Exam terms 2012-18

Question 1

Workspace envelope:

Answer 1

The workspace envelope describes the 3-dimensional space within which physical work activities are performed. The limits of the envelope are determined by functional arm reach and will be influenced by the direction of reach and the nature of the task being performed. The workspace envelope is specific to the tasks and environment in which the measures are made. Within the envelope, the ‘zone of convenient reach’ describes the zone where objects can be reached without undue exertion.

Question 2

Systems boundary:

Answer 2

Ergonomics uses the concept of systems – so looks to identify the components of a system, and the relations or interactions between them – and the system boundary relates to this idea of considering work systems. The boundary indicates a definition of what specific human-machine interface is, so it offers a demarcation of the area of interest. The boundary might be functional or physical depending on the system you are considering, but it is how you separate the system you are interested in from an adjacent system.
Eg. in a sawmill you might look at different areas such as the headrig where logs first enter the mill and then different stages and saws in the mill, with tables for sorting or stacking at the end. You might look at the boundaries between these areas to help define the activities, tasks or interactions taking place. It would be important to specify what the boundary to your system was to be clear about context and, for example, to offer design or performance specifications.
So this can mean that if a system is made safer, there could be an increase in risky behaviour due to the perception of improved safety, so the overall level of safety remains the same. Conversely, if a system becomes more unsafe, the perceived risk is greater, and so workers may improve their own behaviour - the risk perception is homeostatic.
From a physiological perspective, an example could be the body maintaining core temperature within a small range - and the implications for workloads, clothing etc.

Question 3

Static work:

Answer 3

muscle contraction without varying in length – i.e. sustained muscle activity without a repetitive cycle of contraction and relaxation.
Eg. The action of holding your arm out horizontally at shoulder level. In order to hold up your arm against the pull of gravity, the muscles of the shoulder region have to contract, despite the fact that to the observer there is no movement. Postural muscles, whose main function is to support parts of the body against the effects of gravity, are often ‘statically loaded’ in this way.

Question 4

Sociotechnical system:

Answer 4

describes the interaction between human and machine elements.
Managers need to consider the social and psychological impact of different social systems and job designs.
If no consideration is given to the human factor, the social systems that emerge within an organisation may not be able to operate the technology efficiently as they become characterised by low morale, increased absenteeism and turnover.

Question 5

RULA:

Answer 5

The Rapid Upper Limb Assessment (RULA) was developed to assess exposures and determine the action level of tasks thought to contribute to the development of upper limb disorders (ULDs) (McAtamney and Corlett, 1993). This technique considers postures, forces and muscle activity associated with work tasks by examining the upper and lower body postures.
In the RULA technique, individual scores are assigned due to risks associated with posture, force and muscle activity and thus allow the identification of areas which are driving risks due to less desirable conditions. When using this method for prioritisation of redesign, modifications should be focused on the areas associated with the highest scores. This technique is relatively easy to conduct and provides reliable results without specialised tools or equipment beyond the associated tables and charts.

Question 6

Rating of Perceived Exertion (RPE):

Answer 6

Borg’ Rating of Perceived Exertion scale, or RPE scale, is an outcome measure developed by Borg for rating the level of exertion during physical activity. Perceived exertion is how hard someone thinks their body is exercising, and heart rate indicates how hard they are actually working – there is a good correlation between perceived exertion and actual heart rate (60-200 bpm). The RPE is a scale of 6- 20: so a rating of 6 would correlate with a heart rate of 60, a rating of 15 to heart rate of 150 etc.
The RPE is a useful way to obtain a subjective indication of workload or fatigue – so it can be used to help estimate how hard an activity or work is (ie the level of activity intensity).
Eg. In an ergonomics application, you might get a group of people to give their RPE value at different times during the day, or during different task activities, to get an idea of how hard a job is, and identify which components might be contributing.
If someone was conducting a manual handling task with lots of awkward postures and reaches, they might rate that activity higher than part of the task where easier postures were possible.

Question 7

Precision grip:

Answer 7

in a precision grip the object is manipulated between the pads of the fingers and thumb, as in holding a pair of tweezers.
Eg. in the process of packing meat for sale in supermarkets the meatpacking staff have to repeatedly pick up and move small polystyrene trays upon which raw meat has been arranged. Because the trays are flat they have to be picked up using a precision grip. This observation would lead us to conclude that meatpackers will probably experience fatigue of the small hand muscles fairly quickly.

