Use Error

Dr.-Ing. Marcus JenkeSenior Human Factors Engineer | Managing Partner
Last updated: October 2026
Short definition

Ergonomics is, according to the International Ergonomics Association (IEA), the scientific discipline concerned with understanding the interactions among humans and other elements of a system, and at the same time the profession that applies theory, principles, data, and methods to design in order to optimize human well-being and overall system performance.

In medical technology, it provides the scientific foundation for products that can be operated safely, with low strain, and reliably.

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Definition and classification

The subject of ergonomics is neither the human nor the product in isolation, but the system formed by both: humans, equipment, task, and environment interact in ways that can be described and measured. The methodological standard of the discipline follows from this systems perspective. Ergonomic statements rest on body dimensions, forces, perception thresholds, measures of strain, and observed use behavior, not on the design instincts of individual project members. It is precisely this difference between a reasoned assumption and verifiable evidence that decides whether an ergonomic assessment holds up in technical documentation.

Internationally, the terms "ergonomics" and "human factors" are used largely synonymously; the International Ergonomics Association (IEA) explicitly treats them as equivalent in its definition. In German usage, by contrast, a narrowing has become established: Ergonomie (ergonomics) is often associated with the physical aspects of design, while human factors engineering (HFE) stands for the cognitive and organizational parts. Technically this separation is untenable, but it explains why both terms often appear side by side in projects and why responsibilities between mechanical design and the usability team regularly remain blurred.

The three domains of ergonomics

Ergonomics is traditionally divided into three domains that rarely occur in isolation in product development. A use error on an infusion device can have a cause in the arrangement of the keys (physical), in the design of the display (cognitive), and in the handover between two shifts (organizational) at the same time.

  • Physical ergonomics: body dimensions (anthropometry), biomechanics, posture, operating and holding forces, reach, repetitive loading, vibration, and weight. Typical questions in medical technology: Can a handpiece be held without fatigue for an entire treatment? Can a device be operