Rex Jameson bikes and swims regularly, and plays tennis and skis when time allows. But the 5-foot-11, 180-pound software engineer is lucky if he presses 200 pounds—that is, until he steps into an "exoskeleton" of aluminum and electronics that multiplies his strength and endurance as many as 20 times.

With the outfit's claw-like metal hand extensions, he gripped a weight set's bar at a recent demonstration and knocked off hundreds of repetitions. Once, he did 500