Ergonomics 4 Schools

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Workspace

What is workspace?

Workspace is the space within which you perform the tasks that add up to your job. If you were cooking dinner (unlikely!), your workspace would be the area in the kitchen around the fridge, cooker and sink. While you are reading this, your workspace includes your desk and chair and the area immediately around them.

Physical design of a workspace includes working out how much space needed, and positioning of furniture, tools, equipment and any other items needed to perform the tasks, in respect of posture, access, clearance, reach and vision of the user.

A poorly designed workspace, or a bad arrangement of furniture or equipment, may result in injuries and strains due to adoption of uncomfortable working postures, less 'spare' capacity to deal with unexpected events or emergencies, the increased possibility of errors or accidents, and inefficiency (the dinner takes longer to cook if your kitchen is badly organised!)

Examples of workspaces
 

Workspace factors

You should find the answers to the following questions when designing workspaces:

  • What type of task will be carried out and what specific actions are to be used to complete the task?

  • Will the potential users of the workspace (your user population) be seated or standing?

  • What postures will the users have to adopt?

  • What are the relevant body dimensions of the users? These dimensions can be found in anthropometric tables. (Read the anthropometry topic for more information.)

  • Do you need to design using minimum, average or maximum dimensions?

  • How far can the users reach, horizontally and vertically?

  • What are the visual aspects of the task?

It may also be necessary to consider factors such as how long the task will take, the environmental conditions that the task is performed under (lighting, temperature, noise levels), and the experience that the users have of performing the task.

 
 
 

Body dimensions

Using anthropometric data

People vary both in their body dimensions and proportions. Body size varies with age, gender, nationality, ethnic origin, occupation (as people of a certain size are often more suited to certain occupations, for example, truck drivers tend to be larger males), as well as other factors such as body type (muscular, thin etc) and disability. It is critical that when you are designing for a specific group, you must use workspace data that is specific to them. In general, this tends to be a broad spectrum of users. However, a workspace may be designed to be used by a restricted group of users, for example, drivers of fire fighting vehicles (mainly male, 30-50 years old), or be designed to be used by the majority of the adult population, for example, drivers of private cars (both male and female, 17-70+ years old). 
Allowances should also be made if special clothing or personal protective equipment, such a hard hats or gloves, needs to be worn. These may restrict motion and reach in certain directions, or require greater clearances, for example, people who need to wear boots will need more foot room.

Designing for the 'average'

It is important to realise that there is no 'average' individual. You may be 'average' for one or two body dimensions, say arm length and height, but generally that is all. Designing for the average user is often seen as bad design, as it only accommodates 50% of a population, however, there are a few cases where it is appropriate. Designing for the extreme or with maximum adjustability may not be practical, and designing for the 50th percentile may be the only way to reach a compromise with other design factors, for example, cost, time and space. An example is the counter height on a supermarket checkout. This is designed for the 50th% percentile because it is important for it not to be too high OR too low, and because adjustability is not feasible.

Designing for adjustability

Wherever possible, it is best to design adjustability into any workspace. An example is the interior of a car, where the driver's seat has height adjustment, and forwards and backwards adjustment, to comfortably fit as many users as possible.

For an adjustable range, we generally use:
- 5th percentile female for the lower limit,
- 95th percentile male for the upper limit.

Designing for extreme individuals

In some situations a specific dimension of a workspace layout becomes the limiting factor that may restrict the use of the workspace for some people. This limiting factor can either be designed for the minimum or maximum value for a population, depending upon what is required.

Design for the maximumYou should design for the minimum population when the minimum value (lowest) of the feature has to accommodate all users. For example, controls should be within reach of the smallest operator.

You should design for the maximum population when the maximum value (highest) of a feature has to accommodate all users. For example, the height of a doorway should allow all users to pass through without stooping or banging their head! 

It is not usually practical to design layouts for all users (100%), so when setting the dimensions for a workspace layout use:
- 5th percentile female for minimum values,
- 95th percentile male for maximum values.

 

Reach - the workspace envelope

A 'workspace envelope' is a 3-dimensional space within which you carry out physical work activities when you are at a fixed location. The limits of the envelope are determined by your functional arm reach which, in turn, is influenced by the direction of reach and the nature of the task being performed. Most of the things that you need to use to carry out your tasks should be arranged within this area. Workspace envelopes should be designed for the 5th percentile of the user population, which means that 95% of users will be able to reach everything placed within the envelope.
Seated workspace Standing workspace
In general, the maximum work area is the area within comfortable reach of your extended arm, while the normal work area is within the limits of a comfortable sweeping movement of your arm, with your elbow bent at a right angle or less. You should also consider any potential restraint caused by clothing that you might have to wear, as well as personal factors such as age, gender (women have greater flexibility than men), and any disabilities.

