Origins

Standardization in the field of ergonomics has a relatively short history. It started in the beginning of the 1970s when the first committees were founded on the national level (e.g., in Germany within the standardization institute DIN), and it continued on an international level after the foundation of the ISO (International Organization for Standardization) TC (Technical Committee) 159 “Ergonomics”, in 1975. In the meantime ergonomics standardization takes place on regional levels as well, for example, on the European level within the CEN (Commission européenne de normalisation), which established its TC 122 “Ergonomics” in 1987. The existence of the latter committee underscores the fact that one of the important reasons for establishing committees for the standardization of ergonomics knowledge and principles can be found in legal (and quasi-legal) regulations, especially with respect to safety and health, which require the application of ergonomics principles and findings in the design of products and work systems. National laws requiring the application of well-established ergonomics findings were the reason for the establishment of the German ergonomics committee in 1970, and European Directives, especially the Machinery Directive (relating to safety standards), were responsible for establishing an ergonomics committee on the European level. Since legal regulations usually are not, cannot and should not be very specific, the task of specifying which ergonomics principles and findings should be applied was given to or taken up by ergonomics standardization committees. Especially on the European level, it can be recognized that ergonomics standardization can contribute to the task of providing for broad and comparable conditions of machinery safety, thus removing barriers to the free trade of machinery within the continent itself.

Perspectives

Ergonomics standardization thus started with a strong protective, although preventive, perspective, with ergonomics standards being developed with the aim of protecting workers against adverse effects at different levels of health protection. Ergonomics standards were thus prepared with the following intentions in view:

• to ensure that assigned tasks do not exceed the limits of the performance capacities of the worker

• to prevent injury or any detrimental effects to the health of the worker whether permanent or transient, either in the short or in the long run, even if the tasks in question can be performed, if only for a short time, without negative effects

• to provide that tasks and working conditions will not lead to impairments, even if recuperation is possible with time.

International standardization, which was not so closely coupled to legislation, on the other hand, always also tried to open a perspective in the direction of producing standards which would go beyond the prevention of and protection against adverse effects (e.g., by specifying minimal/maximal values) and instead proactively provide for optimal working conditions to promote the well-being and personal development of the worker, as well as the effectiveness, efficiency, reliability and productivity of the work system.

This is a point where it becomes evident that ergonomics, and especially ergonomics standardization, has very distinct social and political dimensions. Whereas the protective approach with respect to safety and health is generally accepted and agreed upon among the parties involved (employers, unions, administration and ergonomics experts) for all levels of standardization, the proactive approach is not equally accepted by all parties in the same way. This might be due to the fact that, especially where legislation requires the application of ergonomics principles (and thus either explicitly or implicitly the application of ergonomics standards), some parties feel that such standards might limit their freedom of action or negotiation. Since international standards are less compelling (transferring them into the body of national standards is at the discretion of the national standardization committees) the proactive approach has been developed furthest at the international level of ergonomics standardization.

The fact that certain regulations would indeed restrict the discretion of those to whom they applied served to discourage standardization in certain areas, for example in connection with the European Directives under Article 118a of the Single European Act, relating to safety and health in the use and operation of machinery at the workplace, and in the design of work systems and workplace design. On the other hand, under the Directives issued under Article 100a, relating to safety and health in the design of machinery with regard to the free trade of this machinery within the European Union (EU), European ergonomics standardization is mandated by the European Commission.

From an ergonomics point of view, however, it is difficult to understand why ergonomics in the design of machinery should be different from that in the use and operation of machinery within a work system. It is thus to be hoped that the distinction will be given up in the future, since it seems to be more detrimental than beneficial to the development of a consistent body of ergonomics standards.

Types of Ergonomics Standards

The first international ergonomics standard to have been developed (based on a German DIN national standard) is ISO 6385, “Ergonomic principles in the design of work systems”, published in 1981. It is the basic standard of the ergonomics standards series and set the stage for the standards which followed by defining the basic concepts and stating the general principles of the ergonomic design of work systems, including tasks, tools, machinery, workstations, work space, work environment and work organization. This international standard, which is now undergoing revision, is a guideline standard, and as such provides guidelines to be followed. It does not, however, provide technical or physical specifications which have to be met. These can be found in a different type of standards, that is, specification standards, for example, those on anthropometry or thermal conditions. Both types of standards fulfil different functions. While guideline standards intend to show their users “what to do and how to do it” and indicate those principles that must or should be observed, for example, with respect to mental workload, specification standards provide users with detailed information about safety distances or measurement procedures, for example, that have to be met and where compliance with these prescriptions can be tested by specified procedures. This is not always possible with guideline standards, although despite their relative lack of specificity it can usually be demonstrated when and where guidelines have been violated. A subset of specification standards are “database” standards, which provide the user with relevant ergonomics data, for example, body dimensions.

CEN standards are classified as A-, B- and C-type standards, depending on their scope and field of application. A-type standards are general, basic standards which apply to all kinds of applications, B-type standards are specific for an area of application (which means that most of the ergonomics standards within the CEN will be of this type), and C-type standards are specific for a certain kind of machinery, for example, hand-held drilling machines.

Standardization Committees

Ergonomics standards, like other standards, are produced in the appropriate technical committees (TCs), their subcommittees (SCs) or working groups (WGs). For the ISO this is TC 159, for CEN it is TC 122, and on the national level, the respective national committees. Besides the ergonomics committees, ergonomics is also dealt with in TCs working on machine safety (e.g., CEN TC 114 and ISO TC 199) with which liaison and close cooperation is maintained. Liaisons are also established with other committees for which ergonomics might be of relevance. Responsibility for ergonomics standards, however, is reserved to the ergonomics committees themselves.

A number of other organizations are engaged in the production of ergonomics standards, such as the IEC (International Electrotechnical Commission); CENELEC, or the respective national committees in the electrotechnical field; CCITT (Comité consultative international des organisations téléphoniques et télégraphiques) or ETSI (European Telecommunication Standards Institute) in the field of telecommunications; ECMA (European Computer Manufacturers Association) in the field of computer systems; and CAMAC (Computer Assisted Measurement and Control Association) in the field of new technologies in manufacturing, to name only a few. With some of these the ergonomics committees do have liaisons in order to avoid duplication of work or inconsistent specifications; with some organizations (e.g., the IEC) even joint technical committees are established for cooperation in areas of mutual interest. With other committees, however, there is no coordination or cooperation at all. The main purpose of these committees is to produce (ergonomics) standards that are specific to their field of activity. Since the number of such organizations at the different levels is rather large, it becomes quite complicated (if not impossible) to carry out a complete overview of ergonomics standardization. The present review will therefore be restricted to ergonomics standardization in the international and European ergonomics committees.

Structure of Standardization Committees

Ergonomics standardization committees are quite similar to one another in structure. Usually one TC within a standardization organization is responsible for ergonomics. This committee (e.g., ISO TC 159) mainly has to do with decisions about what should be standardized (e.g., work items) and how to organize and coordinate the standardization within the committee, but usually no standards are prepared at this level. Below the TC level are other committees. For example, the ISO has subcommittees (SCs), which are responsible for a defined field of standardization: SC 1 for general ergonomic guiding principles, SC 3 for anthropometry and biomechanics, SC 4 for human-system interaction and SC 5 for the physical work environment. CEN TC 122 has working groups (WGs) below the TC level which are so constituted as to deal with specified fields within ergonomics standardization. SCs within ISO TC 159 operate as steering committees for their field of responsibility and do the first voting, but usually they do not also prepare standards. This is done in their WGs, which are composed of experts nominated by their national committees, whereas SC and TC meetings are attended by national delegations representing national points of view. Within the CEN, duties are not sharply distinguished at the WG level; WGs operate both as steering and production committees, although a good deal of work is accomplished in ad hoc groups, which are composed of members of the WG (nominated by their national committees) and established to prepare the drafts for a standard. WGs within an ISO SC are established to do the practical standardization work, that is, prepare drafts, work on comments, identify needs for standardization, and prepare proposals to the SC and TC, which will then take the appropriate decisions or actions.

