Bodyspace

Anthropometry, Ergonomics and the Design of Work, Third Edition

Stephen Pheasant, Christine M. Haslegrave

• Editorial: CRC Press
• Año: 2018
• ISBN:
  9781315360560
• Edición: 3
• Categoría: Technologie et ingénierie
• Categoría: Santé et sécurité au travail

In the 20 years since the publication of the first edition of Bodyspace the knowledge base upon which ergonomics rests has increased significantly. The need for an authoritative, contemporary and, above all, usable reference is therefore great. This third edition maintains the same content and structure as previous editions, but updates the material and references to reflect recent developments in the field. The book has been substantially revised to include new research and anthropometric surveys, the latest techniques, and changes in legislation that have taken place in recent years.

New coverage in the third edition:

• Guidance on design strategies and practical advice on conducting trials
• Overview of recent advances in simulation and digital human modes
• Dynamic seating

· Recent work on hand/handle interface

• Computer input devices

· Laptop computer use and children's use of computers

· Design for an aging population and accessibility for people with disabilities

· New approaches to risk management and new assessment tools, legislation, and standards

As the previous two editions have shown, Bodyspace is an example of the unusual: a text that is a favorite among academics and practitioners. Losing none of the features that made previous editions so popular, the author skillfully integrates new knowledge into the existing text without sacrificing the easily accessible style that makes this book unique. More than just a reference text, this authoritative book clearly delineates the field of ergonomics.

Part I

Ergonomics, Design and Anthropometry

1 Introduction to Ergonomic Design

1.1 INTRODUCTION

Several similar contests with the petty tyrants and marauders of the country followed, in all of which Theseus was victorious. One of these was called Procrustes or the stretcher. He had an iron bedstead on which he used to tie all travellers who fell into his hands. If they were shorter than the bed he stretched their limbs to make them fit; if they were longer than the bed he lopped off a portion. Theseus served him as he had served others.

From The Age of Fable by Thomas Bulfinch (1796–1867)

Prior to her injury, ‘Janice’ worked as a word processor operator for a medium-sized firm of management consultants just outside London. She worked in a typing pool with three other girls. One day, one of the partners in the firm needed to get a lot of information entered onto a database in a hurry — and it occurred to him that Janice might work faster if she was in a room on her own where she could not waste time chattering with her friends. So he had a computer terminal set up for her in the firm’s library. It was placed on an antique wooden desk. This was somewhat higher than the standard office desk (antiques often are). It had two plinths and a ‘kneehole drawer’ in the space between them where the user sits. Janice found that however she sat at this desk she could not get into a comfortable working position. She noticed in particular that her wrists were not at their normal angle to the keyboard. It was during the early part of the afternoon that she first began to be aware of a dull ache at the backs of her wrists. This rapidly became worse until she was in considerable discomfort. So she told her boss about it. His response (as it was subsequently alleged) was to say: “Stop whingeing and get on with your work!” So Janice did. As a result, she developed an acute tenosynovitis affecting the extensor tendons of both wrists. Her condition subsequently became chronic, and she was no longer able to type. She lost her job and was forced to take up less well-paid employment as a traffic warden. She took legal action against her employers, who eventually settled ‘on the courtroom steps’ for a substantial sum of money.

What lessons may we learn from the story of ‘Janice’, over and above the more obvious ones concerned with management style and so on? Janice’s injury was the result of a mismatch between the demands of her working task and the capacity of the muscles and tendons of her forearms to meet those demands. To put it another way, the excessive stresses to which these body structures were exposed stemmed from her being forced to adapt to an unsatisfactory working position, which was in turn the result of a mismatch between the dimensions and characteristics of her workstation and those of its user.

Injuries of this sort are common enough (although in Janice’s case the causative factors in question are perhaps unusually clear-cut ones). Indeed in many parts of the world the incidence of such injuries is said to be reaching epidemic proportions. The problem of musculoskeletal injury at work — important as it may be in both economic and human terms — is but one small facet of a much larger class of issues involving the interactions between human beings and the objects and environments they design and use.

To say that we live in an artificial world is something of a truism. Look around you. It is unlikely that you are reading this in a desert wilderness. More probably you are indoors in a furnished room, or in a moving vehicle, or at least in a cultivated garden. It is all too easy to ignore the simple fact that most of the visible and tangible characteristics of the artificial environments in which we spend the greater part of our lives are the consequences of design decisions. By no means are all of the decisions that lead to the creation of these artificial environments made by professional designers. They may be the results of extensive planning or of momentary whims. They represent choices that have been made, which could have been made differently but were by no means inevitable.

All too often, however, the artefacts that we encounter in our human-made environment are like so many Procrustean beds to which we must adapt. Why should this be so? There is a science that deals with such matters. It is called ergonomics.

