A seat cushion for a chair has a plurality of cushion grooves deformed a seat load of a user formed in a central portion of a lower surface thereof, the plurality of cushion grooves include: a plurality of main cushion grooves disposed in a plurality of rows in a front-rear direction and a left-right direction and spaced an equal interval from each other; and a plurality of sub-cushion grooves each connecting one of the plurality of main cushion grooves and formed in a straight shape with narrower widths and smaller depths than the plurality of main cushion grooves.

An electrically operated multi-functional chair comprises a rotatable chair base, a seat, a backrest, and a leg rest. The rotatable chair base is connected to the underside of the seat; the rotatable chair base allows the seat to rotate. The seat has a drive device installed thereunder; the seat and the leg rest are connected through a linkage bar set, wherein the drive device can drive the linkage bar set to fold out the leg rest from below the seat. The backrest is disposed in one side of the seat; the backrest is pivoted to a sliding plate; the sliding plate is connected to the drive device. The drive device is controlled by a controller; the leg rest is pushed by the linkage bar set, which is driven by the drive device, and folded out from below the seat. At the same time, the drive device synchronously drives the sliding plate to move, making the backrest to recline synchronously and to create an effect of reclining/lying.

Various embodiments relate to an apparatus for adjusting a height of a resting plate comprising: a hydraulic means configured to support the resting plate, and configured to move along an axis to adjust the height of the resting plate; and an activator connected to the hydraulic means, and configured to activate and control the hydraulic means to move along the axis to adjust the height of the resting plate, or deactivate the hydraulic means to stop at the adjusted height, based on first external force on the activator.