1. The history of the chair – A look back

The inhumane working conditions of early industrialization and the 19th-century mechanistic worldview's belief in the feasibility of creating desired "good" conditions through planned intervention suggested the need to establish a separate scientific discipline focused on the world of work. As early as 1857, the Pole Jastrzebowski proposed this in the journal "Nature and Industry."

“…to engage with a scientific approach to the problem of work and even to develop a separate doctrine for its (work's) explanation… so that we may reap the best fruits from this life with the least effort and the highest satisfaction for our own and the common good, and thus act justly towards others and our own conscience.”

He called this new branch of science "work science" or "ergonomics," a term that subsequently fell into oblivion. Since the mid-19th century, numerous activities have been observed in various countries that focused on the scientific study of human work. According to the prevailing scientific worldview, it was considered possible, in particular, to apply rules from classical physics to all phenomena in nature, including those of human life (see various works by Releaux and the psychophysics of Fechner). In various European countries and the USA, a field of science thus emerged that is now summarized in German-speaking countries under the term "work science" (in Anglo-American circles, the terms "human factors" or "human engineering" became established, and specifically in Europe, "ergonomics" is also used; see below). In Germany, the Kaiser Wilhelm Institute for Work Physiology was established in Berlin in 1912 under Atzler, and the Institute for Forest Work Science was founded in 1926 under Hilf. The Reich Committee for Time and Attendance (REFA, from 1936: Reich Committee for Work Studies; from 1948: Association for Work Studies REFA e.V.), founded in 1924, originally set itself the task of adapting and introducing Taylor's methods of scientific management (time and motion studies, differential pay system) to German conditions. In 1949, the neologism "ergonomics," composed of the ancient Greek words (ergon = work and nomos = law, regularity), was "reinvented" in England by Murrell. From this time onward, scientific societies bearing this name (in Germany, in 1953: "Gesellschaft für Arbeitswissenschaft, GfA") were founded in various European countries as well as in non-European countries. In 1959, they were united under the umbrella of the International Ergonomic Association (IEA). The Kaiser Wilhelm Institute for Occupational Physiology later relocated to Dortmund and, after World War II, as the Max Planck Institute for Occupational Physiology, became a key source for filling the chairs of ergonomics established at many technical universities in the 1960s. The then Technical University of Munich (TUM) established the Institute of Ergonomics in 1962, together with the Institute of Occupational Physiology. The Institute of Ergonomics, headed from the outset by Prof. Dr. H. Schmidtke, merged with the latter in 1990 and became the Chair of Ergonomics within the Institute of Production Engineering in the Department of Mechanical Engineering at TUM. Prof. Dr. [Name missing in original text] assumed leadership of the chair in 1993. H. Bubb and 2009 Prof. Dr. phil. K. Bengler.

2. The beginning of Human Factors Engineering

Regarding the scope of this emerging field, opinions differ. In the preface to his comprehensive work on the subject, W. E. Woodson (1981) writes: "Human Factors Engineering is the practice of designing products in such a way that the user can perform the required use, handling, operation, and supporting tasks with a minimum of stress and a maximum of efficiency." He also mentions the term "ergonomics," which, according to him, is generally used interchangeably with the term Human Factors Engineering. The only discernible difference is that the term "Human Factors Engineering" is more widespread in the USA than in other countries. M. Helander (1981), who served for many years as president of the IEA, offers a broader definition: "Human Factors Engineering seeks to modify work processes and tools in such a way as to take into account the physical and psychological capabilities and limitations of humans." He lists various terms for this discipline, such as "engineering psychology," "technical psychology," and—especially common in Europe—"ergonomics." In a study for the German Society for Ergonomics (GfA), the team of authors Luczak and Volpert et al. (1987), referring to research practice in German-speaking countries, found that ergonomics encompasses all disciplines that deal with working people—from medicine, psychology, and sociology to technology and law. According to this definition, ergonomics is the systematic analysis, organization, and design of the technical, organizational, and social conditions of work processes with the aim that working people find safe, feasible, and impairment-free working conditions in productive and efficient work processes; that standards of social appropriateness are met in terms of job content, job analysis, work environment, remuneration, and cooperation; that they can develop scope for action, acquire skills, and maintain and develop their personality in cooperation with others.

