Triathlon

Is triathlon safe?

Mostly, but it carries more risk per race than a marathon. The danger sits in the first few hundred metres of the swim. Most of the people who die are middle-aged and older men with heart disease, and the trigger is a crowded, cold, adrenaline-filled mass start.

The best US figures come from Kevin Harris and colleagues at the Minneapolis Heart Institute. Their 2017 study in the Annals of Internal Medicine found 1.74 deaths or cardiac arrests per 100,000 participants in USA Triathlon races from 2006 to 2016, among 4.8 million starters. That includes people who were resuscitated. An earlier study by the same group found 1.5 sudden deaths per 100,000 for 2006–2008. In the UK, British Triathlon events had 5 deaths in 991,186 starts from 2009 to 2015, or 0.5 per 100,000.

Putting those together, we estimate about 10 micromortsMicromortA one-in-a-million chance of death. It lets you compare the risk of very different activities on one scale.More in the glossary per race (our estimate). That is around three times a marathon and two or three skydives.

Why the swim?

Of the 120 sudden deaths and cardiac arrests the US study found from 1985 to 2016, 90 happened in the swim, 15 on the run, 7 on the bike and 8 after the finish. A further 15 deaths were from trauma on the bike leg, mostly crashes.

The swim combines several stresses at once. Cold water can trigger a gasp reflex and a jump in heart rate and blood pressure. Hundreds of swimmers start together, with kicks, elbows and swallowed water. A wetsuit can feel tight across the chest, and nervous athletes often sprint the first minutes far above their training pace. For a heart with narrowed arteries or a thickened muscle, that is a dangerous moment.

The rescue problem makes it worse. A runner who collapses falls on a road in front of marshals. A swimmer who loses consciousness slips under the surface, in murky water, among hundreds of splashing arms. By the time anyone notices, minutes may have passed.

Who is at risk

Age and sex dominate. Men had more than three times the rate of women, 2.40 against 0.74 per 100,000. For men aged 60 and over, it was 18.6 per 100,000, about ten times the overall average. The average age of the victims was 47, and 85% were men.

Autopsies point to hidden heart disease. Of 61 people who died and had an autopsy, 27 (44%) had relevant cardiovascular abnormalities, mostly coronary artery disease or cardiomyopathy. A UK study of coroners' records found heart disease was a cause or contributing factor in half of triathlon deaths.

Race distance matters less than people think. US rates were similar for short, intermediate and long races, which makes sense if the swim start, common to every format, drives the risk.

Injuries on the bike and in training

Few triathletes die on the bike from heart problems, but it is where the crashes happen: all 15 trauma deaths in the US series were on the bike leg. In short-course races, there were 20.1 medical presentations per 1,000 hours of competition. In one study of longer races, 10.8% of half-Ironman and 37.7% of Ironman age-group starters needed medical help, most of them in the later hours. Heat illness is a risk in long summer races.

Training brings the usual overuse injuries of runners and cyclists, plus swimmer's shoulder. Small prospective studies have found 10 to 24 overuse injuries per 1,000 hours of training and racing, depending on the month.

How to race a triathlon more safely

1. See a doctor first if you are over about 40, have heart risk factors, or have had chest pain, breathlessness or fainting on exertion.
2. Practise in open water in your wetsuit before race day, including in cold water, so the start is not a shock.
3. Start at the back or side of the swim and settle into an easy pace for the first few minutes.
4. Raise a hand or roll on your back if you feel unwell, and stop if you have chest pain or a racing heart.
5. Ride defensively. Keep your distance from other riders, especially on descents, and check the bike before the race.
6. Adjust for heat in long races: slow down, drink to thirst and cool yourself at aid stations.

How we scored it

Fatality risk (63) reflects about 10 micromortsMicromortA one-in-a-million chance of death. It lets you compare the risk of very different activities on one scale.More in the glossary per race, in the 5–20 band. Injury risk (70) counts bike crashes, heat and training overuse. Controllability (62) and rescue (80) both lose points in the swim, where hidden heart disease and poor visibility combine. Compare open-water swimming and cycling, the two legs that carry most of the risk.