By - Alan Farnham

(FORTUNE Magazine) – Watch Roger Charter, a double amputee, jog down a straightaway atop mechanical legs, and your mind reacts in stages. First, shock: This man, loping along, has metal and plastic where his legs and feet should be. Second, amazement: He moves gracefully, doing what no above-the-knees double amputee has publicly done before -- run step over step. There must be thousands of people who would pay anything to be able to run like this. There are. By one estimate, more than 300,000 Americans are in the market for lower- ( limb prostheses. Feet, being farthest from the heart, suffer more damage from circulatory diseases than do the body's other extremities. As a result the need for lower-limb prostheses is far greater than for upper-limb prostheses. The potential market for replacement feet alone is estimated to be about $20 million a year, and seven U.S. manufacturers are competing for it. Only one, Sequel, is publicly held. Sabolich Prosthetic & Research Center designed the foot Roger Charter has been testing. Like some competing feet, the Sabolich model uses a springy plastic to absorb and store the energy produced after the heel strikes the ground. As the foot moves through its gait this energy is released, helping the foot spring forward. West Germany's privately held Otto Bock leads both the U.S. and international markets with a diverse line of upper-and lower-limb products. Not all its sales, however, come from prostheses. Experimenting years ago with new materials for prosthetics, the company developed special foams that are now used for steering wheels and dashboards in Mercedes-Benz and Volkswagen cars. - A.F.