Preparation of Ergonomics Standards

The preparation of ergonomics standards has changed quite markedly within the last years in view of the stronger emphasis now being placed on European and other international developments. In the beginning, national standards, which had been prepared by experts from one country in their national committee and agreed upon by the interested parties among the general public of that country in a specified voting procedure, were transferred as input to the responsible SC and WG of ISO TC 159, after a formal vote had been taken at the TC level that such an international standard should be prepared. The working group, composed of ergonomics experts (and experts from politically interested parties) from all participating member bodies (i.e., the national standardization organizations) of TC 159 who were willing to cooperate in this work project, would then work on any inputs and prepare a working draft (WD). After this draft proposal is agreed upon in the WG, it becomes a committee draft (CD), which is distributed to the member bodies of the SC for approval and comments. If the draft receives substantial support from the SC member bodies (i.e., if at least two-thirds vote in favour) and after comments by the national committees have been incorporated by the WG in the improved version, a Draft International Standard (DIS) is submitted for voting to all members of TC 159. If substantial support, at this step from the member bodies of the TC, is achieved (and perhaps after incorporating editorial changes), this version will then be published as an International Standard (IS) by the ISO. Voting of the member bodies at the TC and SC level is based on voting at the national level, and comments can be supplied through the member bodies by experts or interested parties in each country. The procedure is roughly equivalent in CEN TC 122, with the exception that there are no SCs below the TC level and that voting takes part with weighted votes (according to the size of the country) whereas within the ISO the rule is one country, one vote. If a draft fails at any step, and unless the WG decides that an agreeable revision cannot be achieved, it has to be revised and then has to pass through the voting procedure again.

International standards are then transferred into national standards if the national committees vote accordingly. By contrast, European Standards (ENs) have to be transferred into national standards by the CEN members and conflicting national standards have to be withdrawn. That means that harmonized ENs will be effective in all CEN countries (and, due to their influence on trade, will be relevant to manufacturers in all other countries who intend to sell goods to a customer in a CEN country).

ISO-CEN Cooperation

In order to avoid conflicting standards and duplication of work and to allow non-CEN members to take part in developments in the CEN, a cooperative agreement between the ISO and the CEN has been achieved (the so-called Vienna Agreement) which regulates the formalities and provides for a so-called parallel voting procedure, which allows the same drafts to be voted upon in the CEN and the ISO in parallel, if the responsible committees agree to do so. Among the ergonomics committees the tendency is quite clear: avoid duplication of work (manpower and financial resources are too limited), avoid conflicting specifications, and try to achieve a consistent body of ergonomics standards based on a division of labour. Whereas CEN TC 122 is bound by the decisions of the EU administration and gets mandated work items to stipulate the specifications of European directives, ISO TC 159 is free to standardize whatever it thinks necessary or appropriate in the field of ergonomics. This has led to shifts in the emphasis of both committees, with the CEN concentrating on machinery and safety-related topics and the ISO concentrating on areas where broader market interests than Europe are concerned (e.g., work with VDUs and control-room design for process and related industries); on areas where the operation of machinery is concerned, as in work system design; and on such areas as work environment and work organization as well. The intention, however, is to transfer work results from the CEN to the ISO, and vice versa, in order to build up a body of consistent ergonomics standards which in fact are effective all over the world.

The formal procedure of producing standards is still the same today. But since the emphasis has shifted more and more to the international or the European level, more and more activities are being transferred to these committees. Drafts are now usually worked out directly in these committees and are no longer based on existing national standards. After the decision has been made that a standard should be developed, work directly starts at one of these supranational levels, based on whatever input there may be available, sometimes starting from zero. This changes the role of the national ergonomics committees quite dramatically. While heretofore they formally developed their own national standards according to their national rules, they now have the task of observing and influencing standardization on the supranational levels—via the experts who work out the standards or via comments made at the different steps of voting (within the CEN, a national standardization project will be halted if a comparable project is being simultaneously worked on at the CEN level). This makes the task still more complicated, since this influence can only be exerted indirectly and since the preparation of ergonomics standards is not just a matter of pure science but a matter of bargaining, consensus and agreement (not least due to the political implications which the standard might have). This, of course, is one of the reasons why the process of producing an international or European ergonomics standard usually takes several years and why ergonomics standards cannot reflect the latest state of the art in ergonomics. International ergonomics standards thus have to be examined every five years, and, if necessary, undergo revision.

Fields of Ergonomics Standardization

International ergonomics standardization started with guidelines on the general principles of ergonomics in the design of work systems; they were laid down in ISO 6385, which is now under revision in order to incorporate new developments. The CEN has produced a similar basic standard (EN 614, Part 1, 1994)—this is oriented more to machinery and safety—and is preparing a standard with guidelines on task design as a second part of this basic standard. The CEN thus emphasizes the importance of operator tasks in the design of machinery or work systems, for which appropriate tools or machinery have to be designed.

Another area where concepts and guidelines have been laid down in standards is the field of mental workload. ISO 10075, Part 1, defines terms and concepts (e.g., fatigue, monotony, reduced vigilance), and Part 2 (at the stage of a DIS in the latter half of the 1990s) provides guidelines for the design of work systems with respect to mental workload in order to avoid impairments.

SC 3 of ISO TC 159 and WG 1 of CEN TC 122 produce standards on anthropometry and biomechanics, covering, among other topics, methods of anthropometric measurements, body dimensions, safety distances and access dimensions, the evaluation of working postures and the design of workplaces in relation to machinery, recommended limits of physical strength and problems of manual handling.

SC 4 of ISO 159 shows how technological and social changes affect ergonomics standardization and the programme of such a subcommittee. SC 4 started as “Signals and Controls” by standardizing principles for displaying information and designing control actuators, with one of its work items being the visual display unit (VDU), used for office tasks. It soon became apparent, however, that standardizing the ergonomics of VDUs would not be sufficient, and that standardization “around” this workstation—in the sense of a work system—was required, covering areas such as hardware (e.g., the VDU itself, including displays, keyboards, non-keyboard input devices, workstations), work environment (e.g., lighting), work organization (e.g., task requirements), and software (e.g., dialogue principles, menu and direct manipulation dialogues). This led to a multipart standard (ISO 9241) covering “ergonomic requirements for office work with VDUs” with at the moment 17 parts, 3 of which have reached the status of an IS already. This standard will be transferred to the CEN (as EN 29241) which will specify requirements for the VDU directive (90/270 EEC) of the EU—although this is a directive under article 118a of the Single European Act. This series of standards provides guidelines as well as specifications, depending on the subject of the given part of the standard, and introduces a new concept of standardization, the user performance approach, which might help to solve some of the problems in ergonomics standardization. It is described more fully in the chapter Visual Display Units .

The user performance approach is based on the idea that the aim of standardization is to prevent impairment and to provide for optimal working conditions for the operator, but not to establish technical specification per se. Specification is thus regarded only as a means to the end of unimpaired, optimal user performance. The important thing is to achieve this unimpaired performance of the operator, regardless of whether a certain physical specification is met. This requires that the unimpaired operator performance which has to be achieved, for example, reading performance on a VDU, must be specified in the first place, and second, that technical specifications be developed which will enable the desired performance to be achieved, based on the available evidence. The manufacturer is then free to follow these technical specifications, which will ensure that the product complies with the ergonomics requirements. Or he may demonstrate, by comparison with a product that is known to fulfil the requirements (either by compliance with the technical specifications of the standard or by proven performance), that with the new product the performance requirements are equally or better fulfilled than with the reference product, with or without compliance to the technical specifications of the standard. A test procedure which has to be followed for demonstrating conformance with the user performance requirements of the standard is specified in the standard.

This approach helps to overcome two problems. Standards, by virtue of their specifications, which are based on the state of the art (and technology) at the time of preparation of the standard, can restrict new developments. Specifications that are based on a certain technology (e.g., cathode-ray tubes) may be inappropriate for other technologies. Independently of technology, however, the user of a display device (for instance) should be able to read and understand the information displayed effectively and efficiently without any impairments, irrespective of whatever technique may be used. Performance in this case must, however, not be restricted to the pure output (as measured in terms of speed or accuracy) but must include considerations of comfort and effort as well.

The second problem that can be dealt with by this approach is the problem of interactions between conditions. Physical specification usually is unidimensional, leaving other conditions out of consideration. In the case of interactive effects, however, this can be misleading or even wrong. By specifying performance requirements, on the other hand, and leaving the means to achieve these to the manufacturer, any solution that satisfies these performance requirements will be acceptable. Treating specification as a means to an end thus represents a genuine ergonomic perspective.

