PM Abbott leads children's health campaign

Prime Minister Tony Abbott has traded his bicycle for walking shoes as part of a campaign to increase the amount of exercise Aussie children are doing.

Mr Abbott led primary school students on a walk around Sydney Harbour on Friday morning for the launch of the Murdoch Children's Research Institute's Step-a-thon.

"I'm so pleased today to be encouraging healthy exercise and supporting medical research, because both of these are essential if we are going to make the same sort of advances in our lives over the next 100 years that we have in the last 100 years," he said.