Sensitivity of back and buttock
It is difficult to decide on the foam stiffness in different parts of a vehicle seat. Therefore, a study was done to determine differences in sensitivity in areas of the human body contacting the seat pan and backrest. This difference in sensitivity can be used to design a more comfortable seat.
The sensitivity is recorded at 32 points touching the seat pan and backrest (the holes in the seat are the 32 points) at 23 subjects by pushing a cylinder with a diameter of 20 mm until the participant reports that it is not comfortable anymore. The force at which this is reported is recorded with an advanced force gauge.
The area of the human body having contact with the front of the seat pan is more sensitive than the rest of the body touching the seat pan. The area of the seat touching the shoulders is significantly more sensitive than the area in between the shoulders and lower in the back.
Translating this directly into seat design should be done with care. Tests with subjects are still needed to affirm the assumed relationship between sensitivity and foam softness, but also information on the form of the seat and the complete use of a seat needs to be incorporated in the design, like vibration while driving and in- and egress.