I PREFER to obsess about chocolate chip cookies rather than workouts, which is why I'll probably be a terrible triathlete. My friend Eric, an avid triathlete, wears a stopwatch when he swims to know exactly how long his workouts are. He even stops the watch between sets to make sure he's not "cheating" by including rest time. At the end of the day, which also includes an early morning bike or run, he fastidiously enters his workout time, distance and speed into triathlon software. Eric can have long conversations about how yesterday's workout compared to workouts six months ago, or even a year ago.

The Hawaiian Ironman, the Everest of Triathlons, made the sport famous when it was first covered by CBS in 1982. Even though most races fall far short of Ironman length, which includes a brutal 2.4-mile swim, 112-mile bike and 26.2-mile full marathon run, to successfully complete any triathlon takes concerted training and at least a modicum of obsession. Girding myself for six months of pain, I'm training for the Washington-area triathlon season, which begins in late spring.

"It's real important to maintain your family and your job, because [triathlons] can become compulsive in nature," explains Kim McLaughlin, 34, of Reston, who placed second in her age group at the USA Triathlon National Championship this year. She should know, at the peak of her training McLaughlin's workouts include an hour swim, a three- to four-hour bike and finally a 30- to 60-minute run. McLaughlin frequently reminds herself that her husband and two children, ages 2 and 3, come first. "I've seen so many marriages crumble and people just get so overtaken by the sport because it requires a lot of time," she says.

My wife seems worryingly at ease with my workout schedule. But then, when I go for a jog, I'm not gone for long. I ran a mile my first day out and it took me 11 minutes. You could walk briskly and keep pace with me.

How much time you need to train for your first triathlon depends on your fitness level and athletic background. Baltimore-based triathlon coach Troy Jacobson says that people with a competitive athletic background can be ready for the shortest triathlon, a "sprint" triathlon (0.75-kilometer swim, 22-kilometer bike, 5-kilometer run), in just two months. The rest of us need a little longer to prepare. "If it's someone who is a 35-year-old person who has been inactive for 15 years, I'd say give yourself at least half a year of steady training before doing it," Jacobson says.

Triathlons, though, are not limited to the young. At the Triathlon National Championship, in St. Joseph, Mo., in September, three men in the 75- to 79-year-old age group finished the race. Fifty-five-year-old triathlete Dodie Gill of Reston started doing triathlons five years ago and this year placed 10th in her age group at the National Championship. When Gill began jogging she could run only a few hundred yards at a time. Now, she often does 13 different workouts a week, regularly getting up at 5 a.m. to run before work, taking spinning classes to strengthen her biking muscles and swimming with a masters team four times a week. Her biggest concern is staying injury free. "I don't feel 55 inside, but my joints are [55] so I have to take care of them," she says.

Jacobson gives two important pieces of advice to beginning triathletes. First, consistency is more important than long hours. That is, it's better to ride your bike six days a week for one hour than to take one extra long ride on the weekends. "If you're just getting out there and doing a sport and then waiting three or four days before you do it again," you're exercising, but not training for a triathlon.

Second, concentrate on your weaknesses. Bad as I am at running, I'm a worse biker. Zero-body-fat Sharon, the spinning teacher at my gym, eyed my spindly legs when I walked timidly into class. "First time?" she asked, and then turned off the lights, cranked George Michael and barked at us for 45 minutes while we madly pedaled our stationary bikes. "Up off your seat!" We stood up on our bikes as if ascending a steep hill. I followed her directions as best I could. Sprint! Stand up! Sit down! Keep sprinting! Stand up again! Ears ringing and legs like jelly, I could barely walk out the door at the end of class.

Swimming is usually the weak event for most beginning triathletes. According to Jacobson, new swimmers are "like rocks in the water," because their form is so bad. To rectify this, poor swimmers should join a local masters swim program. The programs provide structured workouts, a social atmosphere (swimming can be deadly dull) and, most importantly, tips on swimming technique.

But fear is also a factor for the beginning swimmer. Triathlon swims are in open water, in a lake or the ocean, amongst hundreds of thrashing competitors. "Swimming can be very scary, because you have these mass starts and you can get kicked in the face, head, all over the place," Gill says. At the National Championship, she let the bulk of competitors go first to avoid the mayhem in the water. She also finds that a wet suit's buoyancy and warmth add to her confidence during the swimming portion. If the race allows it, Jacobson recommends wet suits for all of his competitors.

Gill and McLaughlin have both qualified in their age groups for the US Triathlon Team, which will compete in the World Triathlon Championship in Perth, Australia, in April 2000. Although Gill is a competitive, endorphin-rush junkie, she says it is the camaraderie that has kept her going. "It is the most nurturing, wonderful environment. . . . Everyone knows they're a little crazy to be doing this, and so we all kind of like each other."

While Gill shoots to win half-way across the world, back in D.C., I aim to finish.