Week three - five

Question 1

Autonomous work groups

Answer 1

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. Autonomous work groups are teams or groups of workers who complete a whole process and may have some control over how that is done.

Question 2

Business case model

Answer 2

The business case model can be defined as the process by which the cost and investment (resources, time etc) are documented, measured and evaluated.

Question 3

Division of labour

Answer 3

Division of labour refers to the assignment of different parts of a manufacturing process or task to different people in order to improve efficiency. Smith observed that such gains were mainly due to three factors. Firstly, by repeating the same task over and over again body movements become more or less automatic and high speeds can be achieved. Secondly, with workers performing only a limited number of tasks, the need to move about the workplace to collect tools or materials is minimised, leading to time savings. Finally, the development of tools and machinery to help workers perform their specialised jobs is more feasible than in situations where workers are assigned a variety of tasks.

Question 4

Job enlargement

Answer 4

is usually achieved by extending the work cycle. In practice, this might mean extending a 3-minute work cycle to 10 minutes by getting operators to do a series of linked tasks rather than just one task. Alternatively, additional tasks could be incorporated into the work cycle by requiring workers to perform tasks previously performed by service departments. For example, the packing workers in the above example could be required to clean their own work area, do simple maintenance work, or get their work supplies from the stores.

Question 5

Job enrichment

Answer 5

Job enrichment differs from job enlargement in that it involves assigning individuals responsibility over some area of work. For example, 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 6

Job rotation

Answer 6

Rotation can either be formal in that it is prescribed by management or it can be an informal arrangement amongst a group of workers. However, job rotation is likely to be of most value when formally and carefully implemented. One example of rotation would be 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 whereby an operator was rotated 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 7

Job satisfaction

Answer 7

is a measure of workers’ contentedness with their job, whether or not they like the job or individual aspects or facets of jobs, such as the nature of work or supervision.
Job satisfaction can improve employee retention and workplace culture by creating a space employees feel comfortable and supported in.

Question 8

Safety culture

Answer 8

defined as the collection of the beliefs, perceptions and values that employees share in relation to the safety and risks in the organisation or workplace. The safety culture drives employee behaviours and ultimately impacts on efficiency and productivity of the organisation.

Question 9

Aerobic metabolism:

Answer 9

Aerobic metabolism is the process by which energy is generated by oxidation of glucose using 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.

Question 10

Anaerobic metabolism;

Answer 10

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 11

Basal metabolism;

Answer 11

Even to stay alive in a state of ‘bed rest’ we need to expend a certain amount of energy. This is referred to as basal metabolism – i.e. the daily amount of energy the body requires if at rest in a temperate environment. In addition to our basal requirements, we use energy when we engage in work and leisure activities. Hence, we can partition our total energy expenditure in three ways: basal metabolism, work joules and leisure joules.

Question 12

Biomechanical models;

Answer 12

The influence of posture on joint pressure and muscle force can be explained using biomechanical models. These refer to the application of mechanical principles to the human body. Models will consider the human body and interactions with the workplace, to indicate loading on structures in the body (eg torque, force). These mathematical models can get quite complex and the following section provides only a limited appreciation of some of the fundamentals of this technique. Mechanical concepts of weight, centre of gravity and torque are important.

Question 13

Centre of gravity;

Answer 13

The centre of gravity is that point at the exact centre of an object’s mass. In the case of a solid square block in which the mass is symmetrically distributed the centre of gravity is at the geometric centre of the object. However, if the distribution of mass is asymmetrical, as is the case for the limbs of the body, the centre of gravity will be nearer to the larger, heavier, end.
The centre of gravity of the human body is dependent of the centres of gravity of each body part – to maintain a stable posture, the combined centres of gravity need to fall within the area of contact between the body and supporting surface – ie the base of support.

Question 14

Dynamic work;

Answer 14

Dynamic work 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.