The type of task being performed also affects the boundary of the workspace envelope. For tasks that require the activation of a switch, it is common to use anthropometric measurements from the fingertip reach of the users to set the envelope boundary. However, where a grasping action is involved, the reach of the user is reduced as your fist has to be clenched.

The limit of the workspace envelope for a standing user can be seen as the space in which an object can be reached and gripped comfortably, when you are standing up straight.

Your arms and hands are most powerful when your elbows are close to your sides and bent at right angles or more, that is, extended slightly. The work surface should allow this kind of posture for manual work requiring strength.

For precise, fine work, as well as for writing, drawing and reading, the work surface should be higher so that the elbows can be rested on it. This will also bring the work closer to your eyes.


Seated reach

Anthropometric estimates for British adults
aged 19-65 years (in mm, from Pheasant)

Dimension 5th %ile 50th %ile 95th %ile
A Max head height  -  - 1450
B Work surface height 660 710 760
635 685 735
C Shoulder-grip length (max working limit) 610 665 715
555 600 650
D Elbow-fingertip length (normal working limit) 440 475 510
400 430 460
E Sitting eye height (above seat surface) 735 790 845
685 740 795
 
MALE FEMALE

For seating dimensions, see the seating topic.

Anthropometric estimates for British adults
aged 19-65 years (in mm, from Pheasant)

Dimension 5th %ile 50th %ile 95th %ile
A Standing height (stature) 1625 1740 1855
1505 1610 1710
B Eye height 1515 1630 1745
1405 1505 1610
C Elbow height 1005 1090 1180
930 1005 1085
 
MALE FEMALE
Some general principles for seated work:
  • Working with relaxed upper arms and elbows at approximately 90 provides comfort and helps maintain straight wrists, which reduces the strain of repetitive tasks.
  • Adjustable height work surfaces allow each user to fit the work surface to their own needs. If this is not possible, fix the work surface height to be at a level that places the working item, for example, a keyboard, at elbow height.
  • Make sure that there is adequate clearance for your thighs under the work surface.
  • Small users whose feet do not touch the floor when seated should have a footrest.
  • For fine work, requiring better visibility, the work surface can be raised, but elbow support must be provided.
Some general principles for standing work:
  • For work that requires the application of force from the shoulder and back muscles, the work surface should be about 100-250mm lower than the level of the elbows.
  • For normal tasks that do not require much strength, the worktop should be about elbow height or just below.
  • For precision work, the work surface should be about 50-100mm above elbow height.
  • Precision work should preferably be done sitting, when the back muscles should be supported and relieved by suitable seating and elbow support. The provision of high stools allow users to alternate between a standing and a 'perched' position.
  • Adjustable height work surfaces allow each user to fit the work surface to their own needs. If this is not possible, design for the largest user, and supply platforms to those that are smaller.

Maximum vertical and horizontal reach

Vertical reach is limited by how far you can reach and grasp objects above or below your shoulder height without stretching or bending. Measurement of vertical reach is taken from the surface of your shoulder to the centre of your closed hand (or extended middle finger for button operation). Height of reach is used when positioning shelves for storage, handles or controls above head height.

Horizontal reach is measured in the same way, but about the horizontal plane.


Visual workspace

We alter our direction of gaze by moving our eyeballs within their sockets and by moving our head. It is good to have some movement of the head during work in order not to tire the neck muscles. The head is supported by the effort of the muscles in the neck. If you hold your head still, you muscles are doing static work, that is, they are working continuously with no breaks to rest. This is more tiring than if you move your head, when the muscles are doing dynamic work, and muscles groups get a chance to rest as others take over. Therefore, the visual aspects of the workplace should be arranged to cause the lowest level of static work by the neck muscles.

Visual accessVisual accessYou should aim to position frequently viewed items within a comfortable zone in front of you. This is normally within 15 above, or 30 below, the horizontal, and 15 to the left and right. In the normal, relaxed position of the head, neck and eyes, the line of sight is about 10 to 15 below the horizontal, therefore, viewing horizontally straight ahead actually requires a small amount of effort.

Distance is also a factor in visual fatigue. Visual displays are comfortably viewed from 500-750mm or more, depending on the size of the display components. The lens of the eye stiffens as people get older, altering the distance at which they can easily focus, so objects need to be positioned further away for clear viewing. They also take longer to focus on things (it will happen to you one day!).

Access

Clearance

When you are designing a workspace, you must also remember that you need access to it and to be able to move around within it. For example, you need to allow at least 600mm width for a person to walk normally down a corridor, and 1200mm for two people to pass side by side. You should allow 1200mm from the front edge of a desk to push a chair back and stand up, with no restrictions.

