In an embodiment, a media playback device is disclosed comprising a first interface configured to communicate with a media output device, a second interface configured to communicate with a data storage device, and control circuitry. Embodiments are used in exercise and other muscle strengthening devices, and may include an electronic control system for monitoring, recording a user’s progress, and for altering or releasing tension to the cable system based on feedback from the user. Therefore, the throughput of the series of wafer processing performed by the substrate processing unit and the exposure apparatus can be improved, and as a consequence, becomes possible to improve the productivity of the device. A change to a value of a property of the cached copy is received.