A very important component in analyzing movement is the concept of simultaneous movement. The movement possibilities of a single skeletal limb segment are limited and due to the fixed bone length, the points in reach of the limb always form a sphere. The possible movement paths may be well defined by a concise set of instructions and parameters.
As opposed to that the resulting spatial paths of several limbs moving in concert are highly complex and it is impossible to describe this complexity directly with a limited set of instructions.
- a simple arm movement.
- Then a tilt of the pelvis is simultaneously performed with the arm movement, and the coordinate system of the arm is tilted with the pelvis.
- And now we can see the arm movement with the pelvis once more, but this time the path of the arms remains fixated according to the spatial coordinate system.
The following example will show the last two variations once more: This time the arms’ spatial trace is drawn with a colored curve.
- The red curve shows the arm path in its body related mode.
- The green curve shows the spatially fixated path.
The distinct movement paths may be clearly noticed. This difference is only caused by the application of a different coordinate system to the arms.
As there are many more movement parameters, which can be modified, there are actually endless possibilities for creating variations on existing spatial paths.
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