Question 8

Job rotation:

Answer 8

Rotation be formal→ directed by management or an informal arrangement amongst a group of workers. Job rotation is likely to be of most value when formally and carefully implemented.
Eg. a packing line which involves four workstations, respectively for filling a tin with product, placing lids on tins, inspecting tin weights, packing tins into boxes. A job rotation scheme where an operator rotates around these four stations, after one or two hours at each post, would introduce more variety, would mix active and passive activities and this would give a perspective of the entire operation. Implementing job rotation requires evaluation of job components, including the tasks, postures, forces, repetition, equipment and training.

Question 9

Homeostasis:

Answer 9

refers to the tendency for the body or systems to maintain balance.
From a systems perspective, homeostasis refers to a steady state of a system.
eg. ability to maintain operations, reduce the impact of risk on operations etc.
individuals in the workforce - workers adjust their activities to maintain a level of risk Eg. drive to the conditions.

From a physiological perspective, homeostasis is the maintenance of biological processes within a narrow range.
body temperature or heart rate fluctuate within narrow limits, even with widely varying external or internal demands.
Eg. the body maintaining core temperature within a small range - and the implications for workloads, clothing etc.

Question 10

Glare:

Answer 10

results when there is a high level of contrast between the intensity of light in the foreground and background, which results from an imbalance between the surface/object luminance levels, so the eye is unable to adapt to the difference luminance levels.
Eg. if a bright window is positioned behind a computer screen.

Question 11

Error-tolerant system:

Answer 11

Error-tolerant systems take into account human and technical characteristics in order to facilitate optimum function. ‘Error-tolerant’ designs reduce the consequences of errors without reducing the likelihood of errors.

• Systems that exclude the potential for error have to be 100% perfect - as the user is being given no scope to change it.
• Given that no system is perfect in perpetuity, it makes better sense to acknowledge it and steer the trial and error process offering a combination of error-excluding and error-tolerant features.

Question 12

Ergonomics perspective:

Answer 12

Key features summed up concisely by Sanders and McCormick (1987): designed with the user in mind

• Recognition of individual differences (diversity) in human capabilities and limitations and an 
appreciation of their design implications.
• The design of things, procedures, etc. influences human behaviour and 
well-being. (interaction with people and things impacts human behaviour)
• Emphasis on empirical data and evaluation in the design process. (fact checking)
• Reliance on the scientific method and the use of objective data to test hypotheses and 
generate basic data about human behaviour. (careful testing)
• Commitment to a systems orientation and a recognition that things, procedures, 
environments, and people do not exist in isolation. (context matters)

Question 13

Direct observation:

Answer 13

Observational measurement is when the ergonomist is the instrument of measurement with minimal interaction with the people and situations being observed.
- Assessing and measuring a system directly whilst in operation is essential for gaining understanding.
- Direct observation is usually unobtrusive, observer’s presence will influence system users. To what extent and in what direction the people are influenced will depend on how you are perceived.
Eg. are you introduced to people on the work floor by the local occupational health nurse (perceived as being ‘on their side’ perhaps) or simply escorted in with no introductions by a notorious ‘hatchet man’ from Head Office? The data collected will differ - perhaps significantly. For ethical as well as practical reasons, it is important that your involvement is understood and accepted by those being observed. Direct observation can be carried out quickly and is relatively non-invasive, but must be well planned so that the information collected is valid and appropriate.

Question 14

Archival data:

Answer 14

is the body of existing records held by an organisation, which were collected for reasons unrelated to the study in hand.
Possible data sources include:
- task data (methods, procedures, diaries, position descriptions)
- organisational data (statistics, policies, procedures, training information, reports, injury data)
- industry data (guidelines, training resources, information sheets, newsletters, research)
- academic research (refereed journals or serials, conference proceedings, edited texts)
- standards (NZ standards, joint NZAS standards, BSI, ISO)
- government bodies (guidelines, codes of practice, regulations, acts of parliament).

Question 15

Anaerobic metabolism:

Answer 15

where there is insufficient oxygen, anaerobic metabolic processes occur. Instead of carbon dioxide and water, lactic acid is produced as a by-product. Any build-up of lactic acid in the muscle can be a problem, because it irritates nerve endings which trigger off sensations of muscle fatigue or pain. For this reason, anaerobic processes, where energy is generated using the lactate pathway, can only be maintained for relatively short periods of time.

Question 16

Postural fixity:

Answer 16

An inability to achieve postural variety and maintaining static postures.
Eg. static work decreases the flow of blood through the muscle that is restricted.
This means that not enough oxygen is supplied and waste products cannot be flushed out.

Question 17

Latent failure:

Answer 17

are apparent failures in the design of organisational systems, the environment, or equipment that are often hidden until they contribute to the occurrence of errors or allow errors to go unrecognised until harm results.
Metaphor: A landmine - it’s there the whole time and may never be set off until a particular circumstance (some unlucky chap steps on it) sets it off.

