Of course, you have to be good at description in order for that to work. As well as Saunders-Roe and Vickers which combined in to form the British Hovercraft Corporation BHC , other commercial craft were developed during the s in the UK by Cushioncraft part of the Britten-Norman Group and Hovermarine based at Woolston the latter being sidewall hovercraft , where the sides of the hull projected down into the water to trap the cushion of air with normal hovercraft skirts at the bow and stern. The Star Queen had been built in space and could never have lifted herself even from the surface of the Moon. Unfortunately such doors need even more space around the edge for the petals to retract into. Muscles can only contract, so for any joint there must be one muscle or muscle group to move it one way and a corresponding muscle or muscle group to move it in the opposite direction.
Generally speaking, when the nature of the work allows, concomitant and spontaneous evidence are to be preferred. They are free of various drawbacks such as unreliability of memory, observer interference, the effect of rationalizing reconstruction on the part of the subject, and so forth. To illustrate these distinctions, we will take the example of verbalizations. Both types can be done in real time, during work, and are thus concomitant. As for the validity of the verbalizations, the reader should not ignore the doubt raised in this regard by the controversy between Nisbett and De Camp Wilson and White and the precautions suggested by numerous authors aware of their importance in the study of mental activity in view of the methodological difficulties encountered Ericson and Simon ; Savoyant and Leplat ; Caverni ; Bainbridge The organization of this evidence, its processing and its formalization require descriptive languages and sometimes analyses which go beyond field observation.
Those mental activities which are inferred from the evidence, for example, remain hypothetical. Today they are often described using languages derived from artificial intelligence, making use of representations in terms of schemes, production rules and connecting networks.
Finally, we must mention the cognitive modellings of certain mental activities extracted from the field. Measurement of the discrepancies between the performance of these models and that of real, living operators is a fruitful field in activity analysis.
Performance is the outcome of the activity, the final response given by the subject to the requirements of the task. It is expressed at the level of production: But it must also be identified at the individual level: There exists a set of norms which, up to a certain point, guide the observer.
While in the vast majority of cases, work is a collective act, most work analyses focus on tasks or individual activities. Nonetheless the fact is that technological evolution, just like work organization, today emphasizes distributed work, whether it be between workers and machines or simply within a group.
What paths have been explored by authors so as to take this distribution into account Rasmussen, Pejtersen and Schmidts ? They focus on three aspects: Whether we view structure as elements of the analysis of people, or of services, or even of different branches of a firm working in a network, the description of the links that unite them remains a problem.
Other descriptions of distributed activities are possible: More recently, the need for firms to represent their information exchanges at a global level has led to a rethinking of information systems. The analysis of communications within teams has become a favoured means of capturing the very nature of collective work, encompassing subjects mentioned, creation of a common language in a team, modification of communications when circumstances are critical, and so forth Tardieu, Nanci and Pascot ; Rolland ; Navarro ; Van Daele ; Lacoste ; Moray, Sanderson and Vincente Knowledge of these interactions is particularly useful for the creation of computer tools, notably decision-making aids for understanding errors.
The different stages and the methodological difficulties linked to the use of this evidence have been well described by Falzon Studies such as those of Rogalski , who over a long period analysed the collective activities dealing with forest fires in France, and Bourdon and Weill Fassina , who studied the organizational structure set up to deal with railway accidents, are both very informative.
They clearly show how the context moulds the structure of exchanges, the number and type of actors involved, the nature of the communications and the number of parameters essential to the work.
The more this context fluctuates, the further the fixed descriptions of the task are removed from reality. Knowledge of this lability, and a better understanding of the phenomena that take place within it, are essential in planning for the unpredictable and in order to provide better training for those involved in collective work in a crisis.
The various phases of the work analysis that have been described are an iterative part of any human factors design cycle see figure In this design of any technical object, whether a tool, a workstation or a factory, in which human factors are a consideration, certain information is needed in time. In general, the beginning of the design cycle is characterized by a need for data involving environmental constraints, the types of jobs that are to be carried out, and the various characteristics of the users.