Another standard with a work system approach is under preparation in SC 4, which relates to the design of control rooms, for instance, for process industries or power stations. A multipart standard (ISO 11064) is expected to be prepared as a result, with the different parts dealing with such aspects of control-room design as layout, operator workstation design, and the design of displays and input devices for process control. Because these work items and the approach taken clearly exceed problems of the design of “displays and controls”, SC 4 has been renamed “Human-System Interaction”.

Environmental problems, especially those relating to thermal conditions and communication in noisy environments, are dealt with in SC 5, where standards have been or are being prepared on measurement methods, methods for the estimation of heat stress, conditions of thermal comfort, metabolic heat production, and on auditory and visual danger signals, speech interference level and the assessment of speech communication.

CEN TC 122 covers roughly the same fields of ergonomics standardization, although with a different emphasis and a different structure of its working groups. It is intended, however, that by a division of labour between the ergonomics committees, and mutual acceptance of work results, a general and usable set of ergonomics standards will be developed.

Back

Work systems encompass such macro level organizational variables as the personnel subsystem, the technological subsystem and the external environment. The analysis of work systems is, therefore, essentially an effort to understand the allocation of functions between the worker and the technical outfit and the division of labour between people in a sociotechnical environment. Such an analysis can assist in making informed decisions to enhance systems safety, efficiency in work, technological development and the mental and physical well-being of workers.

Researchers examine work systems according to divergent approaches (mechanistic, biological, perceptual/motor, motivational) with corresponding individual and organizational outcomes (Campion and Thayer 1985). The selection of methods in work systems analysis is dictated by the specific approaches taken and the particular objective in view, the organizational context, the job and human characteristics, and the technological complexity of the system under study (Drury 1987). Checklists and questionnaires are the common means of assembling databases for organizational planners in prioritizing action plans in areas of personnel selection and placement, performance appraisal, safety and health management, worker-machine design and work design or redesign. Inventory methods of checklists, for example the Position Analysis Questionnaire, or PAQ (McCormick 1979), the Job Components Inventory (Banks and Miller 1984), the Job Diagnostic Survey (Hackman and Oldham 1975), and the Multi-method Job Design Questionnaire (Campion 1988) are the more popular instruments, and are directed to a variety of objectives.

The PAQ has six major divisions, comprising 189 behavioural items required for the assessment of job performance and seven supplementary items related to monetary compensation:

• information input (where and how does one get information on the jobs to perform) (35 items)

• mental process (information processing and decision-making in performing the job) (14 items)

• work output (physical work done, tools and devices used) (50 items)

• interpersonal relationships (36 items)

• work situation and job context (physical/social contexts) (18 items)

• other job characteristics (work schedules, job demands) (36 items).

The Job Components Inventory Mark II contains seven sections. The introductory section deals with the details of the organization, job descriptions and biographical details of the job holder. Other sections are as follows:

• tools and equipment—uses of over 200 tools and equipment (26 items)

• physical and perceptual requirements—strength, coordination, selective attention (23 items)

• mathematical requirements—uses of numbers, trigonometry, practical applications, e.g., work with plans and drawings (127 items)

• communication requirements—the preparation of letters, use of coding systems, interviewing people (19 items)

• decision-making and responsibility—decisions about methods, order of work, standards and related issues (10 items)

• job conditions and perceived job characteristics.

The profile methods have common elements, that is, (1) a comprehensive set of job factors used to select the range of work, (2) a rating scale that permits the evaluation of job demands, and (3) the weighing of job characteristics based on organizational structure and sociotechnical requirements. Les profils des postes, another task profile instrument, developed in the Renault Organization (RNUR 1976), contains a table of entries of variables representing working conditions, and provides respondents with a five-point scale on which they can select the value of a variable that ranges from very satisfactory to very poor by way of registering standardized responses. The variables cover (1) the design of the workstation, (2) the physical environment, (3) the physical load factors, (4) nervous tension, (5) job autonomy, (6) relations, (7) repetitiveness and (8) contents of work.

The AET (Ergonomic Job Analysis) (Rohmert and Landau 1985), was developed based on the stress-strain concept. Each of the 216 items of the AET are coded: one code defines the stressors, indicating whether a work element does or does not qualify as a stressor; other codes define the degree of stress associated with a job; and yet others describe the duration and frequency of stress during the work shift.

The AET consists of three parts:

• Part A. The Man-at-Work system (143 items) includes the work objects, tools and equipment, and work environment constituting the physical, organizational, social and economic conditions of work.

• Part B. The Task analysis (31 items) classified according to both the different kinds of work object, such as material and abstract objects, and worker-related tasks.

• Part C. The Work Demand analysis (42 items) comprises the elements of perception, decision and response/activity. (The AET supplement, H-AET, covers body postures and movements in industrial assembling activities).

Broadly speaking, the checklists adopt one of two approaches, (1) the job-oriented approach (e.g., the AET, Les profils des postes) and (2) the worker-oriented approach (e.g., the PAQ). The task inventories and profiles offer subtle comparison of complex tasks and occupational profiling of jobs and determine the aspects of work which are considered a priori as inevitable factors in improving working conditions. The emphasis of the PAQ is on classifying job families or clusters (Fleishman and Quaintence 1984; Mossholder and Arvey 1984; Carter and Biersner 1987), inferring job component validity and job stress (Jeanneret 1980; Shaw and Riskind 1983). From the medical point of view, both the AET and the profile methods allow comparisons of constraints and aptitudes when required (Wagner 1985). The Nordic questionnaire is an illustrative presentation of ergonomic workplace analysis (Ahonen, Launis and Kuorinka 1989), which covers the following aspects:

• work space

• general physical activity

• lifting activity

• work postures and movements

• accident risk

• job content

• job restrictiveness

• worker’s communication and personal contacts

• decision-making

• repetitiveness of the work

• attentiveness

• lighting conditions

• thermal environment

• noise.

Among the shortcomings of the general-purpose checklist format employed in ergonomic job analysis are the following:

• With some exceptions (e.g., the AET, and the Nordic questionnaire), there is a general lack of ergonomics norms and protocols of evaluation with respect to the different aspects of work and environment.

• There are dissimilarities in the overall construction of the checklists as regards means of determining the characteristics of working conditions, the quotation form, criteria and methods of testing.

• The evaluation of physical workload, work postures and work methods is limited on account of lack of precision in the analysis of work operations, with reference to the scale of relative levels of stress.

• The principal criteria of assessment of the worker’s mental load are the degree of complexity of the task, the attention required by the task and the execution of mental skills. The existing checklists refer less to underuse of abstract thought mechanisms than to overuse of concrete thought mechanisms.

• In most checklists, methods of analysis attach major importance to the job as a position as opposed to the analysis of work, worker-machine compatibility, and so forth. The psycho-sociological determinants, which are fundamentally subjective and contingent, are less emphasized in the ergonomics checklists.

A systematically constructed checklist obliges us to investigate the factors of work conditions which are visible or easy to modify, and permits us to engage in a social dialogue between employers, job holders and others concerned. One should exercise a degree of caution towards the illusion of simplicity and efficiency of the checklists, and towards their quantifying and technical approaches as well. Versatility in a checklist or questionnaire can be achieved by including specific modules to suit specific objectives. Therefore, the choice of variables is very much linked to the purpose for which the work systems are to be analysed and this determines the general approach for construction of a user-friendly checklist.

The suggested “Ergonomics Checklist” may be adopted for various applications. Data collection and computerized processing of the checklist data are relatively straightforward, by responding to the primary and secondary statements (q.v.).

ERGONOMICS CHECKLIST

A broad guideline for a modular-structured work systems checklist is suggested here, covering five major aspects (mechanistic, biological, perceptual/motor, technical and psychosocial). Weighting of the modules varies with the nature of the job(s) to be analysed, the specific features of the country or population under study, organizational priorities and the intended use of the results of the analysis. Respondents mark the “primary statement” as Yes/No. “Yes” answers indicate the apparent absence of a problem, although the advisability of further careful scrutiny should not be ruled out. “No” answers indicate a need for an ergonomics evaluation and improvement. Responses to “secondary statements” are indicated by a single digit on the severity of agreement/disagreement scale illustrated below.

0            Do not know or not applicable

1            Strongly disagree

2            Disagree

3            Neither agree nor disagree

4            Agree

5            Strongly agree

A. Organization, worker and the task    Your answers/ratings

The checklist designer may provide a sample drawing/photograph of work and
workplace under study.

