How Tour de France cyclists are handling the heatwave

In the final minutes before the hottest stages of the Tour de France, the man in the yellow jersey, Jonas Vingegaard, can be spotted wearing a cryovest – a fetching waistcoat of ice. Keeping his body temperature low delays the inevitable spike, at least a little, and as soon as the race is done he cools down in front of an industrial-sized fan while a staff member douses his neck with freezing water.

The south of France has been punishingly hot in recent days. Temperatures reached 39C and a weather warning was issued across regions including Alpes-de-Haute-Provence, where the Tour is into its third week of hard racing. The road surface a few inches below the riders’ feet is a burning 60C, cooking riders like a pizza oven. Cyclists may be anatomical anomalies but they race on their limits, and the inescapable heat can break them.

Inside the peloton, ice cubes are crammed in helmets and stuffed down jerseys and specially designed socks. Chilled bidons are pushed down backs, and wet towels are wrapped around shoulders. Britain’s Tom Pidcock wears his own cooling jacket made up of 20 individual pockets. On the road, they snake across to the side guarded by trees or a few shop awnings, and afterwards team doctors assess weight loss, as well as their urine.

The area to make marginal gains has shifted through phases over the years: the focus was body fat percentage, diet and nutrition, sleep (Team Sky would take a rider’s personalised bedding to each new hotel); key data points like functional threshold power and Vo2 max; improvements in aerodynamics and altitude training. They remain relevant but, increasingly, heat adaptation is becoming a critical tool in a rider’s armoury.

Vingegaard’s closest rival, Slovenia’s Tadej Pogacar, has a reputation for struggling in the heat, while oddly Vingegaard – who grew up in the much flatter relief and cooler climate of Denmark – thrives on hot and sticky days in the high mountains. Pogacar took special action this year, training in Spain’s Sierra Nevada desert where he wore extra layers of clothing to stress his body, and deliberately limited nutrition and water intake to replicate the depletion of a burning day.

Taking onboard enough energy before and during the day’s race is vital. Elite riders train themselves to eat as much food as possible, literally stretching their stomachs, in what is another secret discipline within the sport. When they can’t take on more, it can be costly. “I need to evaluate a little bit, but I think I just didn’t have enough energy,” said Ineos’s Tom Pidcock after losing valuable time on the mountainous stage 14 due to heat exhaustion. “Yesterday was a late stage, a late dinner and I just couldn’t really eat enough.”

Sodium replenishment has become an industry in itself. One company, Precision Fuel and Hydration, works with Belgian team Lotto-Dstny to come up with tailored fueling strategies, based on each rider’s rate of perspiration and their sodium lost per litre of sweat. Beads of sweat are sucked up from a contraption on the arm and analysed carefully: everyone sweats differently (it has nothing to do with fitness or aerobic capacity) and so everyone’s fueling needs are unique.

It all feeds into the body’s ability to respond to a rising core temperature. I recently put this to the test in the Porsche Human Performance Centre at Silverstone, by riding a watt bike for 30 minutes in a heat chamber set at 40C, to get the smallest sense of what a Tour de France rider might experience. Even in that short period of time, at a manageable cadence, the heat was smothering and the legs felt noticeably drained.

My core temperature was measured throughout the experiment to make sure it didn’t tip above 40C, at which point the test would have been abandoned. Below 38C the body can operate with high efficiency, but once a rider’s temperature tips above 39C, the brain instructs the muscles to slow down and fatigue sets in. Above 40C, heat exhaustion (losing too much water and sodium through sweat) is in play; above 41C there is the serious risk of heat stroke (when temperature-regulation fails) and the body shutting shut down.

My temperature got very close to 40C before stabilising in the high 39s. Stepping off the bike and out of the chamber half an hour later brought a wash of relief.

Tour riders have an arsenal of tools to prepare for such extreme conditions, but ultimately there is only so much they can do once they hit the road. There they are exposed and they have no choice but to ride through the heat. There is a balance to be struck between conserving output and pushing hard: the quicker they finish, the quicker it’s over.

Then again, for Vingegaard, the harder the race and the tougher the conditions, the more chance he has of winning another yellow jersey. After two-and-a-half weeks of gruelling racing, from the sweeping coastline of the Spanish Basque Country to the high Alpine roads, through driving rain and stifling sun, he is almost there.