Chapter 25. Ergonomics in the Workplace

Table of Contents

The Working Environment
The Right Desk
Sitting Correctly on the Right Working Chair
Good Lighting for Productive Work
Optimum Climate
Too Much Noise Causes Stress
Office Equipment
Buying a Screen
Screen Location
The Keyboard and the Wrists
Liberating the Mouse
Links and Literature


This chapter is a short discussion of the ergonomic issues involved in the layout of computer workplaces. This text should not be seen as a substitute for studying the respective standards. No citations from these are included here and footnotes with references to other literature are completely omitted to preserve readability. It attempts to summarize the latest research findings in a short and concise manner, however, much will remain unmentioned. The items referred to in each section are mostly gathered from German literature and are almost always based on regulations and policies in the Federal Republic of Germany. This information is still useful in designing an ergonomic work area.

The Working Environment

If ergonomics specialists examined the home workstations of computer users systematically, they would find many problems. Unfortunately, no standard has yet prevented individual users from buying so-called “special computer tables”. The low-priced metal-tube frames with “practical rollers” (little stability), “ergonomically retractable keyboard tray” (no wrist pad), “integrated PC case holder and printer stand with paper shelf” (little stacking space and sometimes little legroom), “swiveling mouse pad” (unstable and insufficient working space), and “good view of the screen” (too close, too high) allow you to use a computer for a short time only. They should not be used at professional terminal workstations as they hardly meet any criteria of the corresponding standards. You will not find much of this kind of computer furniture in professional computer equipment catalogs, because manufacturers indirectly keep an eye on the employees' health by observing the minimum standards of computer workstations. Even these minimum standards should be improved.

The Right Desk

A table at the wrong height strains arm and back muscles. The resulting cramped posture especially strains the spine. Too little leg room can force an unnatural body posture and cause disorders to the blood supply.

Choosing the right table is very easy. It should be as wide and deep as possible. An individual adjustment of the table height would be optimal. Working tables at which you can change between sitting and standing by turning the table into a writing stand, often just at the push of a button, are a luxury, but changing between a sitting and standing position brings relief.

  • The flexible arrangement of working materials requires a table top of at least 160 x 80 cm.

  • Workstations made of several interlinked boards are recommended.

  • Tables that cannot be vertically adjusted must be 72 cm high. Tables that are vertically adjustable must be between 68 and 76 cm high.

  • Even more width is needed for certain working tasks, such as CAD workstations. When changing between screen work and other kinds of work, at least 200 cm is required.

  • There should be at least 60 cm leg room. Previous experience has shown, however, that this leg room is often too little.

  • When using large screens, tables should be 100 or even 120 cm deep.

  • The table surface should not be in bright colors and should have minimal reflection. A lot of office furniture is available in a subdued grey only.

Sitting Correctly on the Right Working Chair

Sitting in a working chair makes you sit in the same posture for a long time, unlike in an easy chair where you can move around easily. Constant sitting in the wrong position, such as bending forward or twisting to the side, can harm the respiratory and digestive organs. This leads to premature fatigue, circulatory disturbances, and backache resulting from overstraining the spine and the vertebrate disks. In extreme cases, years of sitting in the wrong position can lead to muscular and skeletal illnesses.

Correct sitting means a frequent change of posture. Different parts of the body are then constantly being used. Basically, it is a question of the correct adjustment. The height of your working chair is best when your forearms lying on the table are at right angles to your upper arms. You should be able to place your feet completely on the floor and your thighs and lower legs should also be at right angles. Gymnastic balls and balancing chairs offer an alternative to conventional seating arrangements.

Unfortunately, a good chair, constructed according to ergonomic criteria, is relatively expensive, but the investment in your health is worth it.

Important features of a good chair include:

  • a backrest reaching to the shoulder blades and with an adjustable kinetic resistance

  • support for the lumbar spinal column

  • a seat that is also adjustable and can be tilted forwards or backwards

  • automatic regulation of backrest and seat to retain an ideal angle

  • springs that softly cushion the weight when sitting down

  • stability provided with the help of at least five foot legs with rollers that are restrained when you stand

  • adjustable height of the seat (according to standards, 42 to 53 cm) and backrest

  • individual adjustment of arm rests, if there are any (luxury)

  • a footrest if your feet do not reach the floor

Good Lighting for Productive Work

Generally speaking, workplace lighting does not come close to the intensity of light outdoors. This difference is unnoticed because the human faculty of perception is very flexible. The influence of lighting conditions on our own efficiency is often underestimated. If the light is too bright, you cannot see what is on the screen. If it is too dark, sharpness of vision decreases. The wrong lighting overstrains the visual system and, eventually, causes symptoms of fatigue and stress.

