Australian footballers have turned Hyrox champion Joanna Wietrzyk's mid-race bowel accident into a Mad Monday costume, posing in crop tops with brown smears down their legs.

Online snaps show men wearing black exercise gear and homemade Hyrox signs in an apparent imitation of the Australian athlete, whose ordeal during a Beijing race attracted worldwide attention.

One posed with a beer and raised a finger while wearing a black headband, with a handwritten sign clipped to his top.

The photo carried the words 'SPRAYGUN ON MAD MONDAY'.

Another showed a smiling man standing in a bathroom beside a wet floor sign, wearing a similar outfit with brown marks covering parts of his legs.

The players' names and clubs have not been established.

The costumes drew approving responses from some social media users, with one predicting the look would become a popular choice for Halloween.

'Someone had to do it,' one person wrote.

'$5 says there'll be more spray bums than rayguns this Halloween,' another commented.

'That's gold u win the Aussie internet for today,' a third added.

Another wrote: 'Knew this would be coming, and absolutely here for it.'

The photos add another chapter to an incident that has prompted an apology from Wietrzyk, the forfeiture of her victory, and changes to Hyrox's competition rules.

The Melbourne athlete continued competing in Beijing after suffering a bowel accident, completing exercise stations with faeces visible on her legs.

She crossed the line in one hour, one minute and 23 seconds and was initially declared the winner.

But footage of her continuing to use shared equipment sparked criticism of both her decision to keep racing and the organisers' failure to intervene.

Wietrzyk subsequently apologised and announced she would retrospectively withdraw.

'I want to offer my sincere apology to the people of China, my fellow competitors, the spectators and the HYROX organizers for what happened during the race in Beijing,' she wrote on Instagram.

'I felt completely fit and healthy at the start of the race, with no reason to expect any illness. Looking back, I regret the decision to not have stepped off the track.'

She acknowledged that continuing had affected others.

'I recognise that I should have made a different choice. I take responsibility for my decision to continue and am deeply sorry for the discomfort and disruption it caused.'

Wietrzyk confirmed she would surrender the points earned from the race and take time away to recover.

'I will be taking some time to recover, reflect and look after myself and my family away from the noise,' she wrote.

Hyrox co-founder Moritz Fürste also accepted that officials should have acted.

'Hyrox made a mistake by not reacting immediately to the incident,' he said.

The updated rulebook allows athletes to be withdrawn on medical grounds when blood, vomit, urine or faeces pose a welfare or contamination risk to themselves or other competitors.

The sport combines eight one-kilometre runs with workout stations including rowing, sled pushes, burpee broad jumps and wall balls.

Questions about hygiene have been accompanied by concern over the personal impact of the public scrutiny.

Former professional triathlete and Ironman champion Bec Hoschke told SBS News the situation involved the wellbeing of Wietrzyk as well as the safety of those competing alongside her.

'I can't imagine the mental impact all of this is having on someone. I think she's only in her early 20s as well. It's enormously confronting for someone to have to deal with at that age.'

Wietrzyk thanked those who had offered support as she dealt with the fallout.

'Thank you to those standing by me, both as an athlete and as a person, during this time, and to everyone who has reached out with kindness and support.'