There were some "crazy theories", but doctors never quite figured out why Australian triathlete Richelle Hill spent three days in a German hospital.
Crowned under-23 world champion last October, Hill recorded an irregular heart beat after she had passed out during the bike leg and reported double vision and dizziness at Hamburg's mixed teams relay in July.
Tests cleared her of any heart issues and the 24-year-old is back on the start line fully fit and, despite the lingering mystery, trusting it won't happen again.
"I had been injured to start the year but I was feeling good for Hamburg and my body just shut down," Hill told AAP ahead of Sunday's Noosa Triathlon.
"I came out of the swim stumbling .... double vision, jumped on my bike and I was in and out of consciousness and next minute I was on the ground, looking up with people staring at me.
"In hospital there were some crazy theories but stress tests cleared my heart.
"It's still a big mystery for us and it plays on your psyche a bit, but we've had constant reassurance from doctors, who have confidence it won't happen again."
RICHELLE HILL TAKES THE U23 WORLD TITLE! 🌏🏆 One of the craziest of sprint finishes! The Australian 🇦🇺 leaves it VERY late to win the 2025 U23 World Championships in unforgettable fashion! #WTCFWollongong #Triathlon https://t.co/ELtgmX21gA
— World Triathlon (@worldtriathlon) October 16, 2025
Hill, whose mother Rina competed in the Athens 2004 Olympic triathlon, has finished on the Noosa podium in the last three years but never stood on the top step.
But winning on Sunday, or joining her mother as an Olympian at the 2028 LA Games, isn't a focus like it may have been a year ago.
"We have built it up from scratch again and ensured I'm the healthiest and fittest I can be," she said.
"I know I have the talent and the strength but I just need to focus on my own journey right now; I used to be really hyped up in what was around me.
"It takes a year to learn and I've gained so much this year, more than in a year of winning."
The women's field is wide open given 11-time champion Ash Gentle, who recently gave birth to her first child, is not on the start line for a second straight year.
Hill was second to Brit Jess Fullagar last year but the champion won't defend her title in 2026.
Paris Olympian Natalie Van Coevorden is arguably the woman to beat, returning to the 1.5k swim, 40km ride and 10km run distance after winning five 70.3 (1.9km swim, 90km cycle and 21.1km) races this year.
Van Coevorden boasts two Noosa podiums - in 2018 and 2024 - but no title.
Lotte Wilms, Charlotte McShane, Milan Agnew and Kira Hedgeland will also feature while Matt Hauser will defend his title as favourite in the men's event.
Meanwhile Callum Davies (14 minutes, 19 seconds) continued his winning run with victory in Saturday's 5km Asics Bolt, sprinting clear of Liam Cashin by two seconds.
Davies won the 1500m UQ Classic on Wednesday and last month's 10km Bridge to Brisbane road race.
Jaylah Hanock-Cameron (16:15) won the women's Bolt in a blanket finish while Liam Walsh and Alana Hribar cycled to the men's and women's Australian Open Criterium titles.
