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If you’re considering an Ironman, marathon or triathlon, read this first

Prof Niall Moyna: Data on triathlons should give competitors pause for thought, especially men in middle age

The tragic deaths of Brendan Wall and Ivan Chittenden during the Youghal Ironman triathlon last weekend shocked many of us and sparked a debate regarding the safety of competing in extreme endurance events generally.

Exercise is probably the most potent medicine available to maintain and improve health. However, like any medication, it should ideally be prescribed in optimal doses to ensure maximal benefits and minimise harm. Extreme levels of exercise, beyond that recommended for health, may in fact may be counterproductive and increase the risk for injury, illness and even death.

Recent data about competing in events such as triathlons should give competitors pause for thought – especially if they’re thinking about training for and participating in an endurance competition for the first time.

These ultra-endurance races combine three sports – a swim, followed by a bike ride and finishing off with a run. The event in Youghal last weekend consisted of a 1.9km swim, a 90km cycle and 21.1km run.


Participants in the Ironman World Championship held annually in Kona, Hawaii – this years the men’s race is being held in Nice – are given 17 hours to finish an event involving a gruelling 3.86km swim, followed by a 180.2km bike ride and ending with a full 42.2km marathon. But first, they must compete in qualifying Ironman competitions and place within the top ranks depending on their age group to qualify among the 2,500 competitors. This qualification criteria appears significant when we look at the data for medical outcomes.

Research by a team led by Dr Douglas Hiller – an orthopaedic surgeon and clinical professor at Washington State University in the US and a specialist in endurance sports, their physiological effects and ramifications – assessed the injury and illness characteristics among the participants in the Ironman World Championship between 1989 and 2019. The research team spent 3,500 hours meticulously combing through more than 10,000 medical records. Their findings were published in May in a paper authored by Paal Knudtzon, a research fellow at Cedars-Sinai Medical Center in Orthopaedic Spine Surgery and Neurosurgery.

They reveal that out of 47,465 participants who competed in the event during the 30-year period, 22 per cent or 222 per 1,000 competitors were evaluated and treated by a member of the medical staff. Common complaints were dehydration, nausea, dizziness, exhaustion, muscle cramps and vomiting. Life-threatening medical conditions that required hospitalisation were relatively rare at approximately 2 per cent and included concussion, palpitations, chest pain, abnormal heart rhythms, hyperthermia, severe electrolyte disturbances and seizures.

No deaths

However, no deaths were reported during the 30 years of the Ironman World Championship. The authors of the research paper attribute the complete absence of fatalities to the rigorous self-selection of athletes qualifying for the event.

By the time they reached 60 years of age, men had an eight times higher risk of death during a triathlon than men under 30. Women were 3.24 times less likely to die or have a cardiac arrest

But another study undertaken by Dr Kevin Harris and his colleagues at the Minneapolis Heart Institute in the US gives more cause for concern. It examined the incidence of death among almost 5 million participants competing in a range of USA Triathlon-sanctioned events with no qualification criteria between 2006 and 2016. There were 1.74 sudden deaths, cardiac arrests, and trauma related death for every 100,000 participants. None of the deaths occurred among elite or professional athletes.

Worryingly for people who come to endurance sport in middle-age, the rate of death and cardiac arrests increased incrementally in men by the decade. By the time they reached 60 years of age, men had an eight times higher risk than men 30 years or younger. Women, on the other hand, were 3.24 times less likely to die or have a cardiac arrest than men during a triathlon. Pre-existing heart conditions were identified in 44 per cent of the participants who died while competing in a triathlon.

Two-thirds of all deaths and cardiac arrests during a triathlon occurred during the initial swim, with the majority being found unconscious. The high fatality rate during the swimming leg of the triathlon may seem surprising considering that the competitors are likely to be relatively fresh and not suffering from the heat or fatigue.

Several reasons have been put forward to explain this observation. Firstly, the high levels of anxiety and pre-race excitement may result in a surge in adrenaline at the beginning of the race that may trigger abnormal heart rhythms in susceptible but unsuspecting competitors. Secondly, participants who are not familiar with open water swimming may have difficulty dealing with adverse environmental conditions such as cold water and large waves, and also with the high rate of collisions that may occur when a large number of swimmers are in close proximity. The delay in recognising and rescuing swimmers in distress and getting them to dry land may also be a contributing factor.

A phenomenon called swimming-induced pulmonary oedema (SIPE) that can occur particularly in cold water swimming may help to shed more light on these findings. Swimming in cold water diverts blood from the extremities to maintain core temperature. This can cause the blood pressure to increase in the small capillaries, resulting in abnormal levels of fluid leaking out of blood vessels and into the air sacs of the lungs. The filling of the air sacs with fluid – known as pulmonary oedema – can dramatically reduce normal oxygen and carbon dioxide movement through the lungs. There is growing body of evidence linking SIPE to fatalities in susceptible individuals during swimming, especially in cold water.

That’s not to say that the only high-risk endurance sports involve triathlons or swimming. Marathons and the associated high volume of training can also expose runners to a range of risks including recurrent stress and injury to the heart muscle, calcification of the coronary arteries, development of abnormal heart rhythms, and scarring in the heart.

If you are considering doing a triathlon or a marathon, you need to be aware of the risks involved, have a training plan and prepare diligently

Dr Hiller believes that every effort should be made to prevent fatalities during triathlon events. Given the risks, a Global Triathlon Safety Task Force has been formed to address the health and safety issues associated with participation in triathlons. The sport’s international governing body is collecting and analysing data. Dr Hiller believes this will allow “us to make recommendations to athletes, race organisations and care providers that will improve safety and reduce fatalities”.

Extremely rare

Despite all this, it is important to remember that sudden death during exercise is extremely rare. If you are considering doing a triathlon or a marathon, you need to be aware of the risks involved, have a training plan and prepare diligently. You should seek appropriate medical clearance if you have any health concerns. Non-invasive tests such ultrasound imaging, cardiac magnetic resonance imaging (MRI) and computerised tomography (CT) coronary angiography are now routinely used to check for range of heart conditions.

The events in Youghal last weekend should not deter anyone from undertaking regular exercise. Despite the headlines about the tragedy, the benefits of exercise far outweigh the risks for most adults. But as with most things, moderation is the key.

Niall Moyna is a full professor of clinical exercise in the school of health and human performance at Dublin City University.