1.2 WHAT IS ERGONOMICS?

Ergonomics is the science of work: of the people who do it and the ways it is done, of the tools and equipment they use, the places they work in, and the psychosocial aspects of the working situation.

The word ergonomics comes from the Greek ergos, work, and nomos, natural law. The word was coined by the late Professor Hywell Murrell, as a result of a meeting of a working party which was held in Room 1101 of the Admiralty building at Queen Anne’s Mansions on 8 July 1949, at which it was resolved to form a society for ‘the study of human beings in their working environment’. The members of this working party came from backgrounds in engineering, medicine and the human sciences. During the course of the war, which had just ended, they had all been involved with research of one sort or another into the efficiency of the fighting man, and they took the view that the sort of research they had been doing could have important applications under peacetime conditions. There did not seem to be a name for what they had been doing, however, so they had to invent one and finally settled on ergonomics.

The word work admits a number of meanings. In a narrow sense it is what we do for a living. Used in this way, the activity in question is defined by the context in which it is performed rather than by its content. Unless we have some special reason for being interested in the socioeconomic aspects of work, however, this usage is arbitrary. Some people play the violin, keep bees or bake cakes to make a living; others do these things solely for pleasure or for some combination of the two. The content of the activity remains the same.

There is a broader sense, however, in which the term work may be applied to almost any planned or purposeful human activity, particularly if it involves a degree of skill or effort of some sort. In defining ergonomics as a science concerned with human work, we will in general be using the word in this latter and broader sense. Having said this, it would also be true that throughout its 50 years of history, the principal focus of the science of ergonomics has tended to be upon work in the occupational sense of the word.

Work involves the use of tools. Ergonomics is concerned with the design of these — and by extension with the design of artifacts and environments for human use in general. If an object is to be used by human beings, it is presumably to be used in the performance of some purposeful task or activity. Such a task may be regarded as work in the broader sense. Thus to define ergonomics as a science concerned with work or as a science concerned with design means much the same thing at the end of the day.

The ergonomic approach to design may be summarised in the principle of usercentred design:

If an object, a system or an environment is intended for human use, then its design should be based upon the physical and mental characteristics of its human users (insomuch as these may be determined by the investigative methods of the empirical sciences).

The object is to achieve the best possible match between the product (object, system or environment) being designed and its users, in the context of the (working) task that is to be performed (Figure 1.1). In other words, ergonomics is the science of fitting the job to the worker and the product to the user.

1.2.1 WHAT CRITERIA DEFINE A SUCCESSFUL MATCH?

The answer to this question will depend upon the circumstances. Criteria that are commonly important in achieving a successful match include the following:

•Functional efficiency (as measured by productivity, task performance, etc.)

•Ease of use

•Comfort

•Health and safety

•Quality of working life

The ergonomic approach is to consider all relevant criteria, not simply to design for one criterion at the expense of others. Fitting the job to the worker involves consideration of health and quality of working life just as much as of productivity, and efficiency and quality of performance are influenced by all three (see Figure 1.1).

FIGURE 1.1User-centred design: the product, the user and the task.

1.2.2 WHAT IF THESE CRITERIA PROVE INCOMPATIBLE?

Ergonomists often argue that this problem is not as big as it seems. There is some truth in this. There are without doubt circumstances in which ergonomic improvements introduced in the interests of health and safety have a positive pay-off in terms of productivity — and vice versa. Likewise, the product that is easy to use will probably, for that very reason, be both safe and efficient in its operation. It is the difficult-to-use products that are, in general, unsafe and inefficient. It would be naïve to pretend, however, that these sorts of basic criteria that we have invoked to define a good fit are never in conflict, and the deeper we fish in these waters, the more difficult the problem becomes.

The celebrated American product liability case of Grimshaw v. Ford Motor Company in 1981 (Jones, 1986) is illustrative — notwithstanding that it does not deal with ergonomic issues as such. Briefly, the facts were these. The defendants discovered a fault in the design of the petrol tank of one of their models, which meant that it was likely to explode in rear-end collisions. On the basis of certain alleged cost-benefit analyses, they decided that it would be cheaper in the long run to pay damages for the fatalities and injuries that resulted than to redesign the car and opted to take no further action. Outraged by this cynical view of the economic value of human life and limb, an American jury awarded punitive damages of $125 million against the defendants — much greater than any economic benefits that might have accrued to the defendants from failing to take proper steps to contain the hazard. Regrettably perhaps, this was reduced upon appeal to $3.5 million.

This is a somewhat gross example. Cost-benefit trade-offs with implications for health and safety are a fact of everyday industrial life (as any personal injury lawyer will tell you). The fragmented and repetitive short-cycle time tasks of industrial assembly remain an efficient enough way of producing many of the manufactured goods demanded by the consumer economy, but does this production process not have hidden costs? The physical injuries that result are easy enough to recognise, and we could in principle (if we chose) compute the costs of such injuries and incorporate them into some ov...