AFL legend and broadcaster Kane Cornes will put his body on the line for sick WA children by running two marathons in the space of just five days.

The Telethon ambassador will run through the streets of Perth on Sunday as he takes part in his first Perth Running Festival marathon.

The sold-out event is renowned for having one of Australia’s most scenic marathon courses.

Now in its third year, the Perth Running Festival has raised more than $600,000 for Telethon in the past three years.

Only four days later Cornes will run 42km — the equivalent of another marathon — around Rottnest Island.

To make the experience even tougher, there will be some extra challenges thrown in along the way.

While Cornes is an accomplished distance runner — with several marathons and a 725km ultra-marathon for charity under his belt — even he admits he’s a little unsure about whether it was entirely sensible to sign up for such a gruelling week.

“Two marathons in five days seemed like a reasonable idea at the time,” he said.

“I’m less sure about that now, but I’ll be at the start line.”

But the former Port Adelaide midfielder and Seven commentator remains adamant that it was too good a cause not to say yes.

“Telethon is unlike anything else in this country,” he said.

“I’ve seen what it does for kids and families in WA, and once you’ve seen that up close you want to find a way to help.”

Cornes said he had kids of his own and he did not take their health for granted “for a second”, so he was willing to step up to help fund vital programs, services, equipment and research for children who were not so fortunate.

“There are families across WA whose children are doing it tough, and Telethon is there for them when it matters most,” he said.

“If putting myself through a bit of pain gets more money to those kids, that’s an easy decision.”

During the inaugural Rotto Run for Telethon, Cornes will be joined by a team of familiar faces — including Premier Roger Cook, AFL great Luke Hodge, Triple M breakfast hosts Xavier Ellis and Katie Lamb and beloved mascot Fat Cat — as they complete a series of mini-challenges.

Instead of simply running from start to finish, the group will face unexpected tests along the way to help boost the fundraising total.

The Premier will slog it out alongside Cornes for 10km of his island circuit — as well as tackling the 10km event at Perth Running Festival — while Hodge will take the ultimate leap of faith by skydiving over the island.

Lamb and Ellis will chase Cornes down on a rickshaw and an electric bike, as well as broadcasting live from Rottnest as the fun unfolds.

Supported by CommBank Business Bank, each challenge will put the teams to the test, with every completed challenge providing another chance to raise money for Telethon to support WA kids.

Cornes said people could get behind the events by taking on the challenge with him.

“You don’t have to run 42km — set yourself a challenge, whatever that looks like, get your mates or your workplace behind you and raise a few dollars for Telethon,” he said.

The total amount raised from Cornes’ marathon double will be revealed at the Telethon weekend two days later, on October 17 and 18.

Some of Australia’s biggest music, television and sporting names have been locked in to appear at RAC Arena for the annual 26-hour celebration honouring WA’s sick kids.

West Australians wanting to support Cornes’ efforts can donate to Telethon at telethon7.com/rottorun