BODY WATCH : Heart Pounders : Want to work up a really good sweat? Think Tae Bo Aerobics, hill running and kick-boxing.

Pardon this fanny for even existing, but I don’t have all day to buff my babeage at the gym. I’ve got more like an hour, max--and in that hour I want the kind of workout you can aim like a can of Raid and, zap! terminate fat cells.

Can you relate?

If not, did you catch the much publicized, though criticized, Harvard study in the Journal of the American Medical Assn. last spring that suggested that only “vigorous” exercise can extend your life? It’s the one where researchers tracked 17,321 men for 26 years and found that those who expended at least 1,500 calories per week on intense workouts had up to a 25% reduced risk of dying compared with others who spent less than 150 calories per week doing mild or moderate exercise.

Weigh the evidence; weigh your flesh. And if, in the balance, you decide you’re one of us hard-core fanatics, here’s where to get the best sweat in town.

(One quick note about using sweat as an indicator of energy expenditure: It’s a crude test at best. After all, you can sweat bucket-seats without lifting a finger--say when you’re stuck on the 405, late for the shrink, calculating how many dollars you’re losing every minute that blacktop doesn’t budge. “It’s very imprecise,” says Russell Pate, professor and chairman of the department of exercise science at the University of South Carolina, explaining that heat and humidity make a big difference in determining how much you perspire. Also, if you’re in a dry climate, the moisture will evaporate from your skin before you ever see it.)

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Smack Attack: Orienteering and cross-country skiing, which top the calorie charts, are just a mite impractical for those of us who live in a city that would be desert. But boxing, which burns a possible 864 calories per hour by some accounts, could be just what the trainer ordered. Make that kick -boxing, and you’ve got a metabolic monster of a workout.

For those of us who prefer to keep the nose we were born with (or the ones we purchased, as the case may be) Bodies in Motion Cross-Training Centers specialize in “no fighting, no biting” boxing and kick-boxing. I pop into the new Santa Monica gym (you can take one class for $10; it’s refunded if you join) where they wrap my hands and escort me to the room with 35 punching bags bolted to the ceiling and floor.

Right now, as we start classes by jumping rope to Brazilian rap music, I don’t see a thing because drops of sweat are dripping into my eyes. After donning red boxing gloves and practicing a series of punching and kicking drills, we each take a bag and have at it. There’s nothing that gets your kishkas schvitzing like smashing into old baggage--physical or emotional, and this can be both. Thump, sweat, breathe, thump.

“Empowering, huh?” smiles the instructor, Fernando Rodrigues, whose grandfather owned a boxing gym in Trinidad. “To learn kick-boxing the traditional way, you’d have to pay your dues, doing the basics over and over. This is a crash course. It’s the ‘90s way, the California way.”

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Going in Circles: For the love of the Lifecycle, why not take a spin on the stationary bike and cube the intensity? That’s what you’ll experience in a 50-minute class called “studio cycling” at Main Street Studio in Santa Monica.

I meet my friend Stephanie Barry there. She’s a woman who will spend her weekend pedaling 500 miles through Death Valley without stopping and stays in shape with this sort of workout.

(Johnny Goldberg, reinventor of this wheel--and the trademark name Spinning--has just opened his Johnny G’s headquarters in Culver City; you can also find Spinning in other clubs as well.)

Following Barry, I hop on one of the several bikes that are set up in a U, and plug my headphones into a wire that dangles from above, attaching me to our instructor like an umbilical cord. The instructor, Joelle Mancuso (who now teaches at Johnny G’s) pedals away in front and takes us on an imaginary journey.

“Getting up this hill is no different than making that phone call you hate,” she says over music from Cirque du Soleil, coaching us to increase the resistance and stand out of the seat for the climb.

At one point, on a speed dash, I look down and see my legs going faster than what I thought was humanly possible--that is, until I notice Barry’s have blended into the blur of the spokes. We’re both sweating like sprinklers.

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Faith Without Work Is Dead: That’s what a banner says at Billy Blanks World Training Center in Sherman Oaks, where a quick scan suggests the amount of body fat walking around the studio could fit into my ballpoint. Blanks, a world karate champion, has blended tae kwon do and boxing into a cardiovascular workout called Tae Bo Aerobics that is definitely not for the weak of lung.

It’s Blanks’ 21-year-old daughter, Shellie, a fourth-degree black belt in tae kwon do, who teaches the class. And she gets right down to business. When the clock strikes 6 p.m., we punch in, literally--jabbing, hooking, knocking the wind out of, well, the air. Within 20 minutes the mirrors are fogged and yesterday’s mascara is flowing in the canyons of my smile lines, which are not in use. We kick and punch until the hour is up, except when we do a few million sit-ups for good measure. “I’ve had more people tell me they have never sweated so much in their life as in my class,” Shellie Blanks says.

And that might be anywhere from one cup to more than three quarts--at least, that’s how much you’d sweat during an hour of moderate exercise, says Robert Murray, director of the Gatorade exercise physiology lab in suburban Chicago. The point, Murray stresses, is not to gloat over the puddles by your Nikes, but to drink the equivalent of the liquids you lose. That way, you’ll be able to exercise longer and harder.

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Can You Top This? One requirement of Teyana Viscarra’s Gravity Training is that you come with a full bottle of water. Preferably two. Does that give you a clue?

I meet her one evening in the hills above the Hollywood Bowl, where she has set up colored cones along a quarter mile of trail--the kind you’d be happy to ski down. If you’re looking for a workout that will reduce you to mop-up material, go no farther.

“Hill choreography,” for example, consists of courses such as: Run up to the yellow cones, turn around and jog backward, farther up to the green ones, skip even higher to the orange, and run back down. Four reps leaves one panting; students typically do 10 to 15.

By the end, I hear the “Star Spangled Banner” playing at the Bowl below, and all I can think about is how they’re going to sit down afterward. I still have one long, last uphill power run to complete. Fortunately, it’s not over the Malibu Sand Dunes where Viscarra sometimes takes her students--after which, as Viscarra puts it, “you feel like King Kong.”

Right now, I feel more like the hamburger meat Kong-boy just ate for lunch. But at least it’s McLean Deluxe . . . as opposed to a Big Mac.