The decathlon has always been an Olympic glamour event. The winner is hailed as the ““world’s greatest athlete.’’ America’s past champions were worthy of that description. Track and field was simply something they did, along with hitting a baseball and tossing a football. They didn’t train for the decathlon; they took it on. Those who met the ultimate challenge and triumphed – Jim Thorpe, Bob Mathias, Rafer Johnson, Bill Toomey, Bruce Jenner – became legends. ““The history of the decathlon is so strong because it comes closest to catching the essence of the ancient Greek games,’’ says O’Brien, world-record holder and three-time world champion.

O’Brien’s sculpted body may approach the Greek ideal. But his life as a decathlete bears scant resemblance to the ancients and indeed has little in common with the American greats of yesteryear. He is the best of a new breed of full-time, professional decathletes who, thanks to corporate backing, can dedicate their lives to the mastery of the running, jumping and throwing skills that make up the 10-event competition. Each day O’Brien lifts weights. Mondays, Wednesdays and Fridays he devotes to running, long jump, high jump and shot put. On Tuesdays and Thursdays, Dan practices the discus, pole vault, javelin and hurdles. ““This is a full-time job,’’ says O’Brien, who will turn 30 the day before the Atlanta Games open. ““I go out each morning and don’t get home till 6:30 at night – and that’s only if I don’t take a massage.''

O’Brien and other elite American decathletes are transforming what once was art into craft. O’Brien is blessed with speed – and, more important, explosive speed. That’s critical in the decathlon where eight of the 10 events take less than 15 seconds to perform. But in his early competitive years, he depended on his natural talent too much. Now he strives to repeat each skill so many times a week that the techniques are second nature to him. ““You don’t want to be thinking,’’ says O’Brien. ““What you want is to have done all these things so often that if you can just get your mind out of the way, your body will do it naturally.''

He learned that lesson the hard way. In 1992 O’Brien was also the gold-medal favorite. And thanks to Reebok’s relentless ““Dan and Dave’’ ad campaign, he was already a household name. But at the Olympic trials, he failed to clear a single height in the pole vault and didn’t even make the American team. An inexperienced pole vaulter, Dan missed twice. With one attempt left, panic began to seize him. He hadn’t vaulted enough to rely on technique. So he floated helplessly under the bar. His coach, Mike Keller, realized there would be no escaping the burden of that flop. ““If we didn’t think about it, others would make us,’’ says Keller. ““So instead we thought about it a lot.''

He and O’Brien’s other coach, Rick Sloan, would ““play a lot of games with Dan.’’ They created hypothetical situations, many of them centering around a do-or-die last chance in the pole vault. The work paid off. At this year’s trials it was O’Brien’s effort in the pole vault, the eighth event of the two-day competition, that propelled him into first place. ““I’ve learned,’’ he said, ““that you can’t rely on your good events and be afraid of the bad ones.''

Not all O’Brien’s mental preparation has centered around the pole vault. The decathlon requires extraordinary mental discipline. The athlete must peak physically and emotionally for 10 separate events, but then essentially shut down, not wasting any energy. O’Brien learned not to overreact to his results in individual events. ““If you start out with a strong 100, you can’t sit there and feel great about it,’’ says Keller. ““And if it’s a lousy one, you can’t feel crummy. Each of his great decathlons has been achieved a different way.’’ O’Brien won his third world title in Sweden last summer without finishing first in any of the 10 events. By finishing consistently high in each of them, he accumulated more points than any of his rivals.

O’Brien has remained in Moscow, Idaho, where he competed for Keller at the University of Idaho. Sloan, a 1968 Olympic decathlete, coaches at nearby Washington State. While this team has proved formidable, the Northwest locale has seldom been ideal. This year’s wet and cold spring made it difficult for O’Brien to get in all his conditioning work. At the trials in Atlanta, he was ahead of world-record pace through nine events. In the brutal heat, Dan was relying on IVs for hydration.So he played it safe and finished the 1,500 at a snail’s pace to secure his title and, more important, an Olympic berth. If he finds himself in the same position at the Games, Dan says he’ll go for gold and the record. ““The decathlon,’’ he says, ““is a matter of heart.’’ He’s waited four hard years to prove that the world’s best body is driven by the world’s bravest heart.