WHO ARE THEY AND WHY DO THEY DO IT? -these men who dedicate themselves to building bodies like Hellenistic statues; who crisscross the world competing for titles as grandiose yet as publicly uncelebrated (Mr. America, Mr. Universe, Mr. Olympia) as their gargantuan physiques; whose daily lives are as rigidly defined and regulated by their obsession to mold the ideal body as any other master athlete's is towards perfecting his craft. Yet, rather than the public acclaim that normally follows an athletic triumph, only their fellow muscle men know who they are and know the price they have paid to win their incredible bodies. Novelist Charles Gaines and photographer George Butler have spent the last two years trying to capture the essence of this strange, joyful, exotic world: "We have been to quite a few places tracking bodybuilders, seeing contests and putting together the materials here. If we felt at times a little like 19th-century explorers -like Doughty, perhaps, off trekking through Arabia -it was because we found bodybuilding to be as primeval and unmapped as parts of Labrador. Nobody, we discovered, had been back into it to send a report on what it was like. This struck us then as peculiar, and it still does.