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• Interactive Exercise Gaming System Using Center of Pressure - The following explanatory note was provided by authors Aimee L Betker, Ankur Desai, Cristabel Nett, Naaz Kapadia, and Tony Szturm:

  The video game software interfaces with a flexible pressure mat (FSA Shear Force Measurement System*) from which it acquires the center of pressure (COP) signal. The pressure mat has dimensions of 53 cm × 53 cm × 0.036 cm and contained a 16 × 16 grid of piezo-resistive sensors spaced 2.8575 cm apart.

  The mat can be placed on top of different compliant surfaces in order to grade the balance requirements as appropriate. In this case, we used a blue Swiss disc, which allows different levels of air pressure.

  While the game is being played, the instantaneous physical COP x-y position is mapped (slaved) to an onscreen game sprite. Thus, the computer game is controlled by motion of the COP position in a manner similar to movement of the computer mouse.

  In the Apple Drop game, the COP position is slaved to a basket to catch apples dropping vertically from random locations. This is a single-axis game; COP motion is left-right to match the onscreen horizontal motion of the basket.

  In the Dart Game, the COP position is slaved to a vertically moving dart board. This also is a single-axis game; COP motion is forwards-backwards to match the onscreen vertical motion of the dart board.

  Balloon Burst is a 2-dimensional game and more difficult. Target balloons appear randomly on the screen, and the client is instructed to move the small black sprite (slaved to COP position) to intercept the balloon to burst it. This requires body movements in all directions—a combination of left-right and forwards-backwards directions.

  Game parameters can be changed to modify the degree of difficulty and make it easier to score points. For example:

  1. Size of the sprite (basket or dart board) can be increased to reduce precision of the movement.
     
  2. Speed of the apple drops and dart can be adjusted from slow to fast to give more or less time to catch the game objects. Thus, slow and sustained movements or fast ballistic movements are required.
     
  3. In the Balloon Burst game, the size of the balloons can be fully adjusted and the time period given to burst the balloon can be adjusted from 1 second to 10 seconds.
     
  4. The physical mapping of the magnitude of COP position to move the sprite 100 pixels on computer monitor can be fully adjusted so that a small COP motion (eg, 0.5 mm) can move the game sprite, for example, one quarter of the full screen dimension; or, this can be set to 2 cm, as appropriate.
     
  5. The COP position signal can be filtered at different levels to reduce jerky movements and unsteadiness.
     
  6. The number of apple drops, darts, or balloons can be fully adjusted so that the time interval can be varied from, for example, 20 seconds to 2 to 4 minutes.

  Also, note that the people are sitting on electrical beds that can be raised to lift their feet off the floor surface.

  * Vista Medical Inc, 3-55 Henlow Bay, Winnipeg, Manitoba, Canada R3Y 1G4.

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