Spending 24 hours in an industrial freezer in South Auckland may sound like madness to most people, but for transatlantic rowing champions Kevin Biggar and Jamie Fitzgerald the experience was crucial.

Next month the pair plan to do something no one has achieved - trek to the South Pole and back without assistance.

Part of their preparation was spending time in the freezer, which is the size of a basketball court, to test their equipment and to get used to extreme temperatures.

Emerging from the minus 22C freezer yesterday afternoon, Mr Biggar, who is 37, said spending time in the icy conditions was an important part of their rigorous training.

"We wanted to get in there and test all our equipment - all our clothing systems, our electronics, compasses, everything. Things behave differently in very cold conditions," said Mr Biggar, who lives in Howick.

The pair will tow a sled each, which will be laden down with high-fat food supplies and other essential items.

The sleds will weigh 160kg each and the men will cover a total distance of 2200km. The trek is expected to take about 70 days.

They will have to average about 20km a day and temperatures are expected to plummet to minus 40C.

The trek, known as the Thermal-Heart NZ Antarctic Expedition, is being funded through sponsors and will cost around $400,000.

The men hope to complete the journey in January next year, to coincide with the commemoration of the 50th anniversary of the founding of Scott Base.

The pair, who won the 2003 transatlantic rowing race from the Canary Islands to Barbados in record time, will begin their trek from Hercules Inlet in about six weeks.

"It's going to be painful but we are pretty excited ... The biggest challenge will just be doing everyday stuff without making a mistake. Everything will be so much harder because you are colder, you get sluggish, and because you've got big oven-mitts on your hands everything is harder."

It will also be the first all-New Zealand Antarctic expedition to the South Pole in 50 years.

Tauranga-born Mr Fitzgerald, 26, said he wanted to do the trek largely because nobody had done it without help before.

"We both have adventurous sides to our personalities. What better way to celebrate the 50th anniversary of the founding of Scott Base than to carry on the tradition of that adventurous spirit that New Zealand has?"

He said it would be important to keep their minds occupied during the trek.

"We will listen to audio books on our iPods about people who have gone through torment, wars and disasters. Then you think, 'This isn't so bad'."