It was a tough weekend for Dutch road running. At marathons in Groningen, Utrecht and Amersfoort on Sunday, several runners collapsed from heat-related problems despite seemingly modest temperatures, and a week after the marathon in Maastricht was cancelled outright because of the warmth. Experts and organisers say even moderate heat, combined with humidity and racing pace, can be dangerous.
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Around 12,000 runners took part in the 10 km, half marathon and full marathon races in Groningen on Sunday, the first time the city has hosted a full marathon through its centre. The main race started at 10:30 am, and by early afternoon emergency services were treating seven runners for heat-related problems, all with symptoms of heat stroke, according to the Veiligheidsregio Groningen. Two of them were taken to the UMCG hospital.
Most of those affected were running the half marathon. As cases came in from different parts of the route, the safety council scaled up to GRIP 1, the level of emergency coordination used when several services need to work together, and called in ambulances from Friesland and Drenthe. The fire service deployed special mist installations, normally used during large fires, to help cool runners. Spectators were asked not to travel to the city centre to keep emergency routes free.
The temperature in Groningen at midday was around 21 to 22°C, lower than at events earlier in the spring. A Red Cross spokesperson said the issue was the combination of high humidity and strong sunshine, which made the conditions far more taxing than the thermometer suggested. The organiser also said the temperature came out higher than originally forecast.
In Utrecht, where the Dutch national half marathon championship took place the same day, one runner collapsed and was resuscitated on the route. They were flown to hospital by trauma helicopter, with the race briefly halted while the medical team arrived and other runners were guided past. The marathon itself was not cancelled. In Amersfoort, two more runners were treated for heat-related symptoms.
The weekend follows a more drastic step a week earlier. The Maastricht marathon, the 42.2 km race of the Long Course Weekend, was cancelled outright in advance because of forecast temperatures around 30°C. Around 1,000 marathon runners were automatically moved to the half marathon, whose start was brought forward 1.5 hours to 8:30 am, and a Drenthe running festival in Klazienaveen was also cancelled. Earlier in the season, the half marathon in Zwolle was scrapped for the same reason.
Maria Hopman, professor of integrative physiology at Radboudumc, told NPO 1’s “Goedemorgen Nederland” that the figures should not surprise anyone. “There’s nothing wrong with running in the heat in principle. But in a race, pace plays a big role. People are less likely to ease off voluntarily.” Most cases on Sunday occurred in half marathons, she noted, where amateurs often push for personal bests. “On days like these, that’s disastrous. You go looking for your body’s limits. The body produces a lot of heat at such a moment, and during running it has trouble getting rid of it.”
Heat stroke, Hopman said, can occur at “any temperature,” with the risk rising sharply with humidity. Her suggestion for organisers: start races earlier in the day to keep ahead of the heat.
For amateur runners signing up for the next event on the calendar, the practical message is much the same as the one organisers handed out at the water stations all weekend: drink, slow down, and listen to your body.
