But that's just what Katie Visco and husband Henley Phillips are attempting during their latest fitness adventure.

The pair passed through Katherine yesterday on there way down south.

Running an average of 42 kilometres a day, while Henley pedals alongside with all their worldly possessions, they reckon they make the southern coast in 20 days.

"It's not for everyone," the super-fit Katie admitted.

"We are trying to encourage people to follow their biggest dreams, as we are trying to do."

Katie has form in these seemingly impossible runs.

A decade ago, she ran east west across the US.

The Montana pair said they had been eyeing off the challenge of running north-south in Australia for many years.

Hills are a major obstacle, she admitted.

"Henley struggles on the bike more than me going up but then he can coast down."

Henley is lugging a lot of water on their trek, so riding is no easy feat either.

You can support their ambitious effort by heading here.

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