Designers believe that the hardware doesn't make the shoe heavier than a runner would like because it allows them to cut down on the foam used to shape the shoe bottom.
The running shoe's embedded motor is powered by a tiny Sanyo battery about the size of a watch battery. Developers originally plucked motors from for their early designs.
The computer chip inside the running shoe gauges how a runner's foot is hitting the ground and "tells" the motor if more or less cushioning is needed. The motor attaches with a wire to a plate in the heel. With more tension, the heel becomes more firm. With less tension, the heel becomes softer. A data storage device was attached during testing.
The Adidas_1 was in development for nearly three years. Eight designers worked on the project in secret, even baking their own circuit boards in a toaster oven so people outside the group wouldn't know what they were working on.
Data from hundreds of hours of testing on the shoe was fed into computers so designers could decide how much tension was required on the wire between its motor and heel plate.