Ergonomics (internationally known as "ergonomics," see above) is a multidisciplinary science that draws its fundamental knowledge from the humanities, engineering, and economic and social sciences. It encompasses occupational medicine, psychology, education, technology, and law, as well as industrial sociology. Each of these fields addresses human work from its own perspective and thus represents one of its respective aspect sciences. With regard to practical application, this fundamental knowledge is summarized in so-called praxeologies. The more social-science-oriented of these is macro-ergonomics, which provides rules for the design of organizations, companies, and work groups; the more engineering-oriented is micro-ergonomics, which aims to provide rules for the technical design of workplaces and work equipment (see also Fig. 1). In both cases, the specific focus of research is on the individual and their experience of the workplace situation. Regarding the concept of work, two perspectives must be distinguished: work in its original, subjective sense as exertion (High German "arebeit" = toil, hardship) and work in the object-related sense of the "product" as the production of goods and services (Luzcak, 1998). The latter can also be considered the generation of information through individual effort (Bubb, 1987), which corresponds to the term "value creation" used in economic terminology. The aim of work science/ergonomics is therefore to reduce the subjective burden of work while simultaneously improving the object-related performance in the creation of the product. Individual performance in carrying out work is thus influenced by external conditions (external performance shaping factors), i.e., the objective performance requirements, and by internal conditions (internal performance shaping factors), i.e., the respective individual performance prerequisites (see Fig. 2). It is the responsibility of management to create the conditions for optimal human performance by shaping the external environment. This establishes the link between micro- and macro-ergonomics.

3. Ergonomics - Micro ergonomics

3.1 Grundlegende Ergonomie

The central aim of ergonomics (in the German sense; internationally: "micro ergonomics") is to contribute to improving the performance of the entire work system and reducing the strain on the worker by analyzing the task, the work environment, and human-machine interaction (Schmidtke, 1993). The classic approach to evaluating work systems utilizes the stress-strain concept. Its basic premise is that every workplace is characterized by external conditions that are the same for every individual working there (stress), but to which reactions vary depending on individual characteristics and abilities (strain). A more detailed analysis of stress can distinguish between stress magnitudes (in principle quantifiable numerically), stress factors (in principle only describable), and stress duration. An understanding of the factors influencing work can be gained by examining the structure of the human-machine system (HMS) (see also Fig. 3). This is obtained by examining human activity in terms of the information it contains and the associated information change. This includes a task or assignment and its execution, as well as the task completion or the result. The arrow indicating feedback closes the control loop formed by the MMS and shows that the operator is generally able to compare task and result. All influences acting on this process (insofar as they do not originate from process- or system-inherent influences) are referred to as environmental influences.

The stress-strain concept described above can be applied to the stress caused by the task and the stress caused by the environment. When analyzing the task, a distinction is made between...

• Tasks with a predominantly physical character (so-called "physical work"). A distinction is made here between static and dynamic physical work. In both cases, the workload can be quantified by specifying the physical performance requirements.
• Tasks with a predominantly mental character (so-called "mental work"). There is no universal concept for numerically defining the workload; therefore, mental work is generally treated as a workload factor.
• Tasks with a mixed character (so-called "mixed work").

When analyzing environmental influences (so-called "environmental ergonomics"), a distinction is made between...

• Physical environmental influences that can be measured and their effects on humans, which can be quantitatively assessed, are essential. These include, in particular, lighting, noise, mechanical vibrations, climate, toxic gases and vapors, radiation exposure, dust, dirt, and moisture.
• Social environmental influences, which are fundamentally impossible to measure using physical methods and therefore must be analyzed using other techniques (the task of so-called industrial sociology, and to some extent industrial psychology; see also 4.2).

Another subfield of ergonomics is the analysis of the human-machine system (HMS) in the narrower sense. This analysis can be carried out on the one hand with regard to the geometric design of the workplace and work equipment (so-called "anthropometric workplace design") and on the other hand with regard to the flow of information within the human-machine system (so-called "system ergonomics," see below). Anthropometric workplace design refers to the design of the visual, reach, and foot space, body supports (e.g., seats), as well as the design and arrangement of displays and controls. In addition to knowledge of the relevant sensory-physiological limitations and conditions (e.g., visual acuity, movement accuracy of the extremities) that are necessary for the design of displays and controls, the different sizes of people play a primary role in the design of the reach and foot space and body supports. Percentileizing individual body dimensions is used to systematically address this issue. Furthermore, to facilitate the often complex geometric design tasks, computer-generated geometric human models (3D models) were developed, which allow the construction of workplaces in CAD.

3.2 Ergonomics at the system level

The fundamental structure of human integration into a complex human-machine system (HMS) can be examined using systems analysis. Its goal is to obtain design requirements for human-machine interaction within the framework of the HMS specification or to identify potential improvements to existing systems. Since systems ergonomics aims to optimize this interaction, it also contributes to reducing the probability of human error (so-called "active safety") and/or increasing the reliability of the overall HMS performance. A key approach in systems ergonomics is to determine the system elements and their interrelationships (Bubb and Schmidtke, 1993). Two principles of this approach should be emphasized:

• Information is always transferred via very specific channels from the output of one element to the input of another.
• Elements are defined by their ability to transform information in a specific way, determined by the element itself.