Question 15

Energy expenditure;

Answer 15

Energy expenditure described the amount of energy (or calories) that a person needs to carry out a physical function such as breathing, circulating blood, digesting food, or physical movement; total daily energy expenditure (TDEE) is the total number of calories used each day.

Question 16

Fatigue;

Answer 16

Fatigue is generally considered to be a decline in mental and/or physical performance that results from physical prolonged exertion, sleep loss and/or disruption of the internal clock. Workers are more easily fatigued if their work is machine-paced, complex or monotonous. Fatigue is also associated with the issues that arise from excessive working time or poorly designed shift patterns.

Question 17

Heart rate;

Answer 17

The speed the heart beats at.

Question 18

Ligaments and tendons;

Answer 18

Connective tissues connecting bone to bone - Ligaments, or muscle to bone - tendons.

Question 19

Lordosis;

Answer 19

The natural curvature of the spine.

Question 20

Manual (materials) handling;

Answer 20

Manual handling refers to activities whereby the body is used to exert force to handle, support or restrain any object, including not only lifting and carrying but also repetitive tasks.

Question 21

Maximal oxygen uptake;

Answer 21

Maximal oxygen uptake refers to the maximum rate of oxygen consumption measured during incremental exercise (exercise of increasing intensity).

Question 22

Maximum voluntary contraction;

MVC;

Answer 22

Strength data that is measured and presented in ergonomics handbooks almost exclusively relate to the combined effect of groups of muscles associated with certain actions such as pulling, pushing or lifting. In addition, the strength data that are presented are often maximum voluntary contractions. This type of contraction (often referred to as the MVC) is defined as the maximum static contraction that can be maintained voluntarily for four to six seconds. The MVC is useful because we can express muscle activity associated with work tasks as a percentage, or fraction, of MVC. For example, the muscular contraction associated with holding a forward inclined head posture while typing might be around 20 percent of the maximum for the muscle group involved. This would be expressed either as 20% MVC or 0.2 MVC.

Question 23

Oxygen uptake:

Answer 23

Oxygen uptake is the rate at which oxygen is able to be used during activity, and is determined by metabolic demands or loading. We can use oxygen uptake as an indirect measure of work joules, because it has been established that the combustion of one litre of oxygen will produce 20 kJ of energy. Thus, if we know the oxygen uptake, in litres of oxygen per minute (in shorthand: l02/min), we can multiply this by a factor of 20 to obtain the rate of energy expenditure in kJ/min.

Question 24

Postural fixity;

Answer 24

An inability to achieve postural variety - referred to as postural fixity

Question 25

Proprioceptors;

Answer 25

Proprioceptors are body sensors (sensory receptors) of movement and position, joint angle, muscle tension, muscle length. These receptors are stimulated by muscular activity, and tell us (without the need to look) where our limbs are at any given moment. This proprioceptive sense helps us coordinate our movements.

Question 26

Static work:

Answer 26

This occurs when a muscle contracts but does not vary in length – i.e. sustained muscle activity without a repetitive cycle of contraction and relaxation. The action of holding your arm out horizontally at shoulder level is a good example. 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 27

95th percentile;

Answer 27

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

Question 28

Anthropometric dimensions;

Answer 28

An anthropometric dimension such as Eye Height Sitting is made up of three terms. The locator is that body landmark or point whose distance from some other point is being measured (e.g. Eye), whereas the direction of the dimension is the orientator (e.g. Height). The positioner identifies the body position which the subject adopts for the measurement (e.g. Sitting). The measurements of a specific dimension.

Question 29

Anthropometry:

Answer 29

Anthropometry is the branch of human sciences that refers to the measurement of the human body. It involves the systematic measurement of the physical properties of the human body, primarily dimensional descriptors of body size, shape, strength and capacity.

