Cardiac changes associated with marathon running vary by age, gender, and training level, findings published in an open-access journal synthesising available data BMJ Open Sports & Exercise Medicine.
However, the findings indicate that it is unclear whether these changes represent a normal physiological response to endurance exercise or are long-term (maladaptive) adaptations.
Researchers note that both low and very high levels of exercise are known to increase the risk of death. Endurance exercise also causes rapid changes in heart function, leading to increases in enzymes, proteins and other substances that indicate tissue damage and inflammation, the researchers added.
However, the researchers note that it is not clear whether these changes are a normal, temporary physiological response to the additional demands placed on the heart under these conditions, or are early signs of potentially harmful long-term adaptations.
To shed more light on this issue, the researchers scoured a research database of relevant studies published in English through April 2025 and compared the effects of marathon running on the heart before and after the event in each study.
The researchers specifically focused on three biomarkers that indicate heart wall stress or damage to the middle layer of the heart wall, the myocardium. Ultrasound scan results (echocardiography) of the heart structures, valves, and pump chambers. and cardiac MRI findings.
The three biomarkers are: Cardiac Troponin T (cTnT). Cardiac troponin I (cTnI); N-terminal proB-type natriuretic peptide (NT-proBNP).
Sixty-nine studies involving 3274 predominantly male (73%) participants aged 27 to 63 years were included in the systematic review, and 49 were included in the pooled data analysis.
The analysis showed that all three biomarkers were consistently elevated within the first hour after completing a marathon, exceeding commonly used clinical thresholds for myocardial damage, blood supply restriction (ischemia), or heart failure.
After running a marathon, there were also various changes to the heart’s chamber volume and pumping mechanics, including the left ventricular ejection fraction, which is a measure of the amount of blood pumped out of the heart’s main pumping chamber (left ventricle) with each beat.
However, these changes were minor and outside the range of what would generally be interpreted as clinically meaningful, the researchers said.
There were no obvious changes in other functions measured by MRI, suggesting that marathon running does not induce visible signs of clinically relevant structural myocardial damage, the researchers said.
Biomarker changes and echocardiographic findings vary by performance run time, age, gender, and training level.
The researchers acknowledge that their findings have various limitations. Of note, most of the study participants were men, and women may have different short- and long-term cardiovascular responses to marathon running, the researchers said. Furthermore, training context, a potentially influencing factor, was also not consistently reported across included studies.
They added that many of the studies included in the review had high scores for risk of bias, indicating there is room for methodological improvement.
“Our combined findings confirm and quantify previously reported increases in cardiac biomarkers and changes in ventricular function after a marathon. However, the clinical relevance of these changes remains unclear,” the researchers note.
“The potential for pathological consequences remains in susceptible individuals and in repeated participation in extreme endurance events,” the researchers added.
The researchers concluded that well-designed long-term studies in diverse groups, including gender and ethnicity, are needed to determine “whether these effects represent a physiological response to extreme levels of exercise or reflect early markers of pathological cardiac remodeling.”
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Reference magazines:
Rayleigh, I others. (2026) Acute effects of marathon running on the heart: a systematic review and meta-analysis. BMJ Open Sports & Exercise Medicine. DOI: 10.1136/bmjsem-2026-003201. https://bmjopensem.bmj.com/content/12/2/e003201.
