Office Ergonomics or The Lack of It : Part II
Continues from Office Ergonomics or The Lack of It : Part I
After working on the laptop for an hour, I get headaches and neck pains. However, if I use the desk top, I seem to be able to work longer without discomfort.
The use of laptops for work is widespread. However, the screens on laptops are too low without having the head in a forward position. In the head forward position, the upper cervical is in extension and C1-3 are compressed.
As C1-3 refer to various parts of the head, clients perceive the pains as headaches. Ideally, the first line of the computer screen should be at eye level and this is easily solved by using a laptop riser that can be purchased from computer shops. It must be noted that typing on the keyboard that is in the incline position can result in carpal tunnel syndrome and wrist pains. We recommend that clients purchase and use a separate keyboard to minimize injuries to the wrist.
Along with the low screen, the laptop keyboard is smaller than a standard keyboard. With a smaller keyboard, the user’s shoulders are protracted and adducted, leading to future risk of injury to the shoulders and neck. Ironically, manufacturers are now reducing the size of laptops aggravating the situation further.
There are contentious issues with some of the ergonomic guidelines. One such issue is the hip angle of the user. It is now recommended that the hip angle should not be at 90 degrees, but between 110-130 degrees. This is because it is found that the discal pressure in the lower back reduces as the hip angle increases, which follows that ideally that the chair should be adjusted such that a hip angle of 130 degrees is achieved. However at that angle, the cervical spine has to flex forward for it to be in an upright position thus affecting the superficial cervical flexors like the sternocleidomastiod muscle. It also increases loading at the C6-T1 level. Both these factors can lead to cervical pains.
Therefore, in the case where chairs are without head rests, perhaps the user should adjust the hip angle to 110 degrees. If head rests are available 130 degree hip angle is fine as the head is completely supported. Another point to note is the user’s primary complaint. If the main problem is in the cervical spine, positioning the hip angle at 110 degrees is preferred.
Another issue of contention is the use of a tray table for the key board. Some would argue that a tray table is essential and that key board should never be placed on the table. The rational for this argument comes from having the shoulders dropped and relaxed while working as most table tops are too high. However, the drawback with the tray table is the lack of room for the mouse. The mouse should always be placed right next to the keyboard to minimize out stretching of the arm.
In essence, although ergonomics is about maintaining the ideal body posture while we work, this should be achieved with as little physical effort as possible. How this is done is open to one’s creativity and presenting situation and environment. Ergonomics is very personal, the guidelines are readily available but there are no hard and fast rules. Adopt them only if it feels right for you.
Lohman, TG, Roche AF, Martorell R (Eds). Anthropometric Standardization Reference Manual. 1988 Champaign, IL;Human Kinetics