A fundamental characteristic of systems analysis, and thus of systems ergonomics, is that it disregards the physical nature of the elements and their interactions, focusing solely on the formal structure of these interactions and the nature of information exchange between the elements. In systems ergonomics, the human system component and the machine system component are the primary focus. Since the analysis—as mentioned—is independent of the physical nature of the respective elements, the results of systems ergonomics research can be applied to various human-machine systems (HMS).

Deterministic Perspective: If the properties of elements within a system are described by functions, then, in principle, a uniquely assigned output or result function can be predicted based on a given input function. This idea corresponds to the usual cause-and-effect thinking. Although it is difficult—if not impossible—in most cases to describe human behavior in terms of mathematical functions (in specific cases, this is done, for example, in the form of a "paper pilot"), the cause-and-effect principle is still assumed here as well. So-called cognitive models of humans are developed that are intended to allow the prediction of human behavior in task situations presented by the MMS (Human-Machine System). At least in this way, the specific influence of measures (e.g., changes to displays or controls) on work performance can be predicted. Furthermore, changes to the system structure that accommodate human characteristics and abilities can be derived from such a perspective. This deterministic aspect of systems ergonomics thus makes it possible to derive constructive suggestions for improving human-machine interaction. Software ergonomics is a specialized field within systems ergonomics, focusing on the specific adaptation of computer programs to human characteristics. A large portion of software ergonomic recommendations has been developed for the design of the user interface (essentially the arrangement of information and controls on the screen). Furthermore, software ergonomic research and recommendations address the human-centered design of operating sequences dictated by the program structure. 

Random-Oriented Analysis: The system-ergonomic analysis of the MMS can be combined with a reliability analysis or estimation to evaluate the effectiveness of MMS optimization measures based on system-ergonomic analyses. Like system analysis, reliability analysis requires a breakdown of the MMS into elements and their interactions. By estimating the reliability or probability of failure of the elements, linking this with the rules of Boolean algebra while considering the system structure, and calculating the expected overall failure probability, it is possible not only to identify the elements that have the strongest influence on the overall failure probability, but also to improve the failure probability by modifying the system structure—which, of course, must be done in such a way that the overall function is maintained. Among other things, this approach, which includes the human element in the analysis, can lead to changes in the organization and organizational regulations. The probabilistic approach outlined here should not be seen as an alternative to classical cause-and-effect thinking. The function of a system can only be understood and methodically designed using this latter approach. In contrast, the probabilistic method primarily serves an evaluative function. This evaluation can be important during the design phase, as it allows for the differentiation of significant design influences from less significant ones. This is particularly relevant for assessing the cost-effectiveness of an ergonomic measure.

3.3 Application of Basic Ergonomics and System Ergonomics

Ergonomics is often categorized according to its areas of application. A particular distinction is made between product ergonomics and production ergonomics. The primary goal of product ergonomics is to offer the most user-friendly product possible to a largely unknown customer base. Therefore, developing such products requires understanding and incorporating the variability of human beings, both in terms of their anthropometric and cognitive characteristics, into the design. A current and emerging area of ​​research in product ergonomics is the scientific investigation of what constitutes the perception of comfort. Production ergonomics, on the other hand, focuses on creating human-centered workplaces in manufacturing and service companies. Here, the aim is to reduce employee strain while simultaneously optimizing productivity. In most cases, this involves addressing the question of what is reasonable and tolerable. Unlike product ergonomics, production ergonomics often involves knowing the employees and allowing for individualized attention to their needs. Since both product and production ergonomics employ the ergonomic methods described above, and since one manufacturer's "product" is often another's "tool," a precise separation between these two fields of application is practically impossible. Primary areas of application where systematic ergonomic development is currently pursued include aviation (specifically, aircraft cockpit design and radar controller workstation design), vehicle design (cars and trucks: cockpit design; anthropometric interior design, so-called packaging; design of new information systems intended to improve safety, comfort, and individual mobility), control room design (chemical plants, power plants; here, aspects of human reliability play a particularly important role), and office environments (design of monitors, office chairs, the overall arrangement of computer workstation elements, and software ergonomics). Another specialized area of ​​ergonomics is the research into limit values ​​for work under extreme conditions such as extreme spatial confinement, cold, heat, overpressure, extreme accelerations, weightlessness, disaster relief, etc.