The Karate Kid learns a new martial art in "Vision Quest," a tale of rasslin' and rites of passage based on the novel by Terry Davis. It's the usual dumb stuff -- he strives, he fails, he falls in love, he strives some more, he wins. You need strong hands and a heavy set of nutcrackers to break this tedious shell, but inside there are some surprisingly sharp insights into male teen-age psychology and a marvelous performance by Matthew Modine.

When Louden Swain (Modine), a high school wrestler, turns 18, he decides "this is the year I make my mark." A statewide contender the year before in the 190-pound weight class, he decides to drop 22 pounds and confront the league's reigning menace, a tough hombre named Shute (a terrifying Frank Jasper). Running in a rubber suit, skipping rope like a human gyroscope, drinking ice water while lesser men gorge on burgers and ribs, Louden approaches his showdown with a loony single-mindedness. Add to this a new obsession -- Carla (Linda Fiorentino), a tough-talking Jersey moll whom Louden and his father (played by Ronny Cox with pleasant integrity) take into their home.

"You're on a vision quest, man," says his chum, Kuch (amiable Michael Schoeffling), drawing on American Indian mysticism. "You're trying to find your place in the circle." The filmmakers, director Harold Becker and talented screenwriter Daryl Ponicsan ("The Last Detail"), never make it clear how you're supposed to take this. As a serious theme, it's hooey, but as characterization, it fits -- kids about to launch on their own are prone to this kind of fudgy mysticism. That's the problem with all of "Vision Quest" -- when the movie ends with Louden narrating off-screen his "live for today" philosophy, it's plausible in his mouth, a joke for adults.

Tossing about his lank hair and the flap of his shirt tail, his face split by a goofy grin that stretches to the ends of the screen, Modine has a gangly, charming presence. His Louden seems to be seeing life for the first time -- not just wet behind the ears, but soaking wet. Louden observes everything, including his own body, with a genial, clinical detachment; a biology major who wants to be an astronaut/physician, he explains his own fainting spells as intriguing phenomena, the result of "a temporary nitrogen imbalance" and fluctuating sodium levels, as if he'd read about it happening to someone else. And when he throws himself into wrestling, it's only a logical response to his discovery that he has "perfect balance" and "kinesthetic sense." Connect A to B.

Modine rattles off words in a torrent -- everything that happens to Louden is interesting to him, worthy of comment, and he's so inside his own head that he assumes it's interesting to everyone else, too. When Carla heckles him -- "Who the hell are you?" -- he answers blithely, "I'm Louden Swain." It's a laugh line, but it also shows him trying his identity on for size.

Louden's psychology informs their love affair, lending it an unusual complexity. Like everyone else in this kind of movie, Louden just doesn't want to be a virgin anymore; but it also plugs into his competitiveness -- he doesn't want to fail at sex, or anything else. Besides, in the way teen-agers have of glorifying their most basic and banal urges, he genuinely feels he's in love. And as someone whose life is dedicated to rolling around half naked with other guys, he's worried that he's gay -- when a male guest in the hotel where he works propositions him, he rebuffs him, but he's turned on, too (another new experience!).

The romance itself, though, is humdrum -- Fiorentino delivers all her lines in the same pseudo-Bacall, deadpan basso, so they tend to come out hooters (as in "I bet your grandfather was a real animal when he was young"). Worst of all, the "Rocky" elements are badly managed. Shute looks like he could neatly fold a half-dollar between thumb and forefinger -- he dwarfs the slight Modine. So how does Louden beat him? Simple! The music swells and the camera goes into slow-motion. Wrestling coaches, take note.

Vision Quest, opening today at area theaters, is rated R, and contains some profanity and sexual themes.