1. Description of organization and functions.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

2. Worker characteristics: A brief account of the work group.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

3. Task description: List activities and materials in use. Give some indication of 
the work hazards.

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

B. Mechanistic aspect    Your answers/ratings

I. Job Specialization

4.Tasks/work patterns are simple and uncomplicated.             Yes/No

If No, rate the following:            (Enter 0-5)

4.1 Job assignment is specific to the operative.        

4.2 Tools and methods of work are specialized to the purpose of the job.  

4.3 Production volume and quality of work.  

4.4 Job holder performs multiple tasks.   

II. Skill Requirement

5. Job requires simple motor act.             Yes/No

If No, rate the following:            (Enter 0-5)

5.1 Job requires knowledge and skilful ability.    

5.2 Job demands training for skill acquisition.     

5.3 Worker makes frequent mistakes at work.    

5.4 Job demands frequent rotation, as directed.   

5.5 Work operation is machine paced/assisted by automation.   

Remarks and suggestions for improvement. Items 4 to 5.5:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

q Analyst’s rating       Worker’s rating q

C. Biological aspect    Your answers/ratings

III. General Physical Activity

6. Physical activity is entirely determined and
regulated by the worker.            Yes/No

If No, rate the following:            (Enter 0-5)

6.1 Worker maintains target-oriented pace.   

6.2 Job implies frequently repeated movements.   

6.3 Cardiorespiratory demand of the job:   

sedentary/light/moderate/heavy/ extremely heavy. 

(What are the heavy work elements?):

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

(Enter 0-5)

6.4 Job demands high muscular strength exertion.   

6.5 Job (operation of handle, steering wheel, pedal brake) is predominantly static work.   

6.6. Job requires fixed working position (sitting or standing).   

IV.  Manual Materials Handling (MMH)

Nature of objects handled: animate/inanimate, size and shape.

_______________________________________________________________

_______________________________________________________________

7. Job requires minimal MMH activity.            Yes/No

If No, specify the work:

7.1 Mode of work:        (circle one)

pull/push/turn/lift/lower/carry

(Specify repetition cycle):

_______________________________________________________________

_______________________________________________________________

7.2 Load weight (kg):        (circle one)

5-10, 10-20, 20-30, 30-40, >>40.

7.3 Subject-load horizontal distance (cm):       (circle one)

<25, 25-40, 40-55, 55-70, >70.

7.4 Subject-load height:       (circle one)

ground, knee, waist, chest, shoulder level.

(Enter 0-5)

7.5 Clothing restricts MMH tasks.   

8. Task situation is free from risk of bodily injury.            Yes/No

If No, rate the following:            (Enter 0-5)        

8.1 Task can be modified to reduce the load to be handled.   

8.2 Materials can be packed in standard sizes.   

8.3 Size/position of handles on objects may be improved.   

8.4 Workers do not adopt safer methods of load handling.   

8.5 Mechanical aids may reduce bodily strains.
List each item if hoists or other handling aids are available.   

Suggestions for improvement, Items 6 to 8.5:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

V. Workplace/Workspace Design

Workplace may be diagrammatically illustrated, showing human reach and
clearance:

9. Workplace is compatible with human dimensions.              Yes/No

If No, rate the following:            (Enter 0-5)

9.1 Work distance is away from normal reach in the horizontal or vertical plane (>60 cm).   

9.2 Height of work desk/equipment is fixed or minimally adjustable.   

9.3 No space for subsidiary operations (e.g., inspection and maintenance).   

9.4 Workstations have obstacles, protruding parts or sharp edges.   

9.5 Work surface floors are slippery, uneven, cluttered or unstable.   

10. Seating arrangement is adequate  (e.g., comfortable chair,
good postural support).            Yes/No

If No, the causes are:            (Enter 0-5)

10.1 Seat dimensions (e.g., seat height, back rest) mismatch with human dimensions.   

10.2 Minimum adjustability of seat.   

10.3 Workseat provides no hold/support (e.g., by means of vertical edges/extra stiff covering) to work with the machinery.   

10.4 Absence of vibration damping mechanism in the workseat.   

11. Sufficient auxiliary support is available for safety
at the workplace.            Yes/No

If No, mention the following:            (Enter 0-5)

11.1 Non-availability of storage space for tools, personal articles.   

11.2 Doorways, entrance/exit routes, or corridors are restricted.  

11.3 Design mismatch of handles, ladders, staircases, handrails.   

11.4 Handholds and footholds demand awkward position of limbs.   

11.5 Supports are unrecognizable by their place, form or construction.   

11.6 Limited use of gloves/footwear to work and operate equipment controls.   

Suggestions for improvement, Items 9 to 11.6:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

VI. Work Posture

12. Job allows a relaxed work posture.            Yes/No

If No, rate the following:             (Enter 0-5)

12.1 Working with arms above shoulder and/or away from the body.   

12.2 Hyperextension of wrist and demand of high strength.   

12.3 Neck/shoulder are not maintained at an angle of about 15°.   

12.4 Back bent and twisted.   

12.5 Hips and legs are not well supported in seated position.   

12.6 One-sided and unsymmetrical movement of the body.   

12.7 Mention reasons of forced posture:
(1) machine location
(2) seat design,
(3) equipment handling,
(4) workplace/workspace

12.8 Specify OWAS code. (For a detailed description of the OWAS
method refer to Karhu et al. 1981.)

_______________________________________________________________

_______________________________________________________________

Suggestions for improvement, Items 12 to 12.7:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

VII. Work Environment

(Give measurements where possible)

NOISE

[Identify noise sources, type and duration of exposure; refer to ILO 1984 code].

13. Noise level is below the maximum              Yes/No
sound level recommended. (Use the following table.)

Source: Ahonen et al. 1989.

Give your agreement/disagreement score (0-5)  

14. Damaging noises are suppressed at the source.             Yes/No

If No, rate countermeasures:            (Enter 0-5)

14.1 No effective sound isolation present.   

14.2 Noise emergency measures are not taken (e.g., restriction of working time, use of personal ear defenders/protectors).   

15. CLIMATE

Specify climatic condition.

Temperature  ____

Humidity ____

Radiant Temperature ____

Draughts ____

16. Climate is comfortable.            Yes/No

If No, rate the following:            (Enter 0-5)

16.1 Temperature sensation (circle one):

cool/slightly cool/neutral/warm/very hot

16.2 Ventilation devices (e.g., fans, windows, air conditioners) are not adequate.   

16.3 Non-execution of regulatory measures on exposure limits (if available, please elaborate).   

16.4 Workers do not wear heat protective/assistive clothing.   

16.5 Drinking fountains of cool water are not available nearby.   

17. LIGHTING

Workplace/machine(s) are sufficiently illuminated at all times.            Yes/No

If No, rate the following:            (Enter 0-5)

17.1 Illumination is sufficiently intense.   

17.2 Illumination of work area is adequately uniform.   

17.3 Flicker phenomena are minimal or absent.   

17.4 Shadow formation is nonproblematical.   

17.5 Annoying reflected glares are minimal or absent.   

17.6 Colour dynamics (visual accentuation, colour warmth) are adequate.   

18. DUST, SMOKE, TOXICANTS

Environment is free from excessive dust, 
fumes and toxic substances.            Yes/No

If No, rate the following:            (Enter 0-5)

18.1 Ineffective ventilation and exhaust systems to carry off fumes, smoke and dirt.   

18.2 Lack of protection measures against emergency release and contact with dangerous/toxic substances.   

List the chemical toxicants:

_______________________________________________________________

_______________________________________________________________

18.3 Monitoring of the workplace for chemical toxicants is not regular.   

18.4 Non-availability of personal protective measures (e.g., gloves, shoes, mask, apron).   

19. RADIATION

Workers are effectively protected against radiation exposure.            Yes/No

If No, mention the exposures 
(see ISSA checklist, Ergonomics):            (Enter 0-5)

19.1 UV radiation (200 nm – 400 nm).   

19.2 IR radiation (780 nm – 100 μm).   

19.3 Radioactivity/x-ray radiation (<200 nm).   

19.4 Microwaves (1 mm – 1 m).   

19.5 Lasers (300 nm – 1.4 μm).   

19.6 Others (mention):

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

20. VIBRATION

Machine can be operated without vibration transmission
to the operator’s body.            Yes/No

If No, rate the following:            (Enter 0-5)

20.1 Vibration is transmitted to the whole body via the feet.   

20.2 Vibration transmission occurs through the seat (e.g., mobile machines that are driven with operator seated).   

20.3 Vibration is transmitted through the hand-arm system (e.g., power-driven handtools, machines driven when operator is walking).   

