The office chair is composed of seven components: the seat, gas rod, backrest, base, casters, five-star base, and armrest (Figure 6-77). Depending on the usage location and method, chairs are generally either fixed or sliding. The connection between the caster or fixed seat and the chair legs can be in one of two ways: threaded or spring clip embedded fixed. The sliding casters adjust to the hardness of the floor surface to control the chair's speed, enhancing safety. On hard floors, soft wheels (PU) are used, while on soft floors, hard wheels (NYLON) are employed. The primary function of the chair is to support the user's body in both working and resting positions. Office chairs, however, are designed for use in both states, featuring tilt and height adjustment functions to meet these requirements. The height adjustment is achieved through the gas rod, while the tilt function is facilitated by the tilting mechanism of the base.

Office workers spend nearly eight hours a day sitting in office chairs, becoming "professional sitters." Ergonomic studies reveal that poorly designed chairs not only hinder work efficiency but also easily lead to fatigue, which can further cause back pain or spinal disorders, becoming one of the main causes of back injuries. These diseases are often slowly developed and not easily detected early, thus missing the opportunity for timely intervention. However, these phenomena can be significantly improved through ergonomic designs, which help reduce stress, avoid work fatigue, and serve as assistive tools to enhance work efficiency. The research in human engineering during the 1990s brought a major breakthrough in chair development, shifting the focus from mere aesthetic design to the essence of sitting and the movements of the sitter. Swivel chairs extensively incorporate ergonomic principles in their seat and back designs.
(1) Seat cushion
When seated on Zhang Shutong's chair, which is designed to match personal work height, ensure that the Han Street can be placed flat on the footrest of the陵 chair, and use the pneumatic lever to adjust the height of the chair seat.
(2) Backrest
The curved back and armrests of the chair, designed to mimic the human form, can greatly alleviate fatigue and enhance comfort. A chair that conforms to human ergonomics must have a lumbar support in the backrest to support the lower back vertebrae, maintaining the natural curve and avoiding harmful twists. Generally, a backrest inclined 15° backward helps mitigate lumbar deformation.
In various work environments, adjusting the backrest angle can help users improve their posture to reduce back strain. The chair can adjust its forward tilt to accommodate the user's body movements, providing correct seating posture and reducing pressure on the lower back. The seat can also be locked into a forward tilt position, which is beneficial for users who work long hours at a computer, allowing for a greater range of motion for the lower back and reducing pressure. The smooth-rolling casters enable users to move quickly within a range, facilitating easy chair movement and seat adjustment. Models like T-1, which conform to the natural curvature of the human back, and 80-2, can help alleviate work-related fatigue. For instance, during phone calls or meetings, the swivel and recline of the seat and backrest further assist in relaxing the stress of work. Adjustable armrests can also be considered for users who work long hours at a computer, providing a more correct and comfortable working posture.