South Korean running influencer Yoo Ji-won, 25, died after collapsing just before the finish line of a half-marathon in Seoul on October 11, 2026. The young athlete lost consciousness at the 20.6-kilometre mark of the Seoul Race, leaving her less than 500 metres from completing the 21.1-kilometre event. She received emergency first aid, including cardiopulmonary resuscitation (CPR), and was rushed to a hospital. However, she could not be revived. The race organisers later confirmed her death and expressed condolences.

The statement read, "On October 11, at approximately 8:49 AM, a participant in the Seoul Race half-course collapsed at the 20.6km mark. Following emergency aid at the scene, the individual was transported to a medical facility via a 119 ambulance for treatment; however, we are saddened to report that they have passed away."

"We pray for the soul of the dead and extend our deepest condolences to the bereaved family, who are now facing such a sudden and profound loss. We also offer our heartfelt comfort to all participants who may be feeling deeply saddened by this tragic news."

Yoo was known for sharing her running journey and achievements on social media. Even though running is known to offer several health benefits, prolonged and intense physical activity can add significant stress on the body. In some cases, an underlying medical condition or a sudden health emergency can have serious impacts.

How Can A Runner Collapse During A Half-Marathon?

A half-marathon requires runners to sustain physical activity over a long distance. During the race, the heart pumps more blood to the muscles, breathing becomes faster, and the body produces heat. These are normal responses to exercise, but there can be problems when the body cannot cope with the demands placed on it or when there's an underlying health issue. There are several factors that can cause a participant to suddenly collapse. Here, take a look at some of these causes.

1. Sudden cardiac arrest

Sudden cardiac arrest happens when the heart suddenly stops pumping blood. This can occur due to an electrical problem that affects the heart's rhythm. The brain and other vital organs are deprived of oxygen, and the person may lose consciousness within seconds. Although cardiac arrest is uncommon among runners, it can occur even in young people who appear healthy.

2. Undiagnosed heart conditions

Some heart conditions may remain unnoticed until a person performs some strenuous physical activity. For example, hypertrophic cardiomyopathy causes abnormal thickening of the heart muscle, while certain electrical disorders can cause dangerous heart rhythms. These conditions may not always have obvious symptoms during everyday activities. However, intense exercise can increase the strain on the heart and, in some cases, trigger a serious event. Warning signs such as chest pain, unexplained breathlessness, fainting during exercise or a family history of sudden cardiac death should not be ignored.

3. Dehydration and electrolyte imbalance

Runners lose water and electrolytes, including sodium, through sweat. If fluid loss becomes excessive, dehydration can impact circulation and make it harder for the body to regulate its temperature. An electrolyte imbalance can also interfere with normal muscle and nerve function. In severe cases, it may lead to severe heart rhythm disturbances. Runners should follow an appropriate hydration plan rather than drinking excessive amounts of water.

4. Heat-related illness

Running generates heat, and hot or humid conditions can make it harder for the body to cool itself. If the body's temperature rises excessively, a runner may develop heat exhaustion or heatstroke. Heatstroke can affect the brain and other organs and it can become life-threatening without immediate treatment. Dizziness, nausea, weakness, confusion and unusual behaviour during a race can indicate a heat-related problem.

How Can Runners Reduce Their Risk?

  • Get medical advice: People with known heart conditions, unexplained fainting or other symptoms should consult a doctor before strenuous exercise.
  • Train gradually: Increase running distance and intensity in a progressive manner rather than making sudden jumps.
  • Stay hydrated: Drink according to individual needs and conditions, avoiding both dehydration and excessive fluid intake.
  • Recognise warning signs: Stop immediately if you experience chest pain, unusual breathlessness, dizziness, palpitations or sudden weakness.
  • Emergency preparedness: Race organisers should ensure that trained medical personnel, CPR and automated external defibrillators (AEDs) are readily available.

A person who suddenly collapses and does not respond may be experiencing cardiac arrest. Call emergency services immediately, check for normal breathing and begin CPR if the person is unresponsive and not breathing normally.

Disclaimer: This content including advice provides generic information only. It is in no way a substitute for a qualified medical opinion. Always consult a specialist or your own doctor for more information. NDTV does not claim responsibility for this information.