There is no more painful anomaly in modern life than the American skiier. He hits the hill with a mega-tech profusion of gear that would make a NASA designer drool: super-tuned Teflon-plated bindings with more releases than Kenny Rogers; carbon-fiber multi-ply skis with auto-firing brakes; power-flex polyurethane boots; and spring-damped poles of rare occult alloys.

And yet this hyphenated bionic phantasm still ends up impaled on trees, squashed into goosedown aspic on a drop-off or pummeled by moguls until he lies there like a bag of Alpo.

The problem is pilot error. And not just the party-time dingbats with a bellyful of tacos and a snootful of wine, all gasifying on top of this morning's hangover. It also can be anyone who, because of inadequate conditioning, debilitating heat loss or bum nutrition, reaches the point of exhaustion where most accidents happen.

As sports go, skiing is not one of your monster chow- burners. According to the President's Council on Physical Fitness and Sports, a 174- pound person expends 110 calories every 10 minutes of vigorous skiing--about the same as squash, but much less than ice hockey (235), walking upstairs (205), water polo (140), listening to James Watt (1,550) or reading the Form 1040 instructions (25,000). Still, it's heavier than Ping-Pong (65), croquet (40) or shooting pool (25). And at five or six hours a day, it can drain your crankcase to the tune of 1,500 calories above normal.

Moreover, the muscles required are specialized, and so is the conditioning. "Running won't do it," says Gabe Mirkin, co-author of The Sportsmedicine Book, since skiing calls for a more even stress ratio between quadriceps and hamstrings. Mirkin advises ice-skating or roller-skating or bicycling, along with the classic prep drills: walking up stairs, sit-ups and "the human chair." (Put your heels 18 inches from a wall and sink into a sitting position until your thighs are parallel to the floor. Hold for 60 seconds or until the quivering starts to loosen your fillings.) Dr. Richard Reff, an orthopedic surgeon, skiier and member of the sports medicine committee of the D.C. Medical Society, adds semi-squats (with the feet straight and heels on the floor, sink half- way down) and this deceptively torturous item: With ski boots on, lift each leg 8 inches off the floor and hold for a count of five.

And spend 10 minutes stretching before you go out. Reff recommends a minimum three-exercise warm-up: 1) Stand on a staircase facing upstairs with your toes on the step and your heels off. Raise your heels up above step level, and then lower them below. 2) Touch your toes with your legs apart. 3) Lie on your back and bring each knee separately up to your chest, then both together.

Once on the mountain, you'll perform and feel best if you keep your gizzard warm. "If the core temperature starts to drop," says Dr. Kenneth Chase, a Washington internist and skiier, "the physical reflex is an intense vaso- constriction in the periphery" --blood crowds to the innards, causing cold hands and feet. And your stamina starts to go. Mirkin says that when body temperature drops one degree, "You begin to shiver and your voice becomes slurred." Most slopesters can function that way, but at 2o F, "get the hell out of the cold. You lose control of your hands." At 4o, "you lose control of the feet," a real inconvenience at 30 m.p.h. Another warning sign, Mirkin says, is a sudden burning or itching sensation, presaging frostbite. When your surface temperature reaches 59o, "the body tries to save the skin." Previously white areas flush with the effusion of blood, producing the itch. Alcohol obscures these warnings: "You can die," Mirkin says, because the booze "inhibits the shiver response" while dilating the vessels on the skin.

The skiwear industry's obsession with jackets, sweaters and snug-hugging fashions has become a vital element in slopeside selective-breeding rituals. But it puts too much insulation on the upper body, not enough on the lower. From the navel up, triple layering is most efficient: An impermeable outer shell over a down vest or other insulator over an inner layer designed to draw potentially chilling moisture away from the skin. "You don't want cotton at all," says Mirkin, "it just holds sweat. The ideal thing is loosely woven wool. It retains its insulation and carries the sweat right through."

So does the new non-absorbent polypropylene underwear--but wear the bottoms only, says Reff. Too much top-torso padding makes Stowe feel like Rangoon, causing a core meltdown, excess sweat and fogged goggles. (If you can't stand the heat, don't get out of the parka; expose a wrist or hand and let your body cool slowly. Or briefly doff the hat: A denuded scalp, with its dense network of blood vessels, is a huge source of heat loss.) For cold feet, remember, "You're not going to be twice as warm by putting on two pairs of socks,' Reff says, since "it may cut off the circulation."

There is no particular grub that will keep you warmest, says Dr. Nathan J. Smith of the University of Washington's sports medicine clinic and author of Food for Sport. In fact, "for the intense gung- ho skier," he says, "the most important thing to watch is fluid loss." Weakness from dehydration can "really contribute to injury." And make them hot liquids, says Chase, who urges a high-carbohydrate diet with minimum fat. The human machine runs on glycogen stored in the liver and muscle tissue; the fatter the fare, the longer it takes for the goo to get there. So hold the fondue--along with the ubiquitous grease-bomb triad of hot dogs, burgers and those alleged french fries that have the texture of tub caulk. Nix, too, on heavily spiced foods (also notorious gut-laggards) and your flatogenic veggies (apples, cabbage, beans, onions et al.) with their bloating consequences.

Finally, tune up your brain. With shorter skis and more reliable bindings, skiing has become consistently safer since the early '70s; traditional leg breaks are few, and the most common injuries are now to the knee (from failure to fall correctly--behind the skis) and to the head and upper body (from pitching forward while skiing too fast). But your rig can't help you if you don't maintain it. Dr. Robert L. Johnson, a ski-injury expert at the University of Vermont, believes that 80 percent of leg and foot injuries are potentially related to equipment problems, and that nearly half of all injuries probably result from binding- release failures. (A recent study found that over 50 percent were set too high.) Have your bindings tested yearly at a reputable shop, check them yourself on the hill by twisting out of your skis and slather the gadgets nightly with silicon. If you take care of your equipment, your equipment will take care of you.