The Hawkesbury to Harbour endurance challenge is to raise money for international charity organisation Oxfam.

Ms Linsen, 38, will be joined by team-mates Julie and Craig

Donnell and Alex Zimbounellis, with whom she has been training since March for the 48-hour event.

The group has steadily increased its training and walked 57 kilometres in 16 hours recently.

Ms Linsen said the chance to raise money that will help people in crisis sleeping rough on the streets around the world as well as in Australia, at the same time as getting fit and challenging herself attracted her to the event.

``We decided to take on the challenge to get fit and be great role models for our kids,'' she said.

``It has been a pretty full-on few months of training and planning but a great journey in many ways.

``I feel as fit as I was 20 years ago, which is nice, and we have discovered a whole new side to Sydney that we didn't know existed.

Ms Linsen's team will raise about $6000 for the charity and is just one of 500 groups of four taking part in the challenge that is expected to raise an estimated $2.5 million.

She said the money will be used by Oxfam to fund programs across the range of services it provides to help people in crisis such as the floods in Pakistan and work in remote Australian Aboriginal communities.