20.4 Prolonged exposure to continuous/repetitive source of vibration.   

20.5 Vibration sources cannot be isolated or eliminated.   

20.6 Identify the sources of vibration.

Comments and suggestions, items 13 to 20:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

VIII. Work Time Schedule

Indicate work time: work hours/day/week/year, including seasonal work and shift system.

21. Pressure of work time is minimum.            Yes/No

If No, rate the following:            (Enter 0-5)

21.1 Job requires night work.   

21.2 Job involves overtime/extra work time.   

Specify average duration:

_______________________________________________________________

21.3 Heavy tasks are unevenly distributed throughout the shift.   

21.4 People work at a predetermined pace/time limit.   

21.5 Fatigue allowances/work-rest patterns are not sufficiently incorporated (use cardio- respiratory criteria on work severity).   

Comments and suggestions, items 21 to 21.5:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

   Analyst’s rating       Worker’s ratin   

D. Perceptual/motor aspect    Your answers/ratings

IX. Displays

22. Visual displays (gauges, meters, warning signals) 
are easy to read.            Yes/No

If No, rate the difficulties:            (Enter 0-5)

22.1 Insufficient lighting (refer to item No. 17).   

22.2 Awkward head/eye positioning for visual line.   

22.3 Display style of numerals/numerical progression creates confusion and causes reading errors.   

22.4 Digital displays are not available for accurate reading.   

22.5 Large visual distance for reading precision.   

22.6 Displayed information is not easily understood.   

23. Emergency signals/impulses are easily recognizable.            Yes/No

If No, assess the reasons:

23.1 Signals (visual/auditory) do not conform to the work process.   

23.2 Flashing signals are out of visual field.   

23.3 Auditory display signals are not audible.   

24. Groupings of the display features are logical.            Yes/No

If No, rate the following:

24.1 Displays are not distinguished by form, position, colour or tone.   

24.2 Frequently used and critical displays are removed from the central line of vision.   

X. Controls

25. Controls (e.g., switches, knobs, cranes, driving wheels, pedals) are easy to handle.            Yes/No

If No, the causes are:            (Enter 0-5)

25.1 Hand/foot control positions are awkward.   

25.2 Handedness of the controls/tools is incorrect.   

25.3 Dimensions of controls do not match the operating body part.   

25.4 Controls require high actuating force.   

25.5 Controls require high precision and speed.   

25.6 Controls are not shape-coded for good grip.   

25.7 Controls are not colour/symbol-coded for identification.   

25.8 Controls cause unpleasant feeling (warmth, cold, vibration).   

26. Displays and controls (combined) are compatible with easy and comfortable human reactions.            Yes/No

If No, rate the following:            (Enter 0-5)

26.1 Placements are not sufficiently close to each other.   

26.2 Display/controls are not sequentially arranged for functions/frequency of use.   

26.3 Display/control operations are successive, without enough time span to complete operation (this creates sensory overloading).   

26.4 Disharmony in movement direction of display/control (e.g., leftward control movement does not give leftward unit movement).   

Comments and suggestions, items 22 to 26.4:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

   Analyst’s rating       Worker’s rating   

E. Technical aspect    Your answers/ratings

XI. Machinery

27. Machine (e.g., conveyer trolley, lifting truck, machine tool) 
is easy to drive and work with.            Yes/No

If No, rate the following:            (Enter 0-5)

27.1 Machine is unstable in operation.   

27.2 Poor maintenance of the machinery.   

27.3 Driving speed of the machine cannot be regulated.   

27.4 Steering wheels/handles are operated, from standing position.   

27.5 Operating mechanisms hamper body movements in the workspace.   

27.6 Risk of injury due to lack of machine guarding.   

27.7 Machinery is not equipped with warning signals.   

27.8 Machine is poorly equipped for vibration damping.   

27.9 Machine noise levels are above legal limits (refer to items No. 13 and 14)   

27.10 Poor visibility of machine parts and adjacent area (refer to items No. 17 and 22).   

XII. Small Tools/Implements

28. Tools/implements provided to the operatives are 
comfortable to work with.            Yes/No

If No, rate the following:            (Enter 0-5)

28.1 Tool/implement has no carrying strap/back frame.   

28.2 Tool cannot be used with alternate hands.   

28.3 Heavy weight of the tool causes hyperextension of the wrist.   

28.4 Form and position of the handle are not designed for convenient grip.   

28.5 Power-driven tool is not designed for two-hand operation.   

28.6 Sharp edges/ridges of the tool/equipment can cause injury.      

28.7 Harnesses (gloves, etc.) are not regularly used in operating vibrating tool.   

28.8 Noise levels of power-driven tool are above acceptable limits 
(refer to item No. 13).   

Suggestions for improvement, items 27 to 28.8:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

XIII. Work Safety

29. Machine safety measures are adequate to prevent 
accidents and health hazards.            Yes/No

If No, rate the following:            (Enter 0-5)

29.1 Machine accessories cannot be fastened and removed easily.   

29.2 Dangerous points, moving parts and electrical installations are not adequately guarded.   

29.3 Direct/indirect contact of body parts with machinery can cause hazards.   

29.4 Difficulty in inspection and maintenance of the machine.   

29.5 No clear instructions available for machine operation, maintenance and safety.   

Suggestions for improvement, items 29 to 29. 5:

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

   Analyst’s rating       Worker’s rating   

F. Psychosocial aspect    Your answers/ratings

XIV. Job Autonomy

30. Job allows autonomy (e.g., freedom regarding method of work, 
performance conditions, time schedule, quality control).            Yes/No

If No, the possible causes are:            (Enter 0-5)

30.1 No discretion on the starting/finishing times of the job.   

30.2 No organizational support as regards calling for assistance at work.   

30.3 Insufficient number of people for the task (teamwork).   

30.4 Rigidity in work methods and conditions.   

XV. Job Feedback (Intrinsic and Extrinsic)

31. Job allows direct feedback of information as to the quality 
and quantity of one’s performance.            Yes/No

If No, the reasons are:            (Enter 0-5)

31.1 No participative role in task information and decision making.   

31.2 Constraints of social contact due to physical barriers.   

31.3 Communication difficulty due to high noise level.   

31.4 Increased attentional demand in machine pacing.   

31.5 Other people (managers, co-workers) inform the worker as to his/her effectiveness of job performance.   

XVI. Task Variety/Clarity

32. Job has a variety of tasks and calls for spontaneity on the part of the worker.            Yes/No

If No, rate the following:            (Enter 0-5)

32.1 Job roles and goals are ambiguous.   

32.2 Job restrictiveness is imposed by a machine, process or work group.   

32.3 Worker-machine relation arouses conflict as to behaviour to be evinced by operator.   

32.4 Restricted level of stimulation (e.g., unchanging visual and auditory environment).   

32.5 High level of boredom on the job.   

32.6 Limited scope for job enlargement.   

XVII. Task Identity/Significance

33. Worker is given a batch of tasks             Yes/No
and arranges his or her own schedule to complete the work
(e.g., one plans and executes the job and inspects and
manages the products).

Give your agreement/disagreement score (0-5)   

34. Job is significant in the organization.            Yes/No
It provides acknowledgement and recognition from others.

(Give your agreement/disagreement score)

XVIII. Mental Overload/Underload

35. Job consists of tasks for which clear communication and 
unambiguous information support systems are available.            Yes/No

If No, rate the following:            (Enter 0-5)

35.1 Information supplied in connection with the job is extensive.   

35.2 Information handling under pressure is required (e.g., emergency manoeuvering in process control).   

35.3 High information-handling workload (e.g., difficult positioning task—no special motivation required).   

35.4 Occasional attention is directed to information other than that needed for the actual task.   

35.5 Task consists of repetitive simple motor act, with superficial attention needed.   

35.6 Tools/equipment are not pre-positioned to avoid mental delay.   

35.7 Multiple choices are required in decision making and judging risks.   

(Comments and suggestions, items 30 to 35.7)

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

_______________________________________________________________

XIX. Training and Promotion

36. Job has opportunities for associated growth in competence 
and task accomplishment.            Yes/No

If No, the possible causes are:            (Enter 0-5)

36.1 No opportunity for advancement to higher levels.   

36.2 No periodic training for operators, specific to jobs.   

36.3 Training programs/tools are not easy to learn and use.   

36.4 No incentive pay schemes.   

XX. Organizational Commitment

37. Defined commitment towards organizational            Yes/No
effectiveness, and physical, mental and social well-being.

