What follows, is a 15 point step-by-step ‘recipe’ to systematically establish how well your workstation ‘fits’ you and where it doesn’t, what you should do to change it.

 

1              Move your chair away from your desk (this is so that you are encouraged to adjust your chair without reference to your desk height which may corrupt your judgement).

 

2              Adjust your chair height so that you are sitting with your buttocks and thighs fully supported. You should have an angle of 90 degrees in your ankles, knees and hips as shown in the diagram. Your thighs should be horizontal. It is often easiest to get someone else to look at your posture from the side, as it can be difficult for you to assess if you are sitting correctly when you are looking down.

 

3             Adjust the seat back height and angle until you are sitting reasonably upright and your back is fully supported i.e. your back is in contact with as much of the seat back as possible - take particular care with the lumbar region to ensure that the curve of the seat backrest fits into the curve of your back with as even a pressure as possible. You would want to ensure that the area near to your ‘belt-line’ was where the most support is being given.

 

4             Move your chair back to your desk and swivel it around, through 90 degrees, until your elbows are against the edge of the desk i.e. you are sitting sideways to your desk. An ‘ideal’ seated posture is one where your elbows are at the same height as the keyboard 'home row' (the ASDFGHJKL row of keys). Having done this what height are your elbows?

 

5          5 (a)     My elbows are at the same height as the keyboard home row –

 

Good, you are seated correctly; your wrists will be neutral as shown in the following diagram.

 

 

 

 

 

 

 

You can now move onto section 6.

 

If they are above the keyboard home row read section 5(c).

 

5 (b)     My elbows are below the height of the keyboard home row –

 

You need a footrest. The height of the footrest should be equivalent to the degree of the mismatch - e.g. if your elbows were found to be 75mm below the keyboard home row height then raise up your chair by 75mm and use a 75mm high footrest. The logic behind this strategy is simple; you had previously set-up your seat to achieve a viable seated posture but unfortunately your elbows were below the height of your keyboard home row. You need to ‘key’ with the keyboard at elbow height as this will give you a desirable upper limb posture – upper arms hanging vertically at your side, forearms horizontal, your wrists straight and therefore neutral (see diagram). With your arms in this position you are much less likely to suffer from problems with your upper limbs, neck and shoulders.

If you were to simply raise your seat height and not use a footrest you would find, after a short time that the seat would start to become uncomfortable as a consequence of the pressure under your thighs and the backs of your knees. The use of an appropriate height footrest will prevent this source of discomfort. You have no other option.

 

The use of a footrest will also discourage you from putting your feet on the ‘five-star’ base of your seat. Resting your feet on the seat base places a static load on the muscles in your lower leg which will also eventually cause discomfort. Therefore, do not put your feet on the seat base.

If you are one of these people who does not like the idea of using a footrest, you may be tempted to simply lower your seat to the ‘correct’ seated position. However, whilst this would result in you sitting satisfactorily, you would not be able to use the keyboard safely because your elbows would now be below keyboard height. To compensate for this you will either elevate your shoulders, splay out your elbows, work with your arms outstretched or bend your wrists. These postures are undesirable and hazardous. The diagram below shows a typical bent wrist posture of someone who has their seat set too low and should use a footrest:

  

 

The use of a footrest, when needed, is a vital part of achieving and maintaining an ergonomically desirable posture.

 

You can now move to section 6.

 

 

You need to raise the desk. The same approach applies as in the previous section, but this time the desk legs will need extending by the amount of the mismatch. This situation is very rare. The diagram below shows the typical upper limb posture of someone who needs their desk raising:

 

 

  

Clearly, if you are fortunate enough to have a height adjustable desk, you can address any height mismatch simply; set-up your chair as described and then adjust the desk height until the keyboard is level with your seated elbow height.

 

6              Having set-up your footrest/chair/desk combination you should now be sitting correctly in front of your desk. Now position your keyboard so that there is sufficient room in front of it to allow you to rest your hands when not keying. The amount of space you should have is 100mm. Resting your hands on the desk surface in front of your keyboard when keying will result in a hazardous and undesirable wrist postures. For many people, when sitting correctly, this will mean that their abdomen will be close to the edge of the desk.

In some instances, the arms on the chair will interfere with the desk such that you cannot get the chair in close enough to the desk. If this is the case, you will be obliged to move your elbows forward to reach the keyboard and this will place an unnecessary load on your shoulder muscles. Do not do this, instead remove the arms from your chair they are, in reality, of little value and are undermining your comfort and health.

 

You may believe that you can avoid taking the arms of your chair by pulling the keyboard closer to you. Do not do this because you will lose the space you created for resting your arms. Equally, do not adjust your chair height to the chair arms under or over the desk; this will undermine your upper limb posture. Assuming the arms cannot be adjusted to allow a satisfactory posture, remove the arms. Many people have found that by removing the arms from the chair they have experienced great improvements in posture and comfort and a reduction in a variety of aches and pains.

