Five men walk into the team conference room in Valencia and fill it with their physical presence. “Tractor”, “Tiger Shark”, “Iceberg”, “Frank” and “I just get Winston”. They are the powerhouses of Emirates Team New Zealand, otherwise known as the grinders.

Grinders are characteristically strong, silent types, the unsung heroes who are the engine driving their team’s quest to win the America’s Cup. Dean Barker is the skipper for Team New Zealand and Ben Ainslie, the British two-time Olympic gold medal-winner, waits on the sidelines to deputise for Barker as helmsman. To those roles go the recognition and glory, but an America’s Cup boat is like a human body and if the afterguard – the skipper/helmsman, tactician, navigator and strategist – are the brain, the grinders are the muscle. They change gears, lines and maintain and furiously operate the winches, sometimes hoisting six-tonne loads more than 100 feet.

Yesterday, they helped to produce the superior boat speed that beat Luna Rossa, of Italy, in the first match of the best-of-nine series Louis Vuitton Cup final. The winners will take on Alinghi, of Switzerland, the holders of the America’s Cup, this month. It is the ultimate test of match-race sailing – and fitness.

“If you don’t have the highest sailing skills, you’re just useless on the boat,” David Slyfield, the Team New Zealand fitness coach, said. “Rob Waddell [aka Iceberg] is an exception. Chris McAsey [Tiger Shark] and Winston Macfarlane [just Winston] had rowing backgrounds, too, but they had sailed a lot. The first boat that Rob sailed on was an America’s Cup boat.”

On some boats, the grinders are just hired muscle. DesafÍo Español, the Spanish boat, which lost to New Zealand in the Louis Vuitton semi-finals, had two firefighters in their crew whom they had discovered in a gym in Valencia last year. There are tales of crews recruiting bodybuilders who had brawn but were lacking in brain. So much so that crew leaders installed green and red lights to signal to their grinders when to start winching and when to stop. Many still got confused and sheered the sail from its bearings.

The New Zealand grinders are very competitive, even among themselves, and are revered throughout the fleet. “Iceberg” Waddell is known by opposition crews as the “Beast”. He is said to rival Matthew Pinsent for lung capacity. Slyfield, who trained him, suggested he try out for New Zealand.

“With rowing, it’s 2,000 metres, you are going for a maximum of 7½ minutes,” Waddell said. “You would never go that long in grinding. I would compare grinding to the hardest training for rowing, which were sets of flat-out 500 metres.” Grinders need strength, endurance and explosive power, taking the winch to more than 200 revolutions a minute. “It also helps if you have big ears and a small mouth,” McAsey added. They take their orders from the trimmers. “I’d compare the relationship to a [rugby] forward and a half back, there’s a lot of yapping,” Jonathan Macbeth (Tractor) says. “You have to learn how to take that.” Chris Ward (Frank, as in Frankenstein) said.

Only three heavyweight grinders are in the crew of 17 at one time. Waddell bulked up to 130kg (286lb) from his normal 105kg for the 2003 race, but is “only” 120kg now. The rules limit the crew to 1,570kg. Grinders eat 5,000 calories a day and spend a good portion of their time on a diet high on protein and carbohydrates.

Powerbrokers: Team New Zealand’s big men

Chris McAsey, aka Tiger Shark Age 34, primary grinder

A world championship rower, he was hired as a grinder in 2003.

Jonathan Macbeth, aka Tractor Age 34, primary grinder

Used to compete in triathlons and iron-man contests. Joined in 1997.

Rob Waddell, aka Iceberg Age 32, primary grinder

A world champion rower in 1998 and 1999, and 2000 Olympics gold medal-winner in single sculls. He joined Team New Zealand in 2000.

Winston “I just get Winston” Macfarlane Age 30, mainsheet grinder

A talented rower, built his credentials in match-racing around the world.

Chris Ward, aka Frank (enstein) Age 31, mainsheet grinder

Has been associated with the New Zealand team since the build-up to the 1992 regatta in San Diego.