In industrialized countries, many people sit for most of the time that they are awake. They sit while having breakfast, while going to work in cars or buses, in school classrooms, in meetings, in offices, during dinner, and at home while watching television. Many people also sit at work operating machines which new technology has developed to replace manual work.
Although sitting requires less physical effort than standing or walking, it puts a lot of stress on lumbar area. Combined effects of a sedentary lifestyle, and a job that requires sitting can lead to many health problems. The selection of a suitable chair is a critical step in preventing health problems in people who work in a sitting position. However, you do not have to spend a lot of money to find a proper ergonomic chair.
A good ergonomic chair will have basic adjustability features. The features that should be considered include:
Seat height adjustability: Adjustability is a must – feet should rest comfortably on the floor without pressure on the back of the thighs. When seated, your hips should be slightly higher than your knees. To achieve proper height with respect to your desk or keyboard tray height, you may need a foot rest.
Seat depth adjustability: The depth of the seat is important in order to reduce pressure on the back of your thighs or calves. If the seat puts pressure on the back of the knee, or mid posterior thigh, this will reduce circulation and cause a pooling of blood in the extremities. This can lead to varicose veins, painful conditions, and also blood pressure issues over time. Proper seat depth will allow for a 2-3 finger width distance from the back of the knee to the edge of the chair.
Armrests (height adjustable): To reduce strain on your neck and upper extremities, your armrest height should be as follows: with the arm relaxed and bent while seated, the arm rest should be a 2 finger width higher than the bottom of the bent elbow. Armrests set too high will cause compression of your thoracic outlet. Armrests set too low will cause traction on your neck. The length of the armrests may need to be considered as well so they do not prevent you from pulling in close to your desk or keyboard tray. Armrests set approximately 15cm back from the edge of the chair should be adequate.
Back rest height: A mid back or high back chair offers more support and will reduce lumbar strain. A low back chair is not recommended if you spend a fair amount of time sitting. Regarding shape of the back rest, do not get hung up on molded forms and fancy adjustable parts. The most important factor in reducing back discomfort while sitting is the ability to move around frequently. A chair should not lock you into a position and restrict your movement.
Many of the features described here allow a chair to adjust to a given posture or body size, but it is important to remember the importance of posture change. Adjustability features should allow, rather than inhibit, free posture change. Sitting increases the mechanical force applied on your body.
Stationary postures cause tonic muscle contraction which means they are constantly contracted. This does not allow for the muscles to rest, or allow blood flow. Therefore, by not altering postures or taking short frequent movement breaks, you are at risk of experiencing mechanical pain conditions and excessive muscle tension. Therefore, move around or fidget in your chair frequently, and get up and move around at least every half hour. Your movement breaks do not have to last long, but they do have to be frequent in order to minimize your chances of experiencing discomfort.