AILSA CHANG, HOST:
One of the world's most grueling athletic endeavors is underway right now. The Tour de France began over the weekend under extremely hot conditions, which is a growing concern as climate change makes European summers hotter. Alejandra Borunda from NPR's climate desk is here to talk about the creative ways that riders are cooling down. Hi, Alejandra.
ALEJANDRA BORUNDA, BYLINE: Hey there, Ailsa.
CHANG: OK, so just how serious of a problem is heat in this race right now for the cyclists?
BORUNDA: Yeah, it's definitely a serious issue. The Tour is already a really hard race. It's more than 2,000 miles of cycling over three weeks in the middle of summer. The asphalt they're riding on can be 140 degrees.
CHANG: Wow.
BORUNDA: And some stages are won by milliseconds. And overheating - it can decimate riders. Like, this weekend, British cyclist Mark Cavendish threw up on his bike from the heat. And he almost fell to the back of the pack.
CHANG: Oh, my God.
BORUNDA: I talked with Julien Periard. He's a former triathlete-turned-exercise physiologist at the University of Canberra in Australia. He says everything feels harder when the riders are heat-stressed.
JULIEN PERIARD: What also happens when you're exercising in the heat because you have that increase in whole-body temperature is that your maximum power - your maximum aerobic capacity, or your VO2 max - your VO2 max kind of decreases progressively with hyperthermia.
BORUNDA: So to keep pedaling hard, a rider needs to send tons of blood to their heart. But to cool down, their blood needs to go toward their skin, where sweat or wind can cool it off.
CHANG: Oh.
BORUNDA: It's this competition within their own body.
CHANG: Wow - totally opposite directions for the blood to flow. Well, what do riders do to cool themselves down?
BORUNDA: Yeah. So the first thing is they start trying to acclimate for weeks before the race. Joao Correia is a former pro cyclist who's now the agent for a few guys in this year's Tour.
JOAO CORREIA: They'll do the rollers, you know, which is put your bike on a set of rollers that are stationary, and you ride that in either - in a hot environment, and then you go into a sauna afterwards.
BORUNDA: One rider a few years ago trained in his garden shed with the door shut and a heater on.
CHANG: Oh, my God (laughter).
BORUNDA: Yeah, I know. So what it does - this acclamation process - is it helps riders produce more sweat sooner. And it also makes their hearts pump more efficiently and their resting core temperatures drop. So they have more of a buffer when they're racing.
CHANG: OK, so I get how they prepare for heat ahead of time, but what do they do when they're actually riding?
BORUNDA: Yeah. So before the race, you'll see riders warming up wearing these, like, cute little ice vests. They're always in the shade with a fan blowing on them. And sometimes they - like, they shove nylon tights stuffed with ice down their jerseys.
CHANG: Ooh.
BORUNDA: And then, during the race, it's all about keeping wet because, when water evaporates off their skin, it takes heat with it. So they'll dump bottles of water over their heads. And they try to sweat perfectly.
CHANG: What?
BORUNDA: And by that, I mean trainers dial in a rider's exact hydration needs. So they'll figure out - I'm making this up. But it's like Tadej Pogacar, who's one of the best cyclists in the world - he'll need 1.83 bottles of water with 23 grams of carbs and electrolytes on this 12-kilometer stretch of a climb and help the bottles to do exactly that.
CHANG: Wow.
BORUNDA: Yeah. And this is fun, too. Some teams also have slushie machines. That's because it takes heat energy to melt ice. So a slushie cools them about three times more effectively than straight water.
CHANG: No wonder I crave slushies when it's super hot outside. OK, so has staying cool in cycling always been this technical?
BORUNDA: Definitely not. Correia told me that when he was first competing back in the 1980s, people thought, to adapt to heat, riders should drink less. Let's just say they're more sophisticated now. One of Correia's riders is Danish rider Matz Pedersen. Here's how he cools down.
CORREIA: We actually bought a van that is here with the team with an ice bath in it so that, you know, right after the stages, he has the opportunity to get in an ice bath when he's maybe waiting for the podium.
BORUNDA: They all really have to take this more seriously now because climate change is making European summers dangerously hot. Last year, the asphalt got so hot, Tour organizers had to spray water on the roads to keep them from melting.
CHANG: That is NPR's Alejandra Borunda. Thank you so much, Alejandra.
BORUNDA: Thanks so much.
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