This initial information allows the objects specifications to be drawn up so as to take into account work requirements. But this is, in some sense, only a coarse model compared to the real work situation.
This explains why models and prototypes are necessary that, from their inception, allow not the jobs themselves, but the activities of the future users to be evaluated. Consequently, while the design of the images on a monitor in a control room can be based on a thorough cognitive analysis of the job to be done, only a data-based analysis of the activity will allow an accurate determination of whether the prototype will actually be of use in the actual work situation Van Daele Once the finished technical object is put into operation, greater emphasis is put on the performance of the users and on dysfunctional situations, such as accidents or human error.
The gathering of this type of information allows the final corrections to be made that will increase the reliability and usability of the completed object. Both the nuclear industry and the aeronautics industry serve as example: In this way, the design loop comes full circle.
Standardization in the field of ergonomics has a relatively short history. It started in the beginning of the s when the first committees were founded on the national level e.
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 , 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. 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:. 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.
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 a 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 a, 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. 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. 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.
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.
Ergonomics standards, like other standards, are produced in the appropriate technical committees TCs , their subcommittees SCs or working groups WGs.
Besides the ergonomics committees, ergonomics is also dealt with in TCs working on machine safety e. 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. With some of these the ergonomics committees do have liaisons in order to avoid duplication of work or inconsistent specifications; with some organizations e. 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. Ergonomics standardization committees are quite similar to one another in structure.
Usually one TC within a standardization organization is responsible for ergonomics. 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.
SCs within ISO TC 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.
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 , 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. 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. 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 , 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.
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: Whereas CEN TC is bound by the decisions of the EU administration and gets mandated work items to stipulate the specifications of European directives, ISO TC 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. 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. 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. International ergonomics standardization started with guidelines on the general principles of ergonomics in the design of work systems; they were laid down in ISO , which is now under revision in order to incorporate new developments.
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 , Part 1, defines terms and concepts e. SC 3 of ISO TC and WG 1 of CEN TC 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 shows how technological and social changes affect ergonomics standardization and the programme of such a subcommittee. 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. 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 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.
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 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.
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. 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 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.
The PAQ has six major divisions, comprising behavioural items required for the assessment of job performance and seven supplementary items related to monetary compensation:. The introductory section deals with the details of the organization, job descriptions and biographical details of the job holder. Other sections are as follows:. 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 , 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.
Each of the items of the AET are coded: The Man-at-Work system items includes the work objects, tools and equipment, and work environment constituting the physical, organizational, social and economic conditions of work.
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. Broadly speaking, the checklists adopt one of two approaches, 1 the job-oriented approach e. 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 ; Mossholder and Arvey ; Carter and Biersner , inferring job component validity and job stress Jeanneret ; Shaw and Riskind From the medical point of view, both the AET and the profile methods allow comparisons of constraints and aptitudes when required Wagner The Nordic questionnaire is an illustrative presentation of ergonomic workplace analysis Ahonen, Launis and Kuorinka , which covers the following aspects:.
Among the shortcomings of the general-purpose checklist format employed in ergonomic job analysis are the following:. The existing checklists refer less to underuse of abstract thought mechanisms than to overuse of concrete thought mechanisms. 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. Data collection and computerized processing of the checklist data are relatively straightforward, by responding to the primary and secondary statements q.
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. 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.
Description of organization and functions. A brief account of the work group. List activities and materials in use. Give some indication of the work hazards.
Job requires simple motor act. O Remarks and suggestions for improvement. Items 4 to 5. Physical activity is entirely determined and regulated by the worker. Job requires minimal MMH activity. Task situation is free from risk of bodily injury. Suggestions for improvement, Items 6 to 8. Workplace is compatible with human dimensions.
Sufficient auxiliary support is available for safety at the workplace. O Suggestions for improvement, Items 9 to Job allows a relaxed work posture. Noise level is below the maximum sound level recommended. Use the following table.