Assess the degree to which the following are made available:            (Enter 0-5)

37.1 Organizational role in individual role conflicts and ambiguities.   

37.2 Medical/administrative services for preventive intervention in the case of work hazards.   

37.3 Promotional measures to control absenteeism in work group.   

37.4 Effective safety regulations.   

37.5 Labour inspection and monitoring of better work practices.   

37.6 Follow-up action for accident/injury management.   

The Summary Evaluation Sheet may be used for profiling and clustering of a selected group of items, which may form the basis for decisions on work systems. The process of analysis is often time-consuming and the users of these instruments must have a sound training in ergonomics both theoretical and practical, in the evaluation of work systems.

SUMMARY EVALUATION SHEET

A. Brief Description of Organization, Worker Characteristics and Task Description

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Overall Assessment

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This article is adapted from the 3rd edition of the Encyclopaedia of Occupational Health and Safety.

Anthropometry is a fundamental branch of physical anthropology. It represents the quantitative aspect. A wide system of theories and practice is devoted to defining methods and variables to relate the aims in the different fields of application. In the fields of occupational health, safety and ergonomics anthropometric systems are mainly concerned with body build, composition and constitution, and with the dimensions of the human body’s interrelation to workplace dimensions, machines, the industrial environment, and clothing.

Anthropometric variables

An anthropometric variable is a measurable characteristic of the body that can be defined, standardized and referred to a unit of measurement. Linear variables are generally defined by landmarks that can be precisely traced to the body. Landmarks are generally of two types: skeletal-anatomical, which may be found and traced by feeling bony prominences through the skin, and virtual landmarks that are simply found as maximum or minimum distances using the branches of a caliper.

Anthropometric variables have both genetic and environmental components and may be used to define individual and population variability. The choice of variables must be related to the specific research purpose and standardized with other research in the same field, as the number of variables described in the literature is extremely large, up to 2,200 having been described for the human body.

Anthropometric variables are mainly linear measures, such as heights, distances from landmarks with subject standing or seated in standardized posture; diameters, such as distances between bilateral landmarks; lengths, such as distances between two different landmarks; curved measures, namely arcs, such as distances on the body surface between two landmarks; and girths, such as closed all-around measures on body surfaces, generally positioned at at least one landmark or at a defined height.

Other variables may require special methods and instruments. For instance skinfold thickness is measured by means of special constant pressure calipers. Volumes are measured by calculation or by immersion in water. To obtain full information on body surface characteristics, a computer matrix of surface points may be plotted using biostereometric techniques.

Instruments

Although sophisticated anthropometric instruments have been described and used with a view to automated data collection, basic anthropometric instruments are quite simple and easy to use. Much care must be taken to avoid common errors resulting from misinterpretation of landmarks and incorrect postures of subjects.

The standard anthropometric instrument is the anthropometer—a rigid rod 2 metres long, with two counter-reading scales, with which vertical body dimensions, such as heights of landmarks from floor or seat, and transverse dimensions, such as diameters, can be taken.

Commonly the rod can be split into 3 or 4 sections which fit into one another. A sliding branch with a straight or curved claw makes it possible to measure distances from the floor for heights, or from a fixed branch for diameters. More elaborate anthropometers have a single scale for heights and diameters to avoid scale errors, or are fitted with digital mechanical or electronic reading devices (figure 1).

Figure 1. An anthropometer

A stadiometer is a fixed anthropometer, generally used only for stature and frequently associated with a weight beam scale.

For transverse diameters a series of calipers may be used: the pelvimeter for measures up to 600 mm and the cephalometer up to 300 mm. The latter is particularly suitable for head measurements when used together with a sliding compass (figure 2).

Figure 2. A cephalometer together with a sliding compass

The foot-board is used for measuring the feet and the head-board provides cartesian co-ordinates of the head when oriented in the “Frankfort plane” (a horizontal plane passing through porion and orbitale landmarks of the head).The hand may be measured with a caliper, or with a special device composed of five sliding rulers.

Skinfold thickness is measured with a constant-pressure skinfold caliper generally with a pressure of 9.81 x 10⁴ Pa (the pressure imposed by a weight of 10 g on an area of 1 mm²).

For arcs and girths a narrow, flexible steel tape with flat section is used. Self-straightening steel tapes must be avoided.

Systems of variables

A system of anthropometric variables is a coherent set of body measurements to solve some specific problems.

In the field of ergonomics and safety, the main problem is fitting equipment and workspace to humans and tailoring clothes to the right size.

Equipment and workspace require mainly linear measures of limbs and body segments that can easily be calculated from landmark heights and diameters, whereas tailoring sizes are based mainly on arcs, girths and flexible tape lengths. Both systems may be combined according to need.

In any case, it is absolutely necessary to have a precise space reference for each measurement. The landmarks must, therefore, be linked by heights and diameters and every arc or girth must have a defined landmark reference. Heights and slopes must be indicated.

In a particular survey, the number of variables has to be limited to the minimum so as to avoid undue stress on the subject and operator.

A basic set of variables for workspace has been reduced to 33 measured variables (figure 3) plus 20 derived by a simple calculation. For a general-purpose military survey, Hertzberg and co-workers use 146 variables. For clothes and general biological purposes the Italian Fashion Board (Ente Italiano della Moda) uses a set of 32 general purpose variables and 28 technical ones. The German norm (DIN 61 516) of control body dimensions for clothes includes 12 variables. The recommendation of the International Organization for Standardization (ISO) for anthropometry includes a core list of 36 variables (see table 1). The International Data on Anthropometry tables published by the ILO list 19 body dimensions for the populations of 20 different regions of the world (Jürgens, Aune and Pieper 1990).

Figure 3. Basic set of anthropometric variables

Table 1. Basic anthropometric core list

1.1            Forward reach (to hand grip with subject standing upright against a wall)

1.2            Stature (vertical distance from floor to head vertex)

1.3            Eye height (from floor to inner eye corner)

1.4            Shoulder height (from floor to acromion)

1.5            Elbow height (from floor to radial depression of elbow)

1.6            Crotch height (from floor to pubic bone)

1.7            Finger tip height (from floor to grip axis of fist)

1.8            Shoulder breadth (biacromial diameter)

1.9            Hip breadth, standing (the maximum distance across hips)

2.1            Sitting height (from seat to head vertex)

2.2            Eye height, sitting (from seat to inner corner of the eye)

2.3            Shoulder height, sitting (from seat to acromion)

2.4            Elbow height, sitting (from seat to lowest point of bent elbow)

2.5            Knee height (from foot-rest to the upper surface of thigh)

2.6            Lower leg length (height of sitting surface)

2.7            Forearm-hand length (from back of bent elbow to grip axis)

2.8            Body depth, sitting (seat depth)

2.9            Buttock-knee length (from knee-cap to rearmost point of buttock)

2.10            Elbow to elbow breadth (distance between lateral surface of the elbows)

2.11            Hip breadth, sitting (seat breadth)

3.1            Index finger breadth, proximal (at the joint between medial and proximal phalanges)

3.2            Index finger breadth, distal (at the joint between distal and medial phalanges)

3.3            Index finger length

3.4            Hand length (from tip of middle finger to styloid)

3.5            Handbreadth (at metacarpals)

3.6            Wrist circumference

4.1            Foot breadth

4.2            Foot length

5.1            Heat circumference (at glabella)

5.2            Sagittal arc (from glabella to inion)

5.3            Head length (from glabella to opisthocranion)

5.4            Head breadth (maximum above the ear)

5.5            Bitragion arc (over the head between the ears)

6.1            Waist circumference (at the umbilicus)

6.2            Tibial height (from the floor to the highest point on the antero-medial margin of the glenoid of the tibia)

6.3            Cervical height sitting (to the tip of the spinous process of the 7th cervical vertebra).

Source: Adapted from ISO/DP 7250 1980).

 Precision and errors

The precision of living body dimensions must be considered in a stochastic manner because the human body is highly unpredictable, both as a static and as a dynamic structure.

