An apparatus for recording and reproducing digital information uses a disk recording medium in which data recording area is divided into plural zones in the radial direction, and defect information is managed for each zone. The yoke may include a bearing surface that provides a low coefficient of friction, allowing for a greater biasing force against the rack shaft. The sapphire substrate may comprise bulk sapphire or may be a conventional substrate material with an uppermost sapphire layer. The machine provides a monitor to enable the athlete to track the progress of the exercise, and to determine whether the exercise is being performed correctly. The systems and methods can then adjust the price of the item for sale on an automated, or even semi-automated, basis without the need for manual intervention.