TRIATHLON : Pumped for Pain : A half-mile ocean swim, an 18-mile bike ride and four-mile run--you won’t be an Ironman, but maybe a Tin man.

So you’re sprawled on the couch, flipping through the channels and the screen fills with bronzed, muscle-packed gods competing in the Hawaii Ironman Triathlon.

You know these guys are totally nuts. They warm up with a 2.4-mile swim, then jump on their bikes for a quick 112-mile ride. For kicks, they top the whole thing off by running a marathon, another 26.2 miles.

You feel wiped out just watching them. But when the music begins to soar, you secretly admit you’re envious of their stamina, their dedication, their powerful legs. Suddenly, you’re inspired to power-through your own strict regimen. Using the strongest muscle in your body, you hoist yourself upright and shuffle over to the fridge for another round of 12-ounce curls.

It’s years before you consider again what it’d be like to swim, bike and run to exhaustion. At a party, your blond girlfriend points out a strapping fellow who competes as a triathlete. “He’s got the most gorgeous legs,” she confides, dreamily.

So what’s wrong with your legs? They reach the ground, don’t they? But she has trotted off to flirt with the hunk, who just happens to be wearing shorts. At night. In the middle of winter.

Sometime that evening, after chatting with the triathlete and stealing glimpses of his rippling quadriceps, you start thinking that someday you might try it.

As fate would have it, someday comes sooner than you expect.

You had noticed an alarming trend with age: Your waistline seems to be keeping pace with the years. Every birthday is greeted by another inch. So you join the YMCA to get back in shape and you just happen to see a flyer about a triathlon.

It’s in Ventura and about three months away. With visions of quadriceps dancing in your head, you decide to go for it.

With great relief, you realize that it’s no Ironman contest. It’s only a half-mile ocean swim, an 18-mile bike ride and four-mile run. But, hey, you have to start somewhere. You won’t be an Ironman, but maybe a tin man.

You buy a pair of running shoes and set out for advice on how to coax your squishy bulk into a hard body. Michael Epstein, the triathlon’s director, sends you to Fleet Feet sports shop in Ventura, one of the event’s sponsors. There, shop owner Rob Fukutomi, a longtime competitor, dishes out wisdom on how to become a triathlete.

“So what sport are you coming from?” Fukutomi asks, in deadly seriousness. “A cyclist?” No. “A swimmer?” No. “A runner?” No. He looks at you quizzically. “Why do you want to do this?”

The last thing you want to do is get into describing another guy’s hulking thighs, so you mutter something about how you thought it would be fun. He seems satisfied.

“Once you do it, you’ll get hooked,” Fukutomi says. “You may not want to do another one right away, but within a couple of weeks, you’ll be thinking about how to improve your time. You’ll say, if I only spent a little more time (training) on the bike.”

Over the next few weeks, you visit the shop repeatedly. You learn about weekly training mileage that should add up to three times the swim, bike and run distances in the race. Say what ?

Jogging is boring but you’re confident you can go the distance. All you want to do is finish the course, after all.

But that attitude soon gives way to sheer panic--after you decide to run a little 10K race at Port Hueneme to size up the local competition.

You sprint out of the start with the fast runners and then settle into a comfortable pace. Pretty soon, guys toting huge guts are passing you. So are grandmothers with jiggling flesh on their arms, mothers pushing baby strollers and a man with one leg.

Clearly, your turtle-trot isn’t going to cut it. You’ve got a new goal, born of embarrassment: You want to finish, and you don’t want to finish last.

In training, jogging, that boring chore, becomes chest-heaving torture, as you embark on a painful effort to reduce your minutes per mile. Some wags say it’s a chance to hear your body talk. Usually yours is screaming, about a side stitch, sore shins or some other kind of gut-wrenching pain.

Bicycling becomes a daily experiment in pain tolerance. Just how much muscle-searing fatigue can you take and keep on pumping? There’s no time to coast on a triathlon, only pedal.

