KEY POINTS:
The temperature is close to boiling point, your eyes are burning with salt, your lungs screaming for air.
You have already completed 30 gut-busting tacks and it is only the first upwind leg. Worst of all, your opponent is breathing down your neck. A slow tack now and it could be game over.
Grinding may not be one of the glamorous jobs in the America's Cup but, in a very real sense, the grinders are the engine of the yacht - powering the winches that reel in the sheets and halyards during sail hoists, tacks and gybes.
The job requires explosive bursts of energy. The highest handle speed while grinding in a sailing manoeuvre is around 200rpm. The heaviest load on the headsail-sheet that a grinder is required to grind in is four tonnes
"You can have an easy race, especially in Valencia where there is light air. If the boats aren't close or we aren't covering too tightly, you might only put two or three tacks in up the beat. That is not too hard at all," said Emirates Team New Zealand grinder Chris McAsey.
"At the other end of the scale, if we are covering closely and it is blowing hard at the same time, it is just heinously tiring."
McAsey is one of five grinders at Team New Zealand. A big burly group whose arms are the size of tree trunks. Like his prominent team mate Olympic gold medallist Rob Waddell, McAsey was a competitive rower.
He made the New Zealand junior rowing team while at school, Wanganui Collegiate, then went on to represent New Zealand at the 1994 and 1995 world rowing championships in the fours and eight, winning a silver medal in 1994 in the coxed four.
He was a member of a New Zealand eight who failed to qualify for the 1996 Olympics in Atlanta.
"We had to go to Switzerland to a qualifying regatta and get first or second. We had a bad race and were out. I had set my goal on the '96 Olympics, that's all I cared about and when that didn't happen I thought 'what is next, do I carry on or quit?"'
In 1995 McAsey's interest in sailing was sparked watching Team New Zealand compete in San Diego.
"I was training out at Lake Karapiro, I'd get home from training and see those guys do their thing at San Diego and thought it looked pretty cool and decided that I wanted to get into that sort of thing.
"All I knew about the team is what I saw on TV, they went out and won every race and just seemed unbeatable. The team aspect is what I liked about it. It's still what I like about it."
He started sailing in 1995 during the down season from rowing, in cruising boats and did some (of the Royal New Zealand yacht Squadron's) rum races. After 1996 he stopped rowing and did more sailing.
Desperate for a job with Team New Zealand he "kept throwing them my CV."
"I never really got a look in till after the 2000 cup when a few guys left and a few spots opened up. I had been banging on the door since 1997.
"Grinding, that's what I'd set my sights on and that is what I am doing till I get a job on the helm," he jokes.
The physical nature of grinding means plenty of time is spent at the gym.
In non-racing periods that can mean up to nine sessions a week.
Then there is their diet.
"We are pretty much eating as much as we can," McAsey said.
Which is pretty rough on some of the other crew members who have to keep their weight down to compensate for the grinders so that the crew can weigh in under the 1570kg limit.
"Behind our backs they probably give us plenty of flak," McAsey said of his lighter team-mates.
"If anyone was going to give us flak, it would be the trimmers but if we were a little less strong their job wouldn't be so easy, we make them look good, basically."
McAsey said there were similarities between rowing and grinding.
"When you row, you get to the last 500m and all your muscles are screaming out, full of lactic acid.
"When you get in a tacking duel, it is that same feeling. Your body wants to stop but you know you have to keep going.
"There are a few rowers throughout the teams.
"The attributes that make a good rower probably make a good grinder - strength and endurance, and mentally, it can be pretty tough."
Although niggly injuries can be a problem for grinders because of the repetitiveness of their trade, McAsey isn't planning on relinquishing the handles yet.
"Look at 'Meat' [former Team New Zealand grinder Andrew Taylor now sailing with Luna Rossa] - he is still going strong.
"I probably have another two [cups] in me at least. I love it, I'll do it as long as I can get a job."