Damaging noises are suppressed at the source. List the chemical toxicants: Comments and suggestions, items 13 to Pressure of work time is minimum. O Comments and suggestions, items 21 to Visual displays gauges, meters, warning signals are easy to read. Groupings of the display features are logical. Displays and controls combined are compatible with easyand comfortable human reactions. O Comments and suggestions, items 22 to O Suggestions for improvement, items 27 to Machine safety measures are adequate to prevent accidents and health hazards.
O Suggestions for improvement, items 29 to Job allows autonomy e. Job has a variety of tasks and calls for spontaneity on the part of the worker. Worker is given a batch of tasks and arranges his or her own schedule to complete the work e. Job is significant in the organization. It provides acknowledgement and recognition from others.
Job consists of tasks for which clear communication and unambiguous information support systems are available. O Comments and suggestions, items 30 to Job has opportunities for associated growth in competence and task accomplishment. Defined commitment towards organizational effectiveness, and physical, mental and social well-being. O Now go to the Summary Evaluation Sheet. 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. 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 on the body. Landmarks are generally of two types: 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, 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.
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. 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 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 latter is particularly suitable for head measurements when used together with a sliding compass figure 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. For arcs and girths a narrow, flexible steel tape with flat section is used. Self-straightening steel tapes must be avoided. A system of anthropometric variables is a coherent set of body measurements to solve some specific problem. In the field of ergonomics and safety the main problem is fitting equipment and work space to humans and tailoring clothes to the right size.
Equipment and work space 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 work space has been reduced to 33 measured variables figure For a general purpose military survey, Hertzberg and co-workers use 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 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 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 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 ageing, disease or accidents; or modify behaviour 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. Anthropometric data must be treated by statistical procedures, mainly in the field of inference methods applying univariate mean, mode, percentiles, histograms, variance analysis, etc.
Various graphical methods based on statistical applications have been devised to classify human types anthropometrograms, morphosomatograms. 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.
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 replicability of measurements. 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. The adaptation of work space 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 check list 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 which 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. 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 telephoto lens and an anthropometric rod, placed in the sagittal plane of the subject, allows standardized photographs with little distortion of image.
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.
Juhani Smolander and Veikko Louhevaara. 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 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. 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. 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.
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.
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.
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. 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 figure 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.
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. 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.
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.
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. 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. 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. Rating of perceived exertion RPE indicates the subjective accumulation of fatigue. New ambulatory blood pressure monitoring systems allow more detailed analyses of circulatory responses.
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. 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 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 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, per shift.
The mean heart rate of the workers was beats per minute and their mean oxygen consumption 1. Observations of working postures and use of force carried out for example according to OWAS method Karhu, Kansi and Kuorinka , 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. 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. 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. Blood pressure measurements and ratings of perceived exertion may be useful, whereas heart rate is not so applicable. 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.
However, there is wide individual variation in endurance times. 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. Relatively little epidemiological evidence exists to show that muscular load is harmful to health. The truck itself is a Ford Raptor Supercrew with only 8, miles on it. The owner loves his Raptor but still wanted more performance than a simple bolt on kit, and decided to build the truck as a fully functioning street legal prerunner to take to the races and cruise in the desert.
We will post more info on the front suspension and rear 4-link as we get closer to finishing them up. Is he running the stock bed and front, or is he running some aftermarket parts? Tubework looks familiar, Great fabricators think alike! Good luck on the build. So this will have the same kit as the outlaw prerunner raptor?
Excited to see how it comes out. Andrew Well-Known Member Jul 28, Did he start with a raptor or an f? I never understand the people that buy raptors, then change out all the suspension and flares. Dawn Patrol Member Jul 28, There's a market out there for Raptor oem take off parts. Definitely drops the base price considerably when you're getting good money for all the parts you're swapping out.
Any updates on this build? Helgor Member Jan 28, It's going to be 4WD just gave a little sneak peak of the front end.
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