Swimming is no longer a frolic in a heated pool. The ocean is cold and it has no railing to hang onto when you get tired. It also has a wicked streak, taking great pleasure in aiming little waves at your mouth every time you try to breathe.

You begin to learn that all triathletes are obsessed with endurance and speed. They can think of nothing but shaving seconds off their race time.

Sports companies have cashed in by developing a whole line of gear.

So, you buy a popular Speedo-type bathing suit with bike-shorts style padding in the crotch. It’s affectionately called a diaper. The store clerk tells you that if you have to go--you know, No. 1--on the long bike ride, don’t bother to stop.

A wet diaper gets a little droopy on the run, he says, but nobody pays attention anymore.

You buy a pair of lace locks because triathletes, emerging from the cold ocean, struggle tying their shoelaces before setting off on the bike and run. Their little fingers are too cold to work.

You also cart home a batch of strange brews for carbo-loading and replenishing nutrients to fatigued muscles. You notice the high-tech drinks come from a laboratory that makes baby formulas.

You get your purchases home and you begin to think you’ve regressed to an infantile state.

Then you learn that some triathletes exert such an effort that they vomit immediately upon crossing the finish line. Don’t babies do that a lot too?

To your horror, you learn that such convulsions usually draw a small crowd of sensitive, finger-pointing onlookers who otherwise would be at a stock car race hoping to see someone crash and burn.

So race day comes and you think you’re ready. You’ve got your diaper, your lace locks, your green-colored infant formula. You pray you can finish without spitting up.

You set up your gear in the transition area, trying not to be distracted by 600 men and women straight out of central casting for He-Man and She-Ra.

Tugging on your wet suit, you head down to the starting gate that opens to the Pacific Ocean.

Mixing with the triathletes in matching bathing caps, you’re overcome with excitement and trepidation, like a trembling dog, not sure whether to yelp, bolt, or just piddle on the spot.

The starting horn blares and you dash into the surf. You find yourself in a churning school of wet-suited bodies. The ocean roils with swimmers bunched in packs, arms flailing, kicking, clawing their way over each other into the lead.

Before you know it, the ocean spits you out in the beach. Gulping for air, you rip off your wet suit and try to sprint to the transition area. You dunk your sandy feet in a pan of water, cinch up your lace locks and you’re on the bike in a flash.

For the next 57 minutes, you pump your legs as fast as they’ll go. Guys fly past, powered by thighs massive as tree trunks. So do gals in high-cut bathing suits, and that damned grandmother in a sleek racing helmet.

During the last few miles, you’d give up your firstborn for a chance to get off the damned bike--anything to end the pain.

Finally, you arrive. You rack your bike and everything is set for the run--everything but your legs. Your thighs feel like Jell-O; your calves are in knots. You start off at a brisk hobble. It takes a whole mile before your gimp goes away and you rejoin the pace of the others.

Few people pass you now and approaching the finish line you look back and notice, with some meek satisfaction, that there is at least one runner behind you.

You sprint through the chute to scattered applause and stop to catch your breath. Within minutes, you find yourself on your knees, thanking God that at least you didn’t puke.

That night, after a few beers, you tell your girlfriend that it really wasn’t so tough. Sure, you got killed on the bike ride, but you held your own during the swim, and didn’t lose much ground on the run.

You look in the mirror, and you notice that your legs look pumped. But they have yet to transform into a rippling mass of muscle like the Incredible Hulk.

Maybe, if you spent a little more time on the bike. . . .

* THE PREMISE

There are plenty of things you have never tried. Fun things, dangerous things, character building things. The Reluctant Novice tries them for you and reports the results. After all, the Novice gets paid to do them--and has no choice in the matter. If you want to tell the Novice where to go, please call us at 658-5547. If we use your idea, we’ll send you a present.

This week’s Reluctant Novice is staff writer Kenneth R. Weiss, a Times assistant city editor, who finished in 301st place out of 375 men. He completed the course in 1 hour, 47 minutes and 22 seconds.