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geometric Diameter

**The Geometric diameter - a factor stiffening the thoracic cavity - increased prestress**

If well designed, the application of forces to a tensegrity structure will deform it into a slightly different shape in a way that supports the applied forces. Knowing the action of global tension-compression vectors within the thorax cavity, makes it much easier to restore sagittal balance. The thoracic cavity is defined by a CTR unit circle with the diameter of two units, reaching from T1 to T10, with origin at T5. A change in C7-T5 mobility proportions will influence the y- and x-axis, respectively. The circle will change and become elliptical.

**Diameters - Tension type**

Dorso-ventral = x-axis shorter

Cranio- caudal = y-axis longer

Elliptical along y-axis

**Negative Poisson's ratio**

Our analysis of relationship between mobility and structure suggests an arrangement within the thoracic cavity, having a negative Poisson's ratio. When loaded, the structures become thicker perpendicular to the applied force. Such arrangement is expected to have mechanical properties such as high energy absorption and resistance. In this case securing blood circulation through the aortic arc.