The 23-year-old won more gold medals than any other athlete at London 2012 but will be absent in Brazil.

The Northern Star newspaper, based in New South Wales, Freney's home state, has claimed her decision not to enter this month's Australian Championships, the trials for both the Olympics and Paralympics, is due to a "medical mystery problem". 

It follows her decision to also withdraw from last year's International Paralympic Committee Swimming World Championships in Glasgow due to the illness. 

Freney, who has cerebral palsy, has been suffering from electromagnetic sensations triggered by strenuous training, and extensive tests have failed to solve the issue, the newspaper reported. 

Freney, voted the 2014 Young Australian of the Year, is trying to remain positive, despite the setback, and is hoping to concentrate on other things in the near future. 

"I don't think I have anything to prove in my swimming now," Freney, winner of three Paralympic bronze medals at Beijing 2008, told The Northern Star.

"I'm taking it as a sign the universe doesn't want me to go to Rio [2016].

"I'm doing it all backwards.

"I'm picking up the areas lacking when I committed myself to eight years of hard training."

Freney, however, claimed this did not mark the end of her swimming career.

"It's a little bit disappointing [not to be going to Rio]," she said.

"If the sensations go tomorrow, I'm quite happy to get back in and train and hopefully compete.

"I am not in retirement phase."