Abstract: A chair comprises a seat with a seat carrier comprising a buttock section at the rear and a knee section at the front, a height adjustment device coupled to the seat, and a foot part configured to be placed on a surface. The height adjustment device is configured to change the distance between the seat and the foot part. The seat is designed in such a manner that a height of the buttock section of the seat carrier and a height of the knee section of the seat carrier can be changed relative to one another. The chair further comprises a blocking structure configured to block the height adjustment device when the height of the buttock section of the seat carrier and the height of the knee section of the seat carrier are in a target position relative to one another.