Are you sitting well? An introduction to proper chair ergonomics
But did you know that standing all day is also bad for your health? Prolonged standing while working “can cause sore feet, swelling of the legs, varicose veins, general muscular fatigue, low back pain, stiffness in the neck and shoulders, and other health problems” (CCOHS).
So, what is the correct position for work? Ideally, a workstation should allow for workers to alternate between sitting and standing positions throughout their work day. Movement between positions exercises muscles and increases circulation, which helps energize the body and mind. It’s been studied that even slight movements, like standing up every now and then, improve memory, attentiveness, learning and ultimately cognitive performance.
The solution to maintaining an ergonomic working position is pairing a height-adjustable table with a chair or stool that is suited to the worker and the work being done. A workplace chair must be equally good fit for anyone and everyone – men and women, small people and large, heavy and light, and young and old – which is why it is essential to have a sufficiently wide range of settings and adjustments.
Here are a few features of a good workplace chair:
Suitability for the measurements of the person/user – Adjust the chair, not the person
Supports the person in various working postures – Unsupported sitting in an upright posture results in 40% increase in disc pressure compared to standing. May include a synchronous mechanism.
Promotes lumber lordosis – Utilizes a backrest for the lower back and has a tilting seat
Minimizes static loading of the back muscle – for example, using a reclined backrest
Easy adjustability – An adjustable work seat promotes productivity and reduces pains in shoulders and in the back
It is not enough to pick a well-designed chair. A worker should adjust the chair to fit their body. Below are a few adjustment factors to consider when selecting a workplace chair:
- Seat Height – Allows adjustment to body size and height of workplace. The seat is at the correct height when the upper arms and forearms for a right angle and the forearms are level with the working surface. At the same time, the angle between the thighs and lower legs should be at least 90 degrees. The feet should be flat on the floor or on a footrest.
- Seat Tilt – Many jobs are carried out in slightly raised positions, and require people to bend forwards. A correspondingly tilted seat provides a seat angle of at least 90 degrees, while at the same time providing contact with the backrest. A forwards-tilting seat reduces the stress in the lower back. The seat should slightly be inclined forwards for jobs involving fine motor skills.
- Seat Depth – Matches the depth of the seat to the size of the body, giving the best possible contact surface for the thighs. The bottom should be right at the back of the seat to fit its anatomically shaped contours. Only this posture ensures a contact with the backrest so that the user benefits from its support. The front edge of the seat should be optimized for the length of the thighs, and not press against the lower limbs.
- Backrest Height – Ensures that a person is ideally supported – especially in the lumbar region – no matter how tall he/she is. Adjust the backrest so that its curvature supports the spine in the area of the 3rd and 4th lumbar vertebrae (approximately belt height).
- Weight Regulation – By individually adjusting the pressure of the backrest, both light and heavy people can sit with the correct posture.
- Permanent Contact Backrest – follows the movements of the upper body, and ensures that the back always remains fully supported. Ideal for people who must lean forward for long periods of time, with only a small distance between eyes and workplace (e.g. working in precision engineering or in the laboratory).
- Synchronous mechanism – provides an active-dynamic sitting experience with weight regulation. The seat and backrest accompany to body as it moves. This gives the user a feeling that can best be described as “weightless floating”. The synchronous technology comes into its own where users are working at office type working situations, working at a screen, or constantly changing their sitting position.
- Armrests – Armrests have the important function of reducing the strain on the upper body and arms. The height, and width of 3D armrests can be adjusted, and can also be swiveled. In addition, armrests can feature depth adjustment. Upper arms should be close to the body, shoulders relaxed, and forearms should rest naturally.
While we have discussed seated and standing positions, there is a third position to consider. Semi-sitting, as the name indicates, is a position between standing and sitting, that allows a worker to stand for prolonged periods without any signs of fatigue by supporting a person’s posture without forcing them into a position. Standing rest takes off 60% of your body weight from your feet compared to standing. Using a stool or a saddle chair creates a 135-degree angle between the thighs and the upper body, which improves blood circulation in the hip and knee joints.
How to choose a sitting or standing work position?
If tasks require paperwork, typing, no heavy lifting, and/or all tools for the job are provided in arm’s reach, then the workstation should be designed for sitting, but with possibility to stand. Latest cognitive research shows how beneficial changing working posture can be. It’s been studied that even slight movements, like standing up every now and then, improve memory, attentiveness, learning and ultimately cognitive performance. So, what better way to improve the efficiency of a desk-tied person?
If tasks require lifting heavy loads, continuous movement, parts retrieval, and/or there is no leg space, then the workstation should be designed for standing but with the possibility to rest every now and then, whenever possible. Do note however that even though stand up working posture is becoming increasingly popular; many official recommendations still state that proper seating ergonomics is one of the most crucial aspects of preventive actions for work related musculoskeletal disorders. Therefore, it is not indifferent how and on what you are sitting, when you are sitting!
Not sure which style chair is ideal for your working environment? Below are two charts to help you decide.
Finally, it is important to remember safety when selecting a workplace chair. Here are some tips to consider:
- A chair over 25.5” needs to have glides and a foot ring to create a safe sitting position.
- “Stop and Go” casters are a good option when a chair will be moved out of the workspace when not in use. The stopping mechanism on these casters ensures the chair will not move when the worker is sitting. It can also prevent movement during sensitive work.
- ESD chairs are available when working with sensitive parts or equipment.
- Seat material can be just as important as seat adjustment. When choosing a semi-sitting stool, for example, consider a slip-resistant material.
- Industry standard dictates a chair should conform to the DIN 68 877 requirements. Be sure to look for the GS safety mark when selecting a chair.
No matter the work being done, a workplace can greatly benefit from varying working positions. When seeking out potential solutions, consider chairs, standing rests, saddle chairs, footrests and easily adjustable workbenches, which allow for both sitting and standing work that may be most suitable for your environment and staff. And remember - a comfortable employee is a happy, and productive, employee!