six hours of running in full sun for a dozen volunteers, to study the resistance of our organism

Running for six hours in the sun probably doesn’t make you want to. Yet this is what 11 athletes endured on Thursday, July 20, at National Center for Defense Sports, in Fontainebleau (Seine-et-Marne). There is no medal for them, but they provide valuable assistance to scientists at the Institute for Biomedical Research of the Armed Forces (IRBA). These researchers are conducting a study to assess the impact of heat on the body.

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The decor is a bit repetitive: a one kilometer loop with a refreshment point between each lap. “For example, Vincent, who is coming, asked us for watermelon and sparkling water. For the study, we note everything they ingest, the liquid and the solid. We weigh the quantities and at the same time, we take their time to see if they manage to keep their pace throughout the event”describes one of the organizers of the experiment.

Nothing is left to chance. These data will then be analyzed by IRBA scientists. Their mission is to understand how the human body adapts to extreme temperatures. Weather conditions are reproduced in the forest of Fontainebleau, according to chief physician Pierre-Emmanuel: “It’s not the Sahara, but it nevertheless corresponds to temperatures that we are increasingly confronted with with global warming. Today, they run on a tarmac track. So it is around 25°C outside, but the radiation reaches 40°C in certain places”.

On arrival, after six hours of effort and nearly 70 kilometers covered, it is the heat stroke for some athletes, forced to lie down, a wet towel on the forehead. Head doctor Cyprien observes the scene: “They have a sensation of dizziness, dizziness. There, we must let them rest quietly, then they will finish the tests and we will take a short trip to the swimming pool!’

Blood tests and thermal cameras

Nils is one of the participants in this experiment. His specialty is trail running, long distance races: “More than ten hours of racing, in the mountains. It goes up, it goes down, the rhythms are varied and we stop at the aid stations to eat. Today it was six hours with the only breaks being the weigh-ins. Otherwise, we ran all the time. It’s a very different effort from what I’m used to doing”.

Hardly time to breathe that it is necessary to chain the tests: blood test and thermal cameras. For her part, Audrey, French champion of the 100 kilometres, completes the cognitive test: “On a computer, we are asked how we feel. How do we feel thermally, do we manage to feel our heart rate, what are our food cravings…”

For army doctors, this information will eventually make it possible to adapt military rations for soldiers on overseas operations or to prevent heat-related pathologies.