You can feel it through fabric. The thicker the fabric the less of a shock. We have tested with; light dress pants = good shock, jeans = feels like a pinch. Something to keep in mind, if you put fabric on the chair then it will have to go through that and then the person's clothing.
WARNING: HYDRAULIC AND PNEUMATIC POWER SYSTEMS CAN FAIL THROUGH MISUSE, AGE OR MALFUNCTION. THE SYSTEM DESIGNER
IS WARNED TO CONSIDER THE FAILURE MODES OF ALL COMPONENTS USED IN THE DESIGN AND ENGINEERING OF ALL SYSTEMS AND TO PROVIDE ADEQUATE
SAFEGUARDS TO PREVENT PERSONAL INJURY OR DAMAGE TO EQUIPMENT IN THE EVENT OF SUCH FAILURES