Question 18

Organisational ergonomics:

Answer 18

is concerned with the optimisation of sociotechnical systems, including their organisational structures, policies, and processes.
Explanation: 
Relevant topics include communication, crew resource management, work design, design of working times, teamwork, participatory design, community ergonomics, cooperative work, new work paradigms, virtual organisations, telework, and quality management.

Question 19

Core temperature:

Answer 19

the temperature of the internal environment of the body, ideally between 36-37 degrees C.
Eg. A fundamental principle is that workers should be able to maintain thermal balance in the environment in which they are working, whilst carrying out their work. Thermal balance refers to the body’s ability to balance metabolic heat production and rate of heat loss, to achieve core temperature of approximately 36-37oC body temperature.

Question 20

Iterative design:

Answer 20

a process of design incorporating an ongoing cycle of assessment, design, evaluation, which refines a product or process.
Eg. Cycling through the stages of assessment, design, evaluation, implementing interventions, reassessment, feedback, commitment to regularly checking in that everything is running smoothly and making adjustments if its not.

Question 21

Job enrichment:

Answer 21

involves assigning individuals responsibility over some area of work.
Eg. employees might be made responsible for the quality control of their own production work and the maintenance of basic equipment. As a result of either of these changes, both autonomy and variety will increase. The job enrichment approach is an extension of Herzberg’s Motivation-Hygiene Theory. According to this theory (also known as the Two-Factor Theory), the presence of certain (motivator) factors, such as autonomy and responsibility, in jobs will result in superior performance and the experience of job satisfaction.

Question 22

Triangulation:

Answer 22

The use of more than one method to provide sufficient information and data to have confidence in assessments or evaluations is often called triangulation.
Explanation: Collected data from different sources helps to ‘triangulate’ findings and have confidence in the solutions. It is good practice to employ a number of analysis or evaluation methods in any given study, drawing on qualitative and quantitative techniques, in the field and/or laboratory settings. This is done to improve the effectiveness of the study and confidence in any findings. No single stream of data will provide a perfect picture of a dynamic system in operation. Instead, a balanced combination of measures is essential.

Question 23

Zeitgebers:

Answer 23

Biological rhythms influenced by external, or exogenous, cues (from the German: zeit, time; gebers, givers). These cues range from the alternation of light and dark, to social behaviours including time of sleeping and diet. On the other hand, when people are completely isolated from zeitgebers for several days, biological rhythms can still be detected. It would thus appear that the rhythms are also controlled by an internal, or endogenous, ‘clock’.

Question 24

Affordances:

Answer 24

Affordances are an object’s properties that show the possible actions users can take with it, thereby suggesting how they may interact with that object.
eg. A ledge at a comfortable sitting height is likely to be sat on at some point because it AFFORDS the opportunity to the passers by. It looks like a convenient seat therefore it will get used as one. A flat metal cover between knee and waist height over a heater in a lobby will probably therefore end up bent and broken from repeatedly taking people’s weight.
The strength of the affordance will be moderated by:
The context - Something affording ‘support for bags’ is more likely to be recognised and used as such if it’s in a position where you would expect and want to see such a thing - for example near a reception counter where the visitor would be actively searching for an object with these very characteristics.
The culture - Most of us will have experience of reading the affordances of an environment differently to the locals when in an unfamiliar culture and behaving quite inappropriately as a result.
The physical characteristics of the people concerned - such as their dimensions and capabilities. A high ledge does not afford seating to people with short legs. 


Question 25

Cognitive ergonomics:

Answer 25

concerned with mental processes, such as perception, memory, reasoning, and motor response, as they affect interactions among humans and other elements of a system.
Eg. One approach to the study of mental processes is to use the analogy of an information processing system such as a telecommunications system or computer. The usual procedure is to conceptualise mental processes as a sequence of information processing stages. It is assumed that, at each stage, data is processed, and a fixed amount of time is used up. Models of this type have proven to be useful for examining potential limitations in performance, although it must be noted that an orderly sequence of distinct stages doesn’t always match reality.

Question 26

Noise annoyance:

Answer 26

Annoyance during thinking and communication tasks can arise at levels well below 80 dB(A). An excess of noise will prove annoying even though the limit for damage to hearing has not yet been reached. It is mainly noise produced by others, unexpected noise and high frequency noise that cause annoyance. The following table offers suggested maximum noise levels to reduce annoyance for a selection of tasks (adapted from Grandjean, 1988).