A single individual may grow or change in muscularity and fatness; undergo skeletal changes as a consequence of aging, disease or accidents; or modify behavior or posture. Different subjects differ by proportions, not only by general dimensions. Tall stature subjects are not mere enlargements of short ones; constitutional types and somatotypes probably vary more than general dimensions.

The use of mannequins, particularly those representing the standard 5th, 50th and 95th percentiles for fitting trials may be highly misleading, if body variations in body proportions are not taken into consideration.

Errors result from misinterpretation of landmarks and incorrect use of instruments (personal error), imprecise or inexact instruments (instrumental error), or changes in subject posture (subject error—this latter may be due to difficulties of communication if the cultural or linguistic background of the subject differs from that of the operator).

Statistical treatment

Anthropometric data must be treated by statistical procedures, mainly in the field of inference methods applying univariate (mean, mode, percentiles, histograms, variance analysis, etc.), bivariate (correlation, regression) and multivariate (multiple correlation and regression, factor analysis, etc.) methods. Various graphical methods based on statistical applications have been devised to classify human types (anthropometrograms, morphosomatograms).

Sampling and survey

As anthropometric data cannot be collected for the whole population (except in the rare case of a particularly small population), sampling is generally necessary. A basically random sample should be the starting point of any anthropometric survey. To keep the number of measured subjects to a reasonable level it is generally necessary to have recourse to multiple-stage stratified sampling. This allows the most homogeneous subdivision of the population into a number of classes or strata.

The population may be subdivided by sex, age group, geographical area, social variables, physical activity and so on.

Survey forms have to be designed keeping in mind both measuring procedure and data treatment. An accurate ergonomic study of the measuring procedure should be made in order to reduce the operator’s fatigue and possible errors. For this reason, variables must be grouped according to the instrument used and ordered in sequence so as to reduce the number of body flexions the operator has to make.

To reduce the effect of personal error, the survey should be carried out by one operator. If more than one operator has to be used, training is necessary to assure the replicability of measurements.

Population anthropometrics

Disregarding the highly criticized concept of “race”, human populations are nevertheless highly variable in size of individuals and in size distribution. Generally human populations are not strictly Mendelian; they are commonly the result of admixture. Sometimes two or more populations, with different origins and adaptation, live together in the same area without interbreeding. This complicates the theoretical distribution of traits. From the anthropometric viewpoint, sexes are different populations. Populations of employees may not correspond exactly to the biological population of the same area as a consequence of possible aptitudinal selection or auto-selection due to job choice.

Populations from different areas may differ as a consequence of different adaptation conditions or biological and genetic structures.

When close fitting is important a survey on a random sample is necessary.

Fitting trials and regulation

The adaptation of workspace or equipment to the user may depend not only on the bodily dimensions, but also on such variables as tolerance of discomfort and nature of activities, clothing, tools and environmental conditions. A combination of a checklist of relevant factors, a simulator and a series of fitting trials using a sample of subjects chosen to represent the range of body sizes of the expected user population can be used.

The aim is to find tolerance ranges for all subjects. If the ranges overlap it is possible to select a narrower final range that is not outside the tolerance limits of any subject. If there is no overlap it will be necessary to make the structure adjustable or to provide it in different sizes. If more than two dimensions are adjustable a subject may not be able to decide which of the possible adjustments will fit him best.

Adjustability can be a complicated matter, especially when uncomfortable postures result in fatigue. Precise indications must, therefore, be given to the user who frequently knows little or nothing about his own anthropometric characteristics. In general, an accurate design should reduce the need for adjustment to the minimum. In any case, it should constantly be kept in mind what is involved is anthropometrics, not merely engineering.

Dynamic anthropometrics

Static anthropometrics may give wide information about movement if an adequate set of variables has been chosen. Nevertheless, when movements are complicated and a close fit with the industrial environment is desirable, as in most user-machine and human-vehicle interfaces, an exact survey of postures and movements is necessary. This may be done with suitable mock-ups that allow tracing of reach lines or by photography. In this case, a camera fitted with a telephoto lens and an anthropometric rod, placed in the sagittal plane of the subject, allows standardized photographs with little distortion of the image. Small labels on subjects’ articulations make the exact tracing of movements possible.

Another way of studying movements is to formalize postural changes according to a series of horizontal and vertical planes passing through the articulations. Again, using computerized human models with computer-aided design (CAD) systems is a feasible way to include dynamic anthropometrics in ergonomic workplace design.

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Muscular Work in Occupational Activities

In industrialized countries around 20% of workers are still employed in jobs requiring muscular effort (Rutenfranz et al. 1990). The number of conventional heavy physical jobs has decreased, but, on the other hand, many jobs have become more static, asymmetrical and stationary. In developing countries, muscular work of all forms is still very common.

Muscular work in occupational activities can be roughly divided into four groups: heavy dynamic muscle work, manual materials handling, static work and repetitive work. Heavy dynamic work tasks are found in forestry, agriculture and the construction industry, for example. Materials handling is common, for example, in nursing, transportation and warehousing, while static loads exist in office work, the electronics industry and in repair and maintenance tasks. Repetitive work tasks can be found in the food and wood-processing industries, for example.

It is important to note that manual materials handling and repetitive work are basically either dynamic or static muscular work, or a combination of these two.

Physiology of Muscular Work

Dynamic muscular work

In dynamic work, active skeletal muscles contract and relax rhythmically. The blood flow to the muscles is increased to match metabolic needs. The increased blood flow is achieved through increased pumping of the heart (cardiac output), decreased blood flow to inactive areas, such as kidneys and liver, and increased number of open blood vessels in the working musculature. Heart rate, blood pressure, and oxygen extraction in the muscles increase linearly in relation to working intensity. Also, pulmonary ventilation is heightened owing to deeper breathing and increased breathing frequency. The purpose of activating the whole cardio-respiratory system is to enhance oxygen delivery to the active muscles. The level of oxygen consumption measured during heavy dynamic muscle work indicates the intensity of the work. The maximum oxygen consumption (VO_2max) indicates the person’s maximum capacity for aerobic work. Oxygen consumption values can be translated to energy expenditure (1 litre of oxygen consumption per minute corresponds to approximately 5 kcal/min or 21 kJ/min).

In the case of dynamic work, when the active muscle mass is smaller (as in the arms), maximum working capacity and peak oxygen consumption are smaller than in dynamic work with large muscles. At the same external work output, dynamic work with small muscles elicits higher cardio-respiratory responses (e.g., heart rate, blood pressure) than work with large muscles (figure 1).

Figure 1. Static versus dynamic work    

Static muscle work

In static work, muscle contraction does not produce visible movement, as, for example, in a limb. Static work increases the pressure inside the muscle, which together with the mechanical compression occludes blood circulation partially or totally. The delivery of nutrients and oxygen to the muscle and the removal of metabolic end-products from the muscle are hampered. Thus, in static work, muscles become fatigued more easily than in dynamic work.

The most prominent circulatory feature of static work is a rise in blood pressure. Heart rate and cardiac output do not change much. Above a certain intensity of effort, blood pressure increases in direct relation to the intensity and the duration of the effort. Furthermore, at the same relative intensity of effort, static work with large muscle groups produces a greater blood pressure response than does work with smaller muscles. (See figure 2)

Figure 2. The expanded stress-strain model modified from Rohmert (1984)

In principle, the regulation of ventilation and circulation in static work is similar to that in dynamic work, but the metabolic signals from the muscles are stronger, and induce a different response pattern.

Consequences of Muscular Overload in Occupational Activities

The degree of physical strain a worker experiences in muscular work depends on the size of the working muscle mass, the type of muscular contractions (static, dynamic), the intensity of contractions, and individual characteristics.

When muscular workload does not exceed the worker’s physical capacities, the body will adapt to the load and recovery is quick when the work is stopped. If the muscular load is too high, fatigue will ensue, working capacity is reduced, and recovery slows down. Peak loads or prolonged overload may result in organ damage (in the form of occupational or work-related diseases). On the other hand, muscular work of certain intensity, frequency, and duration may also result in training effects, as, on the other hand, excessively low muscular demands may cause detraining effects. These relationships are represented by the so-called expanded stress-strain concept developed by Rohmert (1984) (figure 3).

