World Triathlon says the partnership is designed to "benefit the entire World Triathlon movement",, external with new opportunities to engage athletes and audiences, and a stronger platform to grow triathlon and multisport from grassroots to elite level.

The question for athletes is, how?

European champion Roksana Slupek, of Poland, said she was "not against the idea", but wanted more information.

"What's the benefit for us, for triathlon? It's nothing against Hyrox," said Slupek.

However, Stapley called the move an "attack on our whole existence" and is concerned that World Triathlon could direct attention and resources towards Hyrox's Olympic ambition - at the expense of his own sport.

"How does Hyrox grow triathlon? If anything they've killed triathlon," he said, while also suggesting brands would rather get in early with Hyrox athletes before they potentially appear at an Olympics.

"Sponsorships have reduced because there's no visibility on TV, you have to pay to watch us.

"We are triathletes that do the short distance, which is the Olympic distance, and we've trained all our lives for it.

"There's no swimming, there's no biking, it's indoors. [Hyrox] has got nothing to do [with triathlon]".

"It seems like our sport's gone, 'no worries, come along, use our structure, use our access to the International Olympic Committee, and perhaps take our space'.

"We've got an opportunity to win medals in Los Angeles [at the 2028 Olympics], but will we have it further down the track?"

Evans said that while triathlon was an "established" Olympic sport, that has provided high quality racing since its introduction to the Games 26 years ago, this new partnership has introduced a "level of uncertainty".

"A lot of the resistance has come from athletes, because you don't know," she added.

A World Triathlon spokesperson told BBC Sport, it is continuing to "increase its focus and involvement in the Olympic and Paralympic families" and that it is in the "planning phase" for Brisbane 2032, adding that "triathlon is, and will remain, at the heart of everything we do".

BBC Sport approached Hyrox for comment, but they referred us to the statements made by World Triathlon.