Design chair should consider the distribution of weight principle And that will be easily controlled in sitting posture should be adjustable chair both ความสูงและ inclination The good chairs to the seat.The weight should fall, tail end, not on the femur. The height of the chair should not be as high as the distance between the ground to the base leg. Because the tissue thigh couldn't stand the pressure like tissues sciatica or buttocks.Which may cause a painful stomach area. The chair is too high pressure falling to the thigh, leg numb. And if the seat is solved by moving the hips forward and leaned back seat which is not comfortable sitting positionใ And back pain.When the forearm and arm hanging down in position 90 degrees and forearm armrest must not disturb the movement in her work.