Question 27

Percentiles: (often abbreviated to ‘%iles’)

Answer 27

are used in anthropometry to give an indication of the variability of a measure. Percentiles represent percentages of a sample with a measure of value x or less.
Eg. Supposing we had sampled the stature (height) of a group of women between the ages of 30 and 50 years old. Our data could have shown that 95% of the sample were 176.2 cm or shorter: 176.2 cm is the 95th percentile.

Question 28

95th percentile:

Answer 28

5% of the population fall in the 95th%ile. 5% fall in the 5th%ile and the rest are in the other 90% with a mean somewhere around the middle. In the ergonomics literature, it is generally recommended that the 5th and 95th %iles, rather than the 50th %ile, should determine workspace dimensions.
Eg. The maximum height of frequently-used shelves or hand controls should be based on the upward reach of a 5th %ile female. It could be argued that if the shelf or control is within reach of a smaller person then average people and taller people will be accommodated as well. This principle (of the ‘limiting factor’) can be used particularly effectively to design for variations in strength capacities. If an elderly person with limited grip strength is able to operate a control then most other people will have few difficulties. This principle is known as Inclusive Design within architecture.

Question 29

Subjective measurement:

Answer 29

any method that draws its data from the psychological contents of people’s heads.” (Wilson & Corlett, 2005, p. 85).
The opinions of the people within a system are essential sources of information. In effect, you rely on the system stakeholders to come to some sort of conclusion about the system and its behaviour, then access that conclusion as a measurement of the system.
Eg. Interviewing workers.

Question 30

Redundancy (as a principle in design):

Answer 30

We can increase our ability to make absolute judgments by introducing redundant dimensions, redundancy is a built in back up in a system. In a cognitive context, redundancy might be achieved by using a second ‘code’ to reinforce the first and increase the probability of an accurate identification, e.g. if we have a stimulus that comes in 6 sizes we could use an additional dimension, such as colour, to uniquely identify each of the sizes. Size one could be green, size two could be red and so on.

Question 31

Dynamic work:

Answer 31

involves rhythmical changes in the length of a muscle as it alternately contracts and relaxes. Hence, when there is sufficient bodily movement, dynamic work is being performed.
- No posture or movement should be maintained for a long period of time. Prolonged postures and repetitive movements are tiring, and in the long run can lead to injuries to muscles and joints. Dynamic movements ideally should remain within appropriate ranges to reduce the risk of causing injuries.

Question 32

Endogenous clock:

Answer 32

rhythms are also controlled by an internal, or endogenous, ‘clock’. In the absence of zeitgebers, the ‘free- running’ rhythms, which are controlled by the internal clock, tend to have cycles of about 25 hours. Under influence from zeitgebers these free-running rhythms often become adjusted so that their period is 24 hours, called entrainment, otherwise there would be a continuing mismatch between our internal and external time.

Question 33

Autonomous work groups:

Answer 33

Autonomous work groups are teams or groups of workers who complete a whole process and may have some control over how that is done.
Eg. This form of organization can contribute to shorter production times, higher productivity, higher quality, more innovations, higher flexibility, improvement of the quality of work and better labour relations.
(The degree to which the job provides substantial freedom, independence and discretion to the individual in scheduling the work and in determining the procedures to be used in carrying it out. )

Question 34

Literature review:

Answer 34

A comprehensive literature search, and a review of the relevant literature (and other documents such as industry reports).
Eg. Uncovers relevant information from the industry and from refereed work carried out internationally. This information contributes to making a thorough analysis of the workplace and workers involved and can provide ideas for interventions.

Question 35

Semi-structured interview:

Answer 35

A semi-structured interview is a qualitative method of inquiry that combines a pre-determined set of open questions (questions that prompt discussion) with the opportunity for the interviewer to explore particular themes or responses further.
A semi-structured interview does not limit respondents to a set of pre-determined answers (unlike a structured questionnaire).
Eg. Semi-structured interviews are used to understand how interventions work and how they could be improved. It also allows respondents to discuss and raise issues that you may not have considered

Question 36

Circadian rhythms:

Answer 36

A large number of biological rhythms have a period that is close to 24 hours.
Eg. Shift work can affect, and be affected by, circadian rhythms. Circadian rhythms can make adjusting to different sleeping patterns difficult.

Question 37

Aerobic metabolism:

Answer 37

The process of energy generation by oxidation of glucose using the oxygen pathway. The ability to work aerobically is determined by oxygen uptake, and work demands – it occurs when there is sufficient oxygen present to fully break down glucose or glycogen into phosphates, carbon dioxide and water.
Eg. Reduced oxygen environments or confined spaces might inhibit adequate oxygen intake when performing aerobic activities. - Working at altitude would impact on aerobic metabolism.