The first time Maeve Plouffe trained in the heat, she was in Paris in the lead-up to the Olympics. It was supposed to be an easy ride to help get used to the conditions. When she returned, she fainted from heat sickness.

“That’s how badly I was affected,” she says. “Racing in extreme heat is like playing chicken with your environment.”

What was once a speciality has now become standard, the Australian Olympic cyclist says, especially ahead of big races such as the Tour Down Under that are known for intense conditions. Training starts a month in advance, up to three times a week, and takes place in a glass box roughly the size of a small conference room within the South Australian Sports Institute.

Sessions run for an hour, during which the chamber is heated to between 36C and 40C to simulate riding for extended periods in extreme heat, in service of mentally and physically preparing competitors for extreme conditions.

“Racing in it feels like your whole body is encapsulated in heat,” Plouffe says. “Everything just deteriorates so fast and there’s no relief from it.”

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Cycling as a sport is particularly vulnerable to its environment, especially as climate change pushes extremes to grow more intense.

That reality is beginning to force an uneasy conversation within the sport about its relationship with fossil fuel producers such as the Australian oil and gas company Santos, sponsor of the Tour Down Under, which begins on 16 January.

Santos has held naming rights to the race since 2010 and renewed its relationship in January last year, giving it the rights until 2028. It has faced protests and calls for divestment and dissociation, particularly after the 2019-20 bushfires.

Riders themselves are increasingly uneasy about the relationship. Plouffe, who holds degrees in law and marine biology, does not criticise Santos or the race organisers directly but says the next three years give organisers time to plan the race’s future.

“I think it will just resonate better for a lot of people involved if there was an option to have a different sponsor of the event,” she says.

Brodie Chapman, the former national road champion, agrees.

“It’s certainly time that the Tour Down Under considers a new sponsor to more align with the values of the modern world, the Australian people, the natural world and athletes,” Chapman says.

The former national champion Cyrus Monk says it is “embarrassing” that Santos sponsors the biggest race in Australia.

“I’d love to see another sponsor to be able to step in,” he says.

Monk says it is often assumed another sponsor would be difficult to find, but it is not clear this is true. Race organisers and Santos have not been transparent about how much the company pays for naming rights, nor how much the South Australian government kicks in.

“Obviously the dream would be similar to the [Belgian] Renewi Tour, where the sponsor is a renewable energy company that is doing something better for the environment,” Monk says.

Santos has not responded to questions but a spokesperson for the Tour Down Under praises the company as a “valued naming rights partner”, saying “without their support we would not be able to deliver a world class international bike race”.

“Their support has enabled our event to grow which has seen the introduction of a women’s WorldTour race with equal prize money to the men, and the TDU being recognised as Australia’s best sporting event in 2024,” the spokesperson says.

The spokesperson says “natural gas produced by Santos plays an important part in South Australia’s world-leading investment in renewable energy, and its carbon capture and storage project at Moomba decarbonising the equivalent of 700,000 cars off our roads each year” – an argument that has also been echoed by the South Australian premier, Peter Malinauskas, and the company.

Neither Santos nor race organisers have responded to questions about whether the company helped draft the Tour’s response.

Earlier this year, Santos received approval for its Barossa gas development, considered one of the dirtiest gas projects in the country. The Moomba CCS project has so far been able to capture just 4.6% of Santos’s total corporate emissions, according to one analysis.

Matt Rendell, a former Tour De France commentator who has been working with the Badvertising campaign, says the economics of cycling have made the sport “an unexpected locus of this rearguard propaganda activity by the fossil fuel industry”, and the way contracts work means athletes often are not free to raise concerns.

“Cycling is cheap and the bicycle has impeccable environmental credentials,” Rendell says. “These companies want to associate themselves with cycling because it allows them to associate themselves with the environment, the photography, the imagery, the dream of the wilderness and peak physical human performance.”

There is also a complex relationship between races and the cities that host them, he says, with race organisers reliant on the goodwill of local authorities for access to roads and public infrastructure.

Santos is the biggest company with headquarters in Adelaide, underlining the race’s South Australian identity.

Similar battles over fossil fuel advertising are playing out in Europe over the Tour De France’s relationship to Total and Ineos. Rendell says the Tour Down Under represents an obvious flashpoint, given it is held in a place “where cycling comes into contact with extreme weather”.

“Cycling works on the imagery of the man against mountain. It’s a David and Goliath scenario, but that’s also the struggle against the continued poisoning of the atmosphere,” he says.

The assumption that no other sponsor could be found is “a failure to imagine things otherwise”, he says.

“In the simplest terms possible: whether it’s Santos or someone else, as long as you are locked into a sponsor, you’re not out looking for other sponsors. As soon as there’s doubt, that changes.”