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Postural Strategies and Sensory Integration: No Turning Point between Childhood and Adolescence

Figure 3

Left upper panel: Diagram of the shoulder roll angle with respect to the external axis, θ_a, and with respect to the supporting platform, θ_r.

With x: lateral axis, y sagittal axis and z vertical axis. Right panel: angular roll displacement of the supporting platform (upper trace), the absolute angular displacement of the shoulders (middle trace) and the relative angular movement of the shoulders with respect to the supporting calculated every 8.33 ms during a trial using the formula: with , the angular orientation of the shoulders relative to the support, and and are the absolute shoulders and support angular orientations,s respectively. (Lower trace). Left lower panel: Diagram of the absolute (Sd Abs) and relative (Sd Rel) roll dispersions of the shoulders, according to the definition of the anchoring index (AI). Formula of the AI = (Sd Rel²−Sd Abs²)/(Sd Rel²+Sd Abs²) where Sd Abs is the standard deviation of the angular distribution about the roll of the segment under investigation with respect to the absolute allocentric reference (absolute vertical direction) value and Sd Rel is the corresponding standard deviation of the angular distribution with respect to the moving platform. In this example, AI is positive, which means that the shoulders are stabilized in space independently of platform movements.

doi: https://doi.org/10.1371/journal.pone.0013078.g003