This abstract presents a computational model and a software library for the EyesWeb XMI platform to measure a mid-level movement quality of particular importance to convey expressivity: Postural Tension. A whole body posture can be described by a vector containing the angles between the adjacent lines identifying feet (the line connecting the barycentre of each foot), knees, hip, trunk, shoulders, head, and gaze (eyes direction). Postural Tension is the extent at which a movement exhibits rotation of these multiple horizontal planes including spirals. The abstract presents a definition of this mid-level quality, and describe a demonstration: movement of a user is captured with a low-cost wearable device, postural tension and transmission of energy through the body are then extracted, visualized and sonified.