Marathons Stress the Heart—but Do They Cause Lasting Harm?

Marathon running has grown in popularity as a test of endurance and fitness. Yet, the effects of such extreme exercise on the heart remain unclear. Researchers continue to explore whether the sport causes lasting damage or only temporary changes. A recent meta-analysis found three cardiac biomarkers—cTnT, cTnI, and NT-proBNP—rise sharply within the first hour after a marathon. These levels often exceed clinical thresholds for heart stress. However, cardiac MRI scans showed no consistent signs of structural heart injury after the race.

Echocardiography revealed modest changes in heart chamber size and left ventricular ejection fraction. These shifts mostly stayed within safe clinical limits. Variations in biomarker levels and functional changes depended on factors like finishing time, training level, age, and sex.

Most studies focused on male runners, leaving gaps in understanding how women’s hearts respond. Researchers now call for broader inclusion of women, diverse ethnic groups, and detailed training data in future work. Long-term studies are also needed to track athletes’ heart health over time and assess the impact of repeated extreme exertion. The findings suggest marathon running triggers short-term cardiac stress but no clear structural damage. Experts emphasise the need for more diverse and long-term research. This will help develop better exercise guidelines and personalised risk assessments for athletes.