 3274 marathon runners: troponins and NT-proBNP rise after the finish in every study and on average cross the clinical thresholds for heart attack and heart failure.
The right ventricle temporarily dilates and the heart's relaxation changes, but MRI finds no signs of damage.
NT-proBNP rises more in older and slower runners, troponin I in less-trained ones.
Whether this is dangerous in the long run has not been established. The practical takeaway: tell your doctor about the marathon, but never ignore chest pain.

Sources: Laily I., van Steijn N., Rizki P., de Vries R., Liastuti L.D., Zwinderman A.H., Verhagen E., Bakermans A.J., Jorstad H.T. “Acute effects of marathon running on the heart: a systematic review and meta-analysis”. BMJ Open Sport & Exercise Medicine, 2026;12(2):e003201. DOI: 10.1136/bmjsem-2026-003201