 

7              With your keyboard correctly positioned 100mm onto your desk and sitting squarely in front of you, you can now position your mouse. By slightly rotating your elbow and moving your forearm sideways your hand should naturally fall to your mouse. Move your mouse with the whole of your arm but try and keep your elbow by your side and your upper arm as vertical as possible. Do not bend your wrist to manipulate your mouse. When not using the mouse take your hand off it to relax your upper limb.

 

Do not use a mouse mat with a raised ‘wrist rest’ as these tend to encourage you to bend your wrist from side to side. If you are using a mechanical mouse, with a ball, use a mouse mat and keep the mouse, the ball and the internal rollers clean to ensure smooth and accurate performance. Preferably use an optical mouse as they no not require any cleaning to function correctly.

 

8             Once you are seated correctly and can place your hands on your keyboard and reach your mouse with ease, you can adjust the position of your DSE monitor. The DSE monitor should be positioned so that:

 

a)         the monitor is directly in front of you,

b)         your eyes assume a slight downwards cast of 15-20 degrees,

c)         the distance from your eyes to the screen should be approximately 600 mm, and

d)         the screen should be at 90 degrees to your field of view.

 

 

a)            Adjust the screen height so that, when seated correctly and looking straight forward, you are looking at the centre of the top edge of the monitor surround. With the monitor in this position you will be looking slightly downwards during normal screen use (because you generally look at the middle of the screen and not the top of it).

 

b)            Move your screen back until, when seated correctly, the screen is far enough away so that it can be touched with the finger tips of your outstretched arms.

 

c)            Tilt the top of the screen backwards slightly until the distance from your eyes to the top and the bottom of the screen is the same.

In this position, the risk of sustaining neck and shoulder ache and eyestrain will be minimised.

If you screen is too low or too high the muscles in your neck will have to work very hard, whilst statically loaded, to support the weight of your head – your head weighs over four kilos and thus considerable effort is needed.

If your screen is too close, you will find yourself backing away from it as the effort to focus on something that is too near is hard work for the eyes. Consequently, you will push your chair away from the desk and then work with your arms slightly outstretched which is undesirable.

 

If your screen is too far away, you will tend to lean forward to read the screen and therefore loose the support of your seat back.

 

Finally, if the top and bottom of the screen are at different distances from your eyes, you will make thousands of minor focussing adjustments during the day as you scan up and down the screen. The position of your screen can result in many problems apart from visual fatigue.

 

9             Once you screen is correctly positioned, look for unwanted reflections and glare in your screen. If these are present, try to reduce the problem at source by fitting blinds or alternative lighting. Consider moving or rotating your workstation. Do not change your screen position as this will create alternative difficulties.

10           Consider the use of a document holder to assist with any copy typing. Generally, the copy holder should be at the same height distance and angle as your screen to avoid unnecessary head, neck and eye movements and reduce the amount of re-focusing.

 

11           Arrange the other items on your desk according to frequency of use so that all of the items needed regularly are most easily to hand. Ancillary equipment such as telephones, pen holders, staplers etc. should be arranged conveniently within your reach and positioned according to importance, handedness and frequency of use.

 

12           Ensure that the environment suits your needs and is comfortable. Heating, ventilation, humidity, lighting and unwanted noise will all influence your performance and health.

 

13           Keep your screen and keyboard clean.

 

14           Ensure that the area under your desk is free from all obstructions so that you can move your legs and feet.

 

15           Do not put items on the floor or out of reach as it is important to avoid bending and stretching when seated at your workstation.

 

 

 

Setting up a workstation correctly is largely down to the application of a few simple principles. Once learnt, they can be applied time and time again with ease. Even if these guidelines are followed you cannot guarantee that problems will not occur.

 

It should be noted that a ‘normal’ keyboard, in terms of the part you usually type on, is narrower than the shoulders of most users. This is shown in the diagram below:

 

  

Therefore, your wrists will still be bent to the side even if you have avoided having them bent up or down by getting your elbows level with your keyboard. On the basis that any bend in your wrists is hazardous, even when you have set-up your workstation ‘ideally’ as described in the 15 point plan you have just followed, you are still not free from risk. This, coupled with the knowledge that prolonged sitting is not particularly good for your back, is why it is so important to regularly change your posture and have breaks or changes of activity.

 

Finally, other factors not covered here, such as: the task design, the software you use and your own medical history will all influence the likelihood of experiencing difficulties.  Nevertheless, it should be remembered that a DSE user who is provided with: a suitably adjustable chair, an adequately sized desk, a correctly set-up computer and software appropriate to the tast, has the use of such things as a footrest and document holder if needed, who is trained, works in a controlled environment, takes appropriate rest breaks and who works to sensible and achievable targets is unlikely to experience health problems as a consequence of their work.

 

Information provided by leading ergonomist, Michael Twiss of MTA. 

 

Please contact us to get in touch with Michael and the MTA team.