Mark Geoghegan has punished his body in nearly 70 triathlons covering thousands of miles over the past seven years. He has pushed his fitness to the brink as he swam, biked and ran his way through some of the most grueling races on the planet.

And the 45-year-old has the Tinman to blame for it all. The triathlon, which will celebrate its 29th year Sunday, passes Geoghegan's house in East Honolulu.

The 800-meter swim, 40-kilometer bike race and 10-kilometer run first hooked the Australian transplant to the three-part competitions in 2002.

Though he had grown up a runner and had competed in several marathons as a younger man, he first tried his hand at triathlons when he moved to Oahu. The 2002 Tinman was essentially his first significant foray into the sport and, despite finishing 63rd, the self-employed structural engineer found a new obsession.

“;The Tinman was the triathlon that got me basically addicted,”; Geoghegan said. “;I can see myself at 65 and 75 still doing this. It certainly holds a lot of sentimental feelings that it was the first one that got me into this.”;

“;This”; has included an October in 2005 when he competed in the Honolulu ITU Triathlon World Championships, Ironman Triathlon World Championship and Nissan Xterra World Championship in back-to-back-to-back weekends in Hawaii.

“;This”; has included five Ironman competitions — totaling 12 miles swimming, 560 miles biking and 131 miles running — on the Big Island.

“;This”; has included three top-8 finishes in the last four Tinman triathlons, including a second-place finish in 2007 and a third-place finish in 2008.

Geoghegan has passed on his passion for triathlons to his four daughters. They have all participated in mini triathlons, and the youngest even rode a bike with training wheels in her first triathlon.

Despite his rabid obsession with triathlons — on average, he competes in nine a year, although he completed 15 in one year — Geoghegan is still working on perfecting all three disciplines of the sport.

He readily admits that his swimming is by far his worst leg of the three. It is the most technical aspect of the triathlon, he said, and his swimming technique is far from ideal. Since the triathlons start with swimming, the Australian typically has to work his way from the back of the pack.

His cycling has improved (he once finished the last five miles of the Tinman bike ride on a flat tire).

His strength is running, especially after a long bike ride, and his experience as a marathoner means he makes up most of the ground on the final leg of a triathlon.

“;I'm not a great swimmer, not a great biker, not a great runner,”; Geoghegan said. “;But when you put it all together, I'm a pretty good triathloner. That's the great thing about the triathlon.”;

Geoghegan calls himself a “;weekend warrior”; and trains about 16 hours a week, although he increases that to about 25 hours a week in preparation for the Ironman.

Timothy Marr has won the Tinman the last two years and bested Geoghegan by more than five minutes both times. Geoghegan, who is now one of the older elite competitors in the field, knows that all those miles and his older age may keep him winning his favorite triathlon.

But don't count the 45-year-old out just yet.

“;I'm on the other side where my speed is starting to taper off,”; Geoghegan said. “;But I can still have a lot of fun out there and try to beat some of the guys that are 10 or 12 years younger than me.”;