*2.2. Experimental Protocol*

An experimental campaign has been designed and performed to extract the UCOP coordinates while asking the volunteers seated on the chair to undergo a task sequence with increasing levels of cognitive engagemen<sup>t</sup> defined through a dedicated test (i.e., Stroop test).

The Stroop test has been successfully employed for driving volunteers from a natural and relaxed position on the seat of a chair to different ones associated with a stressing condition while increasing the difficulty level of the performed task. Details of the designed Stroop test are given in the following.