The space that you need to move around freely in can often be more than you think. Try standing with your back against a wall and bend forwards. You won't be able to bend far before you start to fall forwards, as your centre of gravity falls outside the area of your feet. You need to move away from the wall to allow yourself to move your bottom backwards to counterbalance the weight of your upper body. How far do you need to stand away from the wall before you can bend over without restriction? Is it further than you thought?

Sometimes people have to work in, move through, or access restricted areas, for example, for maintenance work. Clearance can be seen as the minimum distance required to allow the desired user group into, or through, an area. This is especially crucial for the design of features such as escape hatches and emergency exits. Some examples are:

  • The minimum vertical space between the floor and an overhead obstruction must allow for the tallest user plus their footwear and headgear.

  • The minimum horizontal space between two obstructions  must allow for the widest user plus room for movement and equipment.

  • A hazard must be beyond the reach of the user with the longest arm, if there is no room to bend.

  • Grille openings in front of a hazard must not allow reach to the hazard by the user with the longest or thinnest finger.

Working out how much total space you need

Guidance on the Workplace Regulations states that work rooms should have enough free space to allow people to get to and from workstations and to move within the room easily. The number of people that may work in any particular room at any one time depends not only on the size of the room, but on the space taken up by furniture, fittings, equipment, and on the layout of the room. The total volume of the room, when empty, divided by the number of people normally working in it should be at least 11 cubic metres. In making this calculation, a room or part of a room which is more than 3.0m high should be counted as 3.0m high. Can you work out how much room you each have in your classroom (don't forget to include your teacher)? What is the maximum number of people that your classroom could accommodate comfortably according to these calculations?

 
Legal requirements for workspaces

The main set of UK regulations concerning workspaces are the Workplace (Health, Safety & Welfare) Regulations 1992. Specific ergonomic standards include ISO 9241 Ergonomic requirements for office work with visual display terminals, and ISO 11064 Ergonomic design of control centres.

  

 

Guidelines for the design of workspaces
 

 
  Encourage a frequent change in posture
People involved in seated work should be encouraged to change posture and sit in a variety of positions. Most modern office chairs help to promote this sort of behaviour. For industrial tasks, 'sit-stand' workspaces are advisable, whereby the task is set at a height that is suitable for standing at, but a high stool is also provided for support.

Avoid forward bending of head and trunk
This is common during visual tasks, and where the work surface is too low. For fine visual work, consider sloping the worksurface towards you.

Avoid causing the arms to be held in a raised position
This is common where the work surface is too high, or the seating is too low. If, usually for visual reasons, the task should be performed in a raised position, then elbow support should be provided. A lack of support leads to stress on the shoulder muscles, and an extra circulatory burden on the heart.

Avoid twisted and asymmetrical positions
These are most common when displays or controls are poorly located. Frequently used items should be placed centrally between waist and shoulder height to reduce the need to bend or twist to reach.

Avoid postures that require a joint to be used for long periods of time at the limit of its range of motion
This is particularly important for the wrist and forearm. Make sure that items that are often used are within easy reach.

Provide adequate back support for all seats
If, due to operational reasons, the user is not using the back support, it should still be provided in order to give support during rest periods.

Where muscular force must be exerted the limbs should be in a position of greatest strength
The muscles and joints work best when they are in the mid-third of their range. Position items so that the arms can be used in this way.

Test your workspace layouts
Make sure that you have designed the workspace well by trying it out on a range of users performing relevant tasks.

 

 

Workspace FAQs

Q. How can I use ergonomics when designing an internet cafe? Answer

Q. I'm doing a project on schools desks for 6 to 8 year olds. What are the basic specifications on this? Answer

Q. Is a knowledge of ergonomics a prerequisite for successful plant layout?  Answer

Q. Where can I find information about about the optimum amount of living space needed, or recommended when designing houses and room layouts?  Answer

Q. I am interested in applying ergonomics in my classroom. I bought some coloured and mobile furniture for my classroom, so the kids can move and arrange it in different ways. Could you please help me with some ideas regarding this problem? I would also like to use ergonomics to stimulate kids imagination and to ease the process of learning.  Answer

Q. I'm interested in ergonomics in hotels for my master thesis. In Italy there aren't reports in this subject. What could you suggest to me?  Answer

Q. What kind of ergonomics would I use in the kitchen?  Answer

Q. Why is it important to have a ergonomically friendly school?  Answer

Q. Can soldiers in tanks go to the toilet anywhere without getting out? My teacher thought they would not think about going during a battle but I thought they might.  Answer

Q. I am designing a bar and would like any information about the ergonomics of comfortable leaning (as in when leaning on a bar).  Answer

           
Reference
Pheasant, S (1998) Bodyspace. Anthropometry, Ergonomics and the Design of Work. (2nd Ed.) London: Taylor & Francis ISBN 0748403264

Acknowledgments
Content: Samantha Porter & Shayal Chhibber
Images: IMSI's MasterClips Collection