You don't often find scientists staging arm-wrestling tournaments &emdash; let alone competing in them. But the match scheduled tomorrow at the International Society for Optical Engineering conference in San Diego is no ordinary bout.

For the first time, researchers plan to pit man-made muscle against living tissue &emdash; in this case the sinewy limb of a San Diego high-school senior. The purpose: to spur scientific interest in a little-known but promising class of plastics that expand and contract when jolted by an electrical charge.

Officially known as electroactive polymers, the material more frequently is referred to by its nickname: artificial muscle.

Long regarded as a laboratory curiosity, the material has begun attracting more-serious attention. Researchers are incorporating it in plans for everything from toys and robots to implants and prosthetics. Some scientists envision a day when the material might replace real muscle in people whose own fibers have failed.

"The properties of artificial muscle are getting much closer to that of biological muscle," said Selahattin Ozcelik, a Texas A&M University robotics researcher.

Theoretically, Ozcelik said, artificial muscle can be used in place of any mechanical motor and offers several key advantages. Lighter than a traditional motor, artificial muscle can unleash quick bursts of stored energy. As a plastic, it's also capable of bending and twisting.

Financed by a small grant from the Office of Naval Research, Ozcelik and his colleagues have designed a snakelike robot composed entirely of braided artificial muscle fibers.

By electrically stimulating the fibers in the right sequence, Ozcelik said, the robot could slither into tight spaces or over rough terrain in ways that a mechanical robot would find hard to match.