It’s marathon season.

If you’ve noticed a spike in your friends, family, and colleagues completing long-distance running events, you’re not alone. The cooler months see some of Australia’s biggest running festivals held in Sydney, the Gold Coast, and Melbourne.

From today until the end of the year, there are hundreds of running events scheduled across the country, including the Sydney and Melbourne marathons, which each attract tens of thousands of participants.

But what are the risks during endurance events, and what steps can you take to protect your health?

Long-distance running – defined as any run over 3km – can put stress on the cardiovascular system.

Following a 2025 U.S. study, cardiologist Aaron Baggish concluded that around one in 100,000 marathon runners will have a cardiac arrest.

It’s important to note the extreme rarity of these events, whilst also acknowledging emerging public health concerns. Importantly, there are safety steps runners can follow (more on that later).

Professor André La Gerche, head researcher at the Victor Chang Cardiac Research Institute, noted that exercise in general is “a recognised trigger for cardiac events if you have an underlying condition.”

This can be due to a multitude of reasons, including that the heart has to “work harder,” and that exercise can initiate hormones like adrenaline that “push the system more”.

Interestingly, researchers have noted that runners who have suffered cardiac arrests are not at a lower level of fitness to other athletes.

A 2025 Japanese study measured runners’ pacing across hundreds of marathons over 10 years. It found the fitness levels of those who suffered cardiac arrests were no different to the average participant.

Sudden cardiac arrest occurs when the heart suddenly stops pumping blood. It is considered an electrical problem in the heart. While sometimes described as a heart attack, this is a completely separate condition. La Gerche said it’s “very important in differentiating” sudden cardiac arrest from a heart attack.

He explained cardiac arrest as “when the heart goes into a fast chaotic heart rhythm so that the heart doesn't pump much or even any blood.”

“The end product is that you have someone who's been well and is suddenly dying unless we do something about it,” he said.

The rate of death for sudden cardiac arrest outside of a hospital is 90%.

La Gerche noted “the other part of that is we have to work out why it happened so that we can prevent it from happening again.”

Exercise can also trigger heart rhythm problems “if you’re predisposed to them,” he said.

In 2014, Sydney-based runner Wayne Raven was training for his fifth marathon, describing himself as a “very fit and healthy person”.

He had previously completed the New York and Chicago marathons on multiple occasions, and was gearing up to tackle Chicago for a third time.

On the last kilometre of a 35km training run, Raven had a cardiac arrest.

“I was 34.5kms into the run, feeling a million dollars, looking forward to my coffee that I was going to have after the run,” he told TDA.

“Two days later, I woke up in St. Vincent’s Hospital in an induced coma.”

Raven has no recollection of what happened, but was told a passerby – who he affectionately named ‘Saint Steph’ – found him and performed CPR on him until an ambulance arrived.

“The reality is, if Steph didn’t turn up, I probably wouldn’t be here… She’s my hero,” Raven said.

Doctors realised that Raven’s left ventricle artery had a spasm, blocking the blood from flowing through.

Waking up from his coma, Raven’s first question to doctors was “can I still run the Chicago Marathon?”.

Raven was extremely lucky not to have any brain damage, but did have a stent inserted to ensure his left ventricle stays open.

While his running days are over, Raven’s health and fitness remains very important to him, switching to the exercise bike to “try and keep my heart in good nick”.

La Gerche has researched the exercise paradox. This is where the risk of exercise being a trigger decreases in people who do regular exercise.

“You basically have to regularly train to make exercise safe,” he said.

Looking at short-term safety, La Gerche noted “red flag symptoms” runners should look out for, such as shortness of breath, chest pain, and electrical symptoms like heart palpitations, or feeling lightheaded or dizzy.

Another interesting area of cardiac research is pacing, with La Gerche encouraging runners to stay consistent rather than speeding up at the end.

“Don’t be a hero. Run a good pace, but don’t try to sprint.”

Raven also had advice for runners, telling them to have regular blood tests, be consistent with medication, and his biggest recommendation: “Have a heart health check on a regular basis.”

“It’s the best 10 to 15 minutes investment in your future that you could make,” he said.

Another key point Raven made was about training, saying “there are no shortcuts”.

Raven noted that “all of those things didn’t prevent me from having a cardiac arrest, but what they did do is give me a greater chance of survival.”

Overall, La Gerche said “don’t be fearful” to run “because the net benefits are there,” but “don’t ignore signs and symptoms”.

“Remember that in general, people who run and exercise are healthier than people who don’t,” he said.

For advice around cardiovascular health and testing, always speak to your healthcare professional.

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