Figure 3. Analysis of acceptable workloads

In general, there is little epidemiological evidence that muscular overload is a risk factor for diseases. However, poor health, disability and subjective overload at work converge in physically demanding jobs, especially with older workers. Furthermore, many risk factors for work-related musculoskeletal diseases are connected to different aspects of muscular workload, such as the exertion of strength, poor working postures, lifting and sudden peak loads.

One of the aims of ergonomics has been to determine acceptable limits for muscular workloads which could be applied for the prevention of fatigue and disorders. Whereas the prevention of chronic effects is the focus of epidemiology, work physiology deals mostly with short-term effects, that is, fatigue in work tasks or during a work day.

Acceptable Workload in Heavy Dynamic Muscular Work

The assessment of acceptable workload in dynamic work tasks has traditionally been based on measurements of oxygen consumption (or, correspondingly, energy expenditure). Oxygen consumption can be measured with relative ease in the field with portable devices (e.g., Douglas bag, Max Planck respirometer, Oxylog, Cosmed), or it can be estimated from heart rate recordings, which can be made reliably at the workplace, for example, with the SportTester device. The use of heart rate in the estimation of oxygen consumption requires that it be individually calibrated against measured oxygen consumption in a standard work mode in the laboratory, i.e., the investigator must know the oxygen consumption of the individual subject at a given heart rate. Heart rate recordings should be treated with caution because they are also affected by such factors as physical fitness, environmental temperature, psychological factors and size of active muscle mass. Thus, heart rate measurements can lead to overestimates of oxygen consumption in the same way that oxygen consumption values can give rise to underestimates of global physiological strain by reflecting only energy requirements.

Relative aerobic strain (RAS) is defined as the fraction (expressed as a percentage) of a worker’s oxygen consumption measured on the job relative to his or her VO_2max measured in the laboratory. If only heart rate measurements are available, a close approximation to RAS can be made by calculating a value for percentage heart rate range (% HR range) with the so-called Karvonen formula as in figure 3.

VO_2max is usually measured on a bicycle ergometer or treadmill, for which the mechanical efficiency is high (20-25%). When the active muscle mass is smaller or the static component is higher, VO_2max and mechanical efficiency will be smaller than in the case of exercise with large muscle groups. For example, it has been found that in the sorting of postal parcels the VO_2max of workers was only 65% of the maximum measured on a bicycle ergometer, and the mechanical efficiency of the task was less than 1%. When guidelines are based on oxygen consumption, the test mode in the maximal test should be as close as possible to the real task. This goal, however, is difficult to achieve.

According to Åstrand’s (1960) classical study, RAS should not exceed 50% during an eight-hour working day. In her experiments, at a 50% workload, body weight decreased, heart rate did not reach steady state and subjective discomfort increased during the day. She recommended a 50% RAS limit for both men and women. Later on she found that construction workers spontaneously chose an average RAS level of 40% (range 25-55%) during a working day. Several more recent studies have indicated that the acceptable RAS is lower than 50%. Most authors recommend 30-35% as an acceptable RAS level for the entire working day.

Originally, the acceptable RAS levels were developed for pure dynamic muscle work, which rarely occurs in real working life. It may happen that acceptable RAS levels are not exceeded, for example, in a lifting task, but the local load on the back may greatly exceed acceptable levels. Despite its limitations, RAS determination has been widely used in the assessment of physical strain in different jobs.

In addition to the measurement or estimation of oxygen consumption, other useful physiological field methods are also available for the quantification of physical stress or strain in heavy dynamic work. Observational techniques can be used in the estimation of energy expenditure (e.g., with the aid of the Edholm scale) (Edholm 1966). Rating of perceived exertion (RPE) indicates the subjective accumulation of fatigue. New ambulatory blood pressure monitoring systems allow more detailed analyses of circulatory responses.

Acceptable Workload in Manual Materials Handling

Manual materials handling includes such work tasks as lifting, carrying, pushing and pulling of various external loads. Most of the research in this area has focused on low back problems in lifting tasks, especially from the biomechanical point of view.

A RAS level of 20-35% has been recommended for lifting tasks, when the task is compared to an individual maximum oxygen consumption obtained from a bicycle ergometer test.

Recommendations for a maximum permissible heart rate are either absolute or related to the resting heart rate. The absolute values for men and women are 90-112 beats per minute in continuous manual materials handling. These values are about the same as the recommended values for the increase in heart rate above resting levels, that is, 30 to 35 beats per minute. These recommendations are also valid for heavy dynamic muscle work for young and healthy men and women. However, as mentioned previously, heart rate data should be treated with caution, because it is also affected by other factors than muscle work.

The guidelines for acceptable workload for manual materials handling based on biomechanical analyses comprise several factors, such as weight of the load, handling frequency, lifting height, distance of the load from the body and physical characteristics of the person.

In one large-scale field study (Louhevaara, Hakola and Ollila 1990) it was found that healthy male workers could handle postal parcels weighing 4 to 5 kilograms during a shift without any signs of objective or subjective fatigue. Most of the handling occurred below shoulder level, the average handling frequency was less than 8 parcels per minute and the total number of parcels was less than 1,500 per shift. The mean heart rate of the workers was 101 beats per minute and their mean oxygen consumption 1.0 l/min, which corresponded to 31% RAS as related to bicycle maximum.

Observations of working postures and use of force carried out for example according to OWAS method (Karhu, Kansi and Kuorinka 1977), ratings of perceived exertion and ambulatory blood pressure recordings are also suitable methods for stress and strain assessments in manual materials handling. Electromyography can be used to assess local strain responses, for example in arm and back muscles.

Acceptable Workload for Static Muscular Work

Static muscular work is required chiefly in maintaining working postures. The endurance time of static contraction is exponentially dependent on the relative force of contraction. This means, for example, that when the static contraction requires 20% of the maximum force, the endurance time is 5 to 7 minutes, and when the relative force is 50%, the endurance time is about 1 minute.

Older studies indicated that no fatigue will be developed when the relative force is below 15% of the maximum force. However, more recent studies have indicated that the acceptable relative force is specific to the muscle or muscle group, and is 2 to 5% of the maximum static strength. These force limits are, however, difficult to use in practical work situations because they require electromyographic recordings.

For the practitioner, fewer field methods are available for the quantification of strain in static work. Some observational methods (e.g., the OWAS method) exist to analyse the proportion of poor working postures, that is, postures deviating from normal middle positions of the main joints. Blood pressure measurements and ratings of perceived exertion may be useful, whereas heart rate is not so applicable.

Acceptable Workload in Repetitive Work

Repetitive work with small muscle groups resembles static muscle work from the point of view of circulatory and metabolic responses. Typically, in repetitive work muscles contract over 30 times per minute. When the relative force of contraction exceeds 10% of the maximum force, endurance time and muscle force start to decrease. However, there is wide individual variation in endurance times. For example, the endurance time varies between two to fifty minutes when the muscle contracts 90 to 110 times per minute at a relative force level of 10 to 20% (Laurig 1974).

It is very difficult to set any definitive criteria for repetitive work, because even very light levels of work (as with the use of a microcomputer mouse) may cause increases in intramuscular pressure, which may sometimes lead to swelling of muscle fibres, pain and reduction in muscle strength.

Repetitive and static muscle work will cause fatigue and reduced work capacity at very low relative force levels. Therefore, ergonomic interventions should aim to minimize the number of repetitive movements and static contractions as far as possible. Very few field methods are available for strain assessment in repetitive work.

Prevention of Muscular Overload

Relatively little epidemiological evidence exists to show that muscular load is harmful to health. However, work physiological and ergonomic studies indicate that muscular overload results in fatigue (i.e., decrease in work capacity) and may reduce productivity and quality of work.

The prevention of muscular overload may be directed to the work content, the work environment and the worker. The load can be adjusted by technical means, which focus on the work environment, tools, and/or the working methods. The fastest way to regulate muscular workload is to increase the flexibility of working time on an individual basis. This means designing work-rest regimens which take into account the workload and the needs and capacities of the individual worker.

Static and repetitive muscular work should be kept at a minimum. Occasional heavy dynamic work phases may be useful for the maintenance of endurance type physical fitness. Probably, the most useful form of physical activity that can be incorporated into a working day is brisk walking or stair climbing.

Prevention of muscular overload, however, is very difficult if a worker’s physical fitness or working skills are poor. Appropriate training will improve working skills and may reduce muscular loads at work. Also, regular physical exercise during work or leisure time will increase the muscular and cardio-respiratory capacities of the worker.

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