She received a late call-up by Athletics Australia on Monday after the withdrawal of national 20km champion Tanya Holliday.

Ruddick said she had burst into tears on getting the news.

"It's emotional, that's for sure."

This will be the highlight of the Ballarat 42-year-old's athletic career.

She will be one of three Ballarat representatives in the Australian Flames racewalking squad, joining brother and sister Jared and Rachel Tallent.

Rachel Tallent and Ruddick will be two of Australia's three competitors in the 20km event on August 28.

Jared Tallent is chasing another world champion medal in the 20km and 50km.

Ruddick’s selection also enhances her hopes of  competing in the 2016 Rio de Janeiro Olympic Games.

Ruddick began the new year on target to earn automatic selection for Beijing.

She produced two qualifying times and had the form to meet the automatic selection requirement of a top three finish at the nationals in Adelaide in February.

However, she suffered calf trouble in the event and could only manage fourth after stopping several times.

"I thought that's it. It's over.

"I was resigned that I wouldn't be going (to Beijing).

"Then this comes."

Ruddick said her selection was a reward for a big team effort by family and supporters.

Ruddick, who has represented Australia in Mexico and China (twice), will spend a week with the team preparing in Japan on the way to China.