Question 30

Fitting trial;

Answer 30

Fitting trials involve the use of live subjects as manikins (Singleton, 1972) to test a full- scale model or mock-up of a workspace or product. A sample of subjects can be used to make judgements about particular workstations or product dimensions. Anthropometric data can provide a guide as to who to select as subjects for the trial. For example, if you are interested in seeing how short New Zealand women will cope with a workspace, you may wish to include women in your sample who are close to 5th percentile in stature. From your knowledge of the data tables above, you would know to select women who were around 153-155 cm tall. Although fitting trials are most often used for observing the behaviour of users and receiving their subjective comments, they can also be used to establish the percentage (or interpercentile range) of potential end-users that will be accommodated by the proposed design.

Question 31

Functional anthropometry;

Answer 31

Functional dimensions are measured when the body adopts non-standard postures. Generally, these non-standard postures are more natural. Examples of functional dimensions are reaches and clearances. Data relating to strengths and joint range of movement are sometimes included in this category. 
Newtonian anthropometric data are necessary inputs for the study of Biomechanics.

Question 32

Mean;

Answer 32

The mean is an indication of the central tendency of a sample (and, by inference, the population). It is obtained by calculating the arithmetic average (the sum of all values divided by the sample size).

Question 33

Normal distribution:

Answer 33

As with many other biological characteristics, anthropometric dimensions are often characterised by a normal distribution as represented by a bell-shaped curve. This situation is fortunate in that we are able, in anthropometry, to apply statistical techniques, such as standard deviations and percentiles, which are based upon the assumption that population distributions of interest are ‘normal’. In practice, deviations from normality can occur. For example, when we combine two normal distributions (e.g. males and females) we either get a platykurtic (flat-topped) curve or a bimodal (double-peaked) curve. According to Pheasant (1986) the errors that might result from applying normal statistics to these data distributions will be negligible.

Question 34

Percentile;

Answer 34

Percentiles (often abbreviated to ‘%iles’) 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. This is best explained using an example. 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.
If we calculated the 5th percentile, we could describe 5% of the group as shorter than this value; and at the 95th percentile, we can describe 5% of the group as taller. The 50th percentile would indicate 50% are shorter and 50% taller.

Question 35

Population;

Answer 35

a finite or infinite collection of items under consideration.

Question 36

Power grip;

Answer 36

In a power grip the fingers and thumb are used to clamp the object against the palm, as in gripping a hammer.

Question 37

Precision grip;

Answer 37

in a precision grip the object is manipulated between the pads of the fingers and thumb, as in holding a pair of tweezers.

Question 38

Sample:

Answer 38

Consider that we have been asked to advise on the design of furniture for secondary schoolchildren. Rather than measuring each student (thousands of them!) we would select a sample for measurement purposes. From this sample we could then infer or predict characteristics about the population from which the sample was drawn.

Question 39

Standard deviation;

Answer 39

The standard deviation is an indicator of the variability that exists in the population concerned. The standard deviation influences the shape of the normal distribution: if it is wide and flat the standard deviation is relatively high, if it is narrow and tall the standard deviation is relatively low.

Question 40

Ulnar deviation;

Answer 40

(right hand) Fingers go this —–> way

Question 41

Radial deviation;

Answer 41

(right hand) Thumb goes this

Question 42

Usability;

Answer 42

Consideration of user, task, equipment and environment with respect to the design of a workplace, system or product.

Question 43

Working height;

Answer 43

The working height is generally the height at which the hands are positioned.

Question 44

Workspace envelope;

Answer 44

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 envelop 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 45

Work Related Upper Limb Disorders: WRULD

Answer 45

This term describes a diverse range of conditions related to overuse of tissues, which are also known as:
OOS (Occupational Overuse Syndrome)
RSI (Repetitive Strain Injuries)
Musculoskeletal disorders (MSD) of the upper extremities
Upper limb MSD

Occupational groups exposed to these conditions are those where risk factors include: 
Force 
Psychosocial factors – especially high job stress and high job demands  
Repetition and force (combined) 
Repetition 
Static loading 
Vibration 
Manual handling