More kids are running marathons. A teen's death reignites a debate about the risks

A 15-year-old miss collapsed and died  nigh the finish line of the Leiden Marathon in the Netherlands on Sunday, sparking a conversation about the potential risks of long-distance running as the sport becomes more popular with teens and kids.

The Dutch teen had been competing in the half marathon — a 21.1-kilometre run — when she collapsed about two hours after the start, according to race organizers. Paramedics were unable to resuscitate her.

Police told local media it was a "health issue," and haven't given a cause of death, according to RTL, a Dutch news site.

But the tragedy has nonetheless reignited a debate over age limits in long-distance running. The marathon's rules said participants in the half marathon needed to be at least 16 years old.

Athletics Canada has similar recommendations, and says in its guidelines for kids and youth in road races that "systematic training and participation in long distance endurance events pose certain risks for individuals who have not yet reached full maturity."

While there's variation on the specific age guidelines for running longer distances, the sport governing body says the general consensus is people should be at least 18 to compete in a full 42-kilometre marathon, and children shouldn't run 10-kilometre races until after puberty.

As for half marathons, Athletics Canada suggests participants should be at least 16.

Exercising too hard is landing some young women in hospital, experts warn

While endurance exercise is generally well tolerated by healthy people, it can carry some risks, both in terms of immediate health considerations and long-term athlete development, said Chris Winter, Athletics Canada's director of domestic programs and safe sport.

But at the same time, Winter and other health experts emphasize the benefit of regular exercise, like running, in kids.

"As a healthy living advocate, I get scared by these catastrophic events where we focus only on risk and not the hundreds of thousands of people whose lives have been improved and their longevity extended because they ran," said Dr. Mark Tremblay, a senior scientist with the Healthy Active Living and Obesity research group at CHEO children's hospital in Ottawa.

Anyone who has tried to register for a marathon in the last few years can tell you how popular they've become.

A record 1.3 million people have already applied to run the 2027 London Marathon. So many people have tried to register for the Boston Marathon in recent years that they've tightened their qualifying times.

And it's not just adults signing up for the gruelling races.

"With the increased interest in endurance and ultra distance running, we have certainly seen more youth participating in long-distance events," Winter said.

Hundreds of middle school and high school students ran the L.A. Marathon in March. In 2022, a six-year-old runner made headlines for completing the Flying Pig Marathon in Ohio.

Last year, a 10-year-old ran the Blue Nose Marathon in Halifax. And in September, a B.C. Teen became the youngest person ever to complete a 320-kilometre ultra marathon called The Divide 200, finishing in 78 hours.

Some other headlines are scarier, like a 21-year-old Texas student athlete who died on the track in April (his cause of death hasn't been reported, other than a "medical emergency,") and a 14-year-old Florida boy who died running a 5K in 2023 after suffering cardiac arrest.

Sudden cardiac death in young, apparently healthy athletes is rare, but attracts significant attention in the medical community and the media, according to a 2024 literature review in the Journal of the American College of Cardiology.

The most common reasons for these deaths are underlying, inherited cardiac conditions and congenital abnormalities, the review's authors wrote.

There tend to be more strict age guidelines on the official marathon circuit, like the World Marathon Majors. Boston and London, part of the majors, don't allow participants younger than 18 on race day, for instance.

And at the Toronto Waterfront Marathon, runners in the full 42-kilometre race must be 18 on race day, 16 if they're running the half marathon, 10 years old for the 10K and eight for the 5K.

But how do organizers enforce it? Leiden Marathon race director Tjeerd Scheffer told local media, "Our system is based on the age details that the participants provide." 

Some races require a valid photo ID during bib pickup to verify name and age. Other organizations, such as Vancouver's RunVan, require parents or guardians to sign waivers for any participants under age 18. RunVan also notes it reserves the right to ask for proof of age.

These are precautionary guidelines enforced with different levels of vigour in different jurisdictions at different times. They're also imperfect, because the risks depend on the individual person, their own physiology and health conditions and their maturity, Tremblay explained.

"This person could have been 15.99, and if they waited one more day and run a half marathon, would it have made a difference? Almost certainly not," he said, using the Dutch teen as an example.

Kids have immature bones, and ligaments and muscles that are growing at different rates, explained Tremblay, who is also professor of pediatrics at the University of Ottawa. When you put heavy stress on them, they're more susceptible to orthopedic problems.

A child's thermoregulatory system is still developing, he added, so they don't do as well in the kinds of extreme weather conditions — like heat — you might find on a race course. Athletics Canada notes that children produce less sweat, so have a harder time cooling down compared to adults.

Mentally, they might not have learned how to pace themselves properly yet, either.

But risk also depends on the person, and Tremblay stressed that for the vast majority of teens, running a half marathon would be absolutely fine and, in fact, a better alternative to the health risks of being inactive.

And at the same time, he said, even running a short distance could be unadvisable for some adults, depending on their health and underlying conditions.

"I wouldn't encourage that more is better, but I would encourage the habitual nature of it," he said.

Winter, with Athletics Canada, said that's why they focus on youths' participation and individual improvement in road races instead of performance. They don't offer provincial or national road running championships for younger age groups, nor do they keep records or ranking or present annual awards.

"To be clear, serious health emergencies, such as the incident that took place in the Netherlands, while tragic, remain very rare, and the overall benefits of regular exercise far outweigh the potential risks," he said.

Senior Writer & Editor

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