A Sydney woman has become the first to complete seven marathons in seven days on seven continents in a wheelchair.

Johanna Garvin, 26, has some stories to tell after completing the gruelling World Marathon Challenge traversing Antarctica, Cape Town, Perth, Dubai, Portugal, Columbia and Miami.

"I saw it as an opportunity to challenge people's perception of what it is like to have a disability because it is such an unusual thing to do," she said a day after arriving back home in Sydney.

"It gives you the self-confidence that you can do different things in life."

So far she has raised more than $64,000 for the Cerebral Palsy Alliance but is aiming to get to $75,000.

While her team pushed her some of the way, Johanna helped with logistics. ( Supplied )

Johanna pushed herself in a specially designed wheelchair, but two seasoned marathon runners pushed her some of the way.

"The pushing itself, while it required a little bit extra effort, proved not to be our greatest challenge," runner James Alderson said.

"We had to go through customs, luggage check-ins then coaches to get to the race.

"When we were in Columbia we had to physically carry Johanna onto the [runway] and on the way out we had to go in a catering truck [that] was riddled with bullet holes."

Travelling through customs to the various locations proved to be one of the biggest challenges for the team. ( Supplied )

Even though she was pushed around the courses, Johanna was busy helping with logistics, particularly during night marathons.

"Because it was dark I had to point out where the runners were going and yell out to people to get out of the way," she said.

The trio took between four and five hours to complete each marathon, which proved especially problematic in the chill of the Antarctic when nature called.

"I tried to hold on as long as I could … by the end of the race I was busting," she said.

With her wheelchair-pushers exhausted, a group of Russians had to hoist her up into a facility.

Born 11 weeks prematurely, at just three days old Johanna suffered severe lung haemorrhage and a stroke which would lead to a diagnosis of cerebral palsy at the age of one.

After completing a Bachelor of Communications and Media, majoring in film and social justice at Sydney's University of Notre Dame, she works in communications for the NSW Government's arts, screen and culture agency Create NSW and is a budding filmmaker.