It is assumed that a combination of general lighting and individual workstation lighting is best. For the workstation at home, the combination of a high-powered ceiling lamp (500 watts, preferably with a dimmer) and one or two workplace lamps is recommended. The fluorescent lamps usually found in offices for general lighting should be supplemented by individual workstation lamps. The lighting should, however, not be too intense and be individually adjustable. Stark contrasts should be avoided. Be careful with strong desk lamps. Good illumination is, unfortunately, very expensive and the minimum requirements of lighting can also be fulfilled with cheaper illumination layouts.

  • It is important that you are exposed to daylight. A view outside is important.

  • General lighting is considered pleasant if it is not below 250 lx (usually 500 lx is required, 1000 lx for an open plan office).

  • 500–750 lx should be emitted by the individual workstation lighting. However, individual lamps are often problematic. If they are too strong, the contrast to the general lighting is too great. Harmonic, soft transitions are considered more pleasant.

  • The lighting should not flicker. In the case of worn-out fluorescent lamps, a flickering can sometimes be noticed from the corner of the eye.

  • Avoid dark shadows.

  • Ceiling lights should emit light diagonally from above. Lighting strips should be set perpendicular to the screen table. The line of sight at the screen table should thus run parallel to the lighting strips.

  • Whether the lighting is considered to be pleasant depends on the color temperature and light color of the lamp type. Warm white or neutral white is recommended.

  • The light requirement depends not only on the working task, but also on age: older people need more light. The fact that older people often have only a small lamp in their homes has nothing to do with their light requirement, but rather with the fact that they want to save electricity.

  • A screen workstation near daylight requires optimum shielding against direct and reflex glare, especially when the line of sight is directly out the window or at a 45 degree angle to it. The built-in antiglare facilities should be variable. Under no circumstances should artificial illumination cause reflex glare on the screen.

Optimum Climate

The room climate determines our well-being to a great extent. Problems arise more often if it is too cold, too warm, too drafty, or too dry. Low relative humidity can lead to burning eyes, dry mucous membranes, skin irritations, and increased susceptibility to colds. Things get complicated when people who work in the same room are accustomed to different base temperatures. For your well-being, it is important to observe the recommended basic values for temperature and humidity and to avoid strong air movement. The working material itself should not contribute to the increase of temperature.

  • For activities in a sitting position or simple work, a room temperature of 20 to 22 °C is recommended. In summer, the temperature should be 26 °C at the most. This value should only be exceeded for a short time when the outdoor temperature is higher.

  • A lot of equipment, as well as people, emit heat and influence room air conditions. This should be reduced as much as possible.

  • The air humidity should be between 40 (sometimes 50) and 65 percent and should be checked. This value is especially affected by heating systems.

  • Draft (possibly from open windows and doors or air conditioning) should not exceed 0.1 to 0.15 m/s. Draft on individual parts of the body should be avoided.

  • An air conditioner should be individually adjustable. It should be serviced regularly.

  • The windows should be able to be opened and have sunshades to avoid glare effects. Sunlight can increase the room temperature considerably. Sunshades attached to the outside of the building provide the best protection.

  • Plants can improve room conditions and are therefore recommended in all cases. They increase the relative humidity and filter pollutants from the air.

Too Much Noise Causes Stress

Lärm ist ein körperlich wirksamer Stressor, der psychischen Stress auslöst. Auch wenn er oft verharmlost wird, zu viel Lärm macht krank. Neben gesundheitlichen Beeinträchtigungen wie Schwerhörigkeit, vegetativen Störungen und psychischen Veränderungen beeinträchtigt Lärm über die Konzentrationsfähigkeit unser Leistungsvermögen. Außerdem kann durch Unzufriedenheit die Arbeitsmotivation sinken. Problematisch ist ferner, dass eine vernünftige Lärmbekämpfung unter Umständen sehr viel Geld kosten kann.

A calm working environment improves efficiency. Work at terminal workstations is often characterized as “mental activity”. Therefore the maximum load value for scientific work or programming is 55 dB (A). The dB (A) represent a weighted evaluation of the acoustic pressure. The A-filter curve most resembles human perception. An increase of the sound level by 10 dB (A) is normally perceived as a duplication of volume.

  • Because mainly mental work is done at terminal workstations, quiet working materials should be used from the start.

  • The maximum limiting value for office work is 55 dB (A). With especially high mental demands or necessary communication of language, as low as 35–45 dB (A) is required. This is the case, for instance, for specialized work, scientific work, or programming.

  • Furthermore, the evaluation level of a maximum of 55 dB (A) is important. If 70 dB (A) is measured for a quarter of an hour, the noise in the remaining time should be less than or equal to 55 dB (A).

  • Workstations can be equipped with partitions, sound-absorbing floors, appropriately wallpapered walls, curtains, and other sound-reducing features.

  • Loud working equipment, such as matrix printers, should be installed in sound-absorbing cases. The permissible noise levels for office equipment are determined in the DIN standards.

  • An air conditioner should not increase the normal noise level.

  • Strain caused by excessive noise can also be reduced by an organizational restructuring of work.