Ten-time Ironman New Zealand champion Cameron Brown is going to put the theory that life begins at 40 to the ultimate test this weekend.

Brown will make his 12th start in arguably sport's toughest test in the Ironman World Championships in the cauldron-like heat of Kona-Kailua on Hawaii's Big Island on Sunday (NZ time).

After indifferent performances over the last three years, Brown is keen to ensure his likely last showing in Hawaii is one he is proud of.

He heads a group of 33 New Zealanders who have qualified for the world championships, with Jo Lawn (Auckland) and Gina Crawford (Christchurch) joining him in the pro elite division. The remaining 30 will compete in the age group divisions from outstanding 25 year old prospect Larisa Marsh to the remarkable 75 year old, Neil Fleming (Taupo).

Also back is Kumeu's irrepressible Tiare Lund, who will defend the 65-69 years age group title, and Auckland's Hilary Wicks, third last year, who steps up to the 35-39 years category.

"If it is my last time here then I want it to be a bloody good one," said Brown, who enjoyed four podium finishes in Hawaii from 2001 to 2005.

Accordingly the father of two left the family behind for eight weeks of hard training at altitude in Boulder, Colorado.

"I wanted to give it one last hurrah and go somewhere that was a little bit hotter. I had one day of rain and temperatures were over 32C deg. There's great trail running and endless 20km climbs riding."

Brown even ventured to Winter Park, high in the Rockies, where famed world champions Scott Molina and Mark Allen went for key sessions.

"I got in some real high altitude training. I did one run at over 3100m (10,300ft) that was a lung burning run.

"I have had a solid eight weeks of training at altitude that has been fantastic with no interruptions. Then the altitude effect which has allowed me to push a bit harder. Hopefully I should be firing on all cylinders on Saturday."

He knows the race is about performance on the day.

"The world champions have all said that you have to feel absolutely brilliant on race day if you want to win this thing. I have never really had that feeling.

"It is very hard here with the conditions and when you are racing the world's best. You only have to be that little bit off and you will get beaten, and well beaten at that.

"If you are out of the water down and you are not a super-cyclist, then your race is done. It is so important for me to have a good swim so I can be up there on the bike, and be with Craig (Alexander) and Chris McCormack on the run.

"Hopefully I can put it all on the line, go well, feel good throughout the whole 180km bike ride and get off and run well."

Favourites are Australians Alexander and kiwi-born McCormack who have won the last five times in Kona between them.

Both Lawn and Crawford come into the women's race in outstanding form in a field that is not as deep as in previous years.

Lawn has enjoyed three finishes in the top five in Kona and comes off an impressive fifth place in the Ironman 70.3 world championships in Las Vegas, while Crawford's performances have been nothing short of remarkable since the birth of her son Benji. She won two Iron distance races including Wanaka, was second in Ironman France and fourth in European long distance championships.

The elite race starts at 5.45am on Sunday (NZ time) with men's winner expected by 2pm and women by 3pm.

The New Zealand team is:

Pro Elite: Gina Crawford (Christchurch), Joanna Lawn (Auckland), Cameron Brown (Auckland).
25-29 years: Larisa Marsh (Auckland), Erin Furness (Hamilton)
30-34 years: Anna Ross (Auckland), Andrew Black (Christchurch), Helen Kay (Auckland).
35-39: Jarrod Newell (Auckland), Hilary Wicks (Papakura), Gigi Green (Auckland), Scott Hotham (Auckland), Armando Galarrga (Auckland).
40-44: Jamie Hunt (Auckland), Jeff McGrath (new Plymouth), Phil Richards (Drury), Kim Dorling (Auckland), Sandra Boubee (Tauranga).
45-49: David Craig (Wellington), Aimee Perrett (Feilding), Robyn Gutry (Hamilton).
50-54: Mark Burke (Wellington), Sue McMaster (Palmerston North).
55-59: Debbie Clark (Tauranga), Andrew Davidson (Auckland), Graeme MacDonald (Whangarei), Brett Mudgway (Napier), David Moriarty (Havelock North), Kingi Smiler (Wellinton).
60-64: Alan Fletcher (Manukau), Shirley Rolston (Christchurch).
65-69: Tiare Lund (Kumeu).
75-79: Neil Fleming (Taupo).

For full details and live streaming, see www.ironman.com.