Switzerland's Jolanda Neff, the reigning Cross-country Olympic champion, resigned her spot for the Paris Olympic Games, according to the Swiss Cycling Federation.
Marlen Reusser, the silver medalist in the Tokyo Olympic Games individual time trial, also announced on Monday she would not be competing in this year's Olympics in Paris because of a lingering illness.
Neff has struggled with breathing issues for several years and speculated her ailment could be related to repeated COVID-19 infections.
"As soon as I go hard, the system explodes and I can't breathe anymore," Neff told SRF in late May. "I can only gain a little time on technical sections and then just ride at my own pace on the climbs. That takes so much patience and it's extremely frustrating. In Nove Mesto, the pace was so high very early on that I completely exploded. I couldn't breathe at all.
"I've had the same problem for four years. I don't know what it is, but I can't get much air when I breathe. I've had corona[virus] three times and I don't know if my lungs have been damaged in any way as a result. I've also had severe hay fever since 2016. I had that more or less under control."
Neff has been diagnosed with exertion-related constriction of the vocal cords and while she has undergone therapy to treat the condition, she is not ready to compete at the Olympics.
"I would prefer it if someone else went. I don't have to go to the Olympics to come last. I only want to take part if I can perform," Neff said in May.
Sina Frei, the silver medalist at the 2021 Games in Tokyo will take Neff's place, racing with Alessandra Keller. Switzerland is currently the top-ranked nation in the UCI Cross-country rankings for both elite women and elite men, with Keller leading the individual standings for elite women.
Reusser said she "suffers from a so-called post-infectious syndrome caused by a viral infection" in a post on social media saying it is unclear what caused the syndrome which has forced her to stop training.
"In February, I suffered from a COVID infection," Reusser said. "Then a fall in the Tour of Flanders and I had fractures to my face and teeth. An operation and several viral infections in May and I still haven't recovered."
According to her SD Worx-Protime team, Reusser has been subjected to numerous examinations, had a tooth extracted, taken antibiotics and more, but has not improved enough to compete in Paris.
"I saw a lot of doctors, had a lot of tests and still always had the hope that I would be fit in time for Paris.
"A significant part of my treatment now consists of rest, so I have to plan and hope for the longer term and do everything I can to ensure that I can compete in top form at the World Championships in Zurich.
"It remains to be seen whether that will work but I will certainly do everything I can."
Reusser will be replaced by Elena Hartmann in the time trial and road race in Paris, joining Elise Chabbey, Noemi Rüegg and Linda Zanetti in the Swiss Olympic road team.
