Bill Curcio had run six Ironman Triathlon qualifiers around the U.S. when he decided this year to take the challenge one step further.

Curcio, a New Canaan personal trainer, intensely trained and dieted for a year to prepare for the Ironman Cozumel in Mexico, one of almost 200 races internationally that qualify a small number of athletes for the ultimate test: the Ironman World Championship in Kailua-Kona, Hawaii.

The Nov. 30 race was more difficult than his previous competitions, and one of Curcio's most challenging experiences.

"It was extremely hard, probably the hardest thing I've ever done in my life," the 41-year-old said.

Ironman Triathlon is a series of long-distance races organized by the World Triathlon Corp. and is considered one of the most difficult sporting competitions in the world. Each race includes a 2.4-mile swim, a 112-mile bicycle ride and a 26.2-mile marathon run. Most qualifiers take place in that order, starting at 7 a.m., and have a 17-hour time limit -- with no break.

Ironman Cozumel offers 40 qualifying slots for the world championship. Surrounded by the Caribbean Sea, the island is 10 miles off the eastern coast of Mexico's Yucatan Peninsula. Despite the paradise-like setting, however, Curcio saw many athletes abandon the grueling 140.6-mile course before the end.

"It was hot, 88 degrees, " he said. "I wasn't used to that because I was training here (in the U.S.). The wind was about 30 mph. It kept picking up and then it was blowing all over the place. It was never helping you. It was always pushing you to the sides."

At one point during the race, Curcio felt as if he "was falling apart." He lay down on the road for about 20 minutes and thought about quitting.

That's when the name of the race begins to make sense. The same way Marvel's superhero Tony Stark controls much of his "Ironman" armor with his mind, aspiring and professional triathletes can control their bodies with their minds. At least that's what Curcio did.

The Greenwich native said he thought about how much he had trained for that race, how much he wanted to finish and what the accomplishment would mean to him. He then stood up and went on to finish the race in 14 hours and 24 minutes, which ranked him 47th in his age group -- 40 to 44 years old.

"It's such a pressure that it kind of humbles me, " he said. "I like having that goal. When you set your mind to it, you can accomplish pretty much anything."

To cross the finish line, Curcio said, is likely one of the best feelings one could have.

"I wish I could give people that feeling because at some points you don't know if you're going to make it, " he said. "People are dropping out, you're helping people on the way. And you think, `You can finish this thing that you've been training for a year and it's over.' "

Although he didn't qualify for the world championship, the founder of Curcio Training said every mile of Cozumel was worth it.

"It's beautiful, " he said. "The water is so clear. It was the most beautiful swim. The water is almost soothing. ... It was a life-changing experience to me."

Michael Weiss, of Austria, won the race for the second consecutive time this year with time of eight hours and 12 minutes.

Curcio's advice to people is to set high goals for themselves. His race partner, for instance, is a 61-year-old friend.

To prepare for the race, participants have to train seven days a week for six months to a year. The training includes a high-calorie and carbohydrate-rich diet. During the latest race, Curcio burned 9,000 calories even though he consumed several packets of energy gels as well as Gatorade.

Curcio, who has finished five of the seven Ironman qualifiers he's run, has no plans to quit the races. After running Ironman qualifiers in Wisconsin, Maryland, Kentucky, Florida, Ohio and Mexico, Curcio said he will go back to Maryland -- where he ran his first Ironman in 2005 -- next summer.

His goal remains to qualify for Hawaii.