"I Want to Push a Little More" ... Can Spell Trouble: The 'Warning Signs' Runners Often Miss [Experiment Notes]

Safety concerns mount after deaths at marathon events
More exercise doesn't necessarily mean greater health benefits
Run at a pace that suits your fitness level, not to beat others' times

In October, when cool weather brings a concentration of marathon events, a series of incidents in which participants have died has heightened interest in running safely. Running is something many people take up for their health, but is it really best to run for as long and as fast as possible?

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At the 2026 Seoul Race Marathon held on October 11, a woman in her 20s collapsed while running and was taken to a hospital, but ultimately died. At the Black Yak mountain marathon event held on September 19 in Chuncheon, Gangwon Province, a man in his 40s also collapsed on a mountain trail and later died.

Running is a quintessential aerobic exercise that helps strengthen cardiorespiratory function and maintain good health. However, more exercise is not necessarily better for your health. So how can you run safely while protecting your heart? We looked at several studies.

Analysis of 29.31 Million Marathon Participants... 176 Cardiac Arrests

Last year, a study analyzing cardiac arrests during marathon events was published in the Journal of the American Medical Association (JAMA). U.S. researchers analyzed approximately 29.31 million finish records from marathons and half-marathons held in the United States between 2010 and 2023.

The analysis found a total of 176 cardiac arrests during the events: 127 men, 19 women, and 30 people whose sex was unknown. Of those, 59 people died. In other words, there was one cardiac arrest for approximately every 167,000 participant records.

The incidence of cardiac arrest was higher among men than women, and higher in full marathons than in half-marathons. Among the 67 cases for which the cause could be identified, the most common was coronary artery disease, a condition involving problems with the blood vessels that supply the heart.

Compared with the period from 2000 to 2009, the proportion of cardiac arrest patients who died fell from 71% to 34%. Prompt cardiopulmonary resuscitation and the use of automated external defibrillators (AEDs), among other emergency responses, may have contributed to the improved survival rate.

Does Running for Longer Make Your Heart Stronger?

Running is a quintessential aerobic exercise. It can help the heart adapt to work more efficiently, for example by increasing the amount of blood pumped with each heartbeat and lowering the resting heart rate.

But does running for longer make the heart stronger? A review published in 2025 in the International Journal of Molecular Sciences examined the effects of long-term endurance exercise on the structure and function of the heart.

According to the researchers, regular aerobic exercise can change the size of the heart muscle and its chambers. Commonly known as “athlete’s heart,” this is a normal process in which the heart adapts to exercise.

However, some athletes who engage in high-intensity exercise over the long term have also shown changes that could pose problems for heart health, including arrhythmias and fibrosis of the heart tissue. The researchers emphasized that “sustained high-intensity training over the long term may increase the risk of cardiac arrhythmias and, in rare cases, may lead to cardiomyopathy,” adding that “athletes with a family history of cardiovascular disease or a history of heart disease should be especially cautious.”

However, the paper analyzed studies on endurance athletes published over a 10-year period and addressed the potential risk of heart disease associated with long-term high-intensity training.

Additional Health Benefits of More Exercise Remain Unclear

Some research suggests that you do not need to run long distances to stay healthy. A study published in the British Journal of Sports Medicine (BJSM) in 2020 combined and analyzed 14 existing studies involving a total of 232,149 people. It found that people who ran had a 27% lower risk of death from any cause than those who did not. Their risk of death from cardiovascular disease was 30% lower, while their risk of death from cancer was 23% lower.

However, increasing the duration, frequency, or speed of running did not lead to a proportional reduction in the risk of death. The researchers explained that running even once a week may be better for your health than not running at all, but that more exercise does not necessarily bring greater benefits.

Your Own Pace Matters More Than Your Time

You should also be careful about suddenly increasing your exercise volume. A study published in the British Journal of Sports Medicine in 2025 followed 5,205 runners for up to 18 months and found that injury rates were higher when runners suddenly increased the distance of a single run.

The researchers examined 588,071 running records. When runners increased the distance of a single run by 10% to 30% compared with their longest run in the previous 30 days, the rate of overuse injuries was about 1.64 times higher. When the distance exceeded twice their previous longest run, the rate was about 2.28 times higher.

“Check Whether You Can Talk While Running”

One simple way to gauge exercise intensity is to check whether you can talk while running. According to the U.S. Centers for Disease Control and Prevention (CDC), moderate-intensity exercise is vigorous enough to make you breathe harder, but still allows you to carry on a conversation. By contrast, if you are so out of breath that it is difficult to say more than a few words, you may be exercising at high intensity.

Even at the same pace, exercise intensity varies from person to person. It is therefore important to run at a pace that suits your fitness level, rather than trying to match someone else’s speed or time.

If you experience chest pain or pressure, dizziness that makes you feel as though you might faint, or unusually severe shortness of breath during exercise, stop running immediately. If you have a heart condition, have fainted during exercise, or have a family history of sudden death at a young age, it is a good idea to consult a medical professional before taking part in a long-distance race.

On social media (SNS), it is easy to find ordinary runners sharing records such as running 1 kilometer in the 3-minute range or completing a sub-three-hour marathon, known as a sub-3, over the full marathon distance of 42.195 kilometers. It is natural to envy someone else’s speed, but not everyone needs to run at the same pace.

It is understandable to want to run faster and farther out of curiosity about “how far I can push myself.” But rather than becoming fixated on your time, choosing a “Fun Run” and enjoying the run itself is also a good option. If you can safely finish today’s run at a pace that suits you and run again tomorrow, that alone can be a meaningful step.

This content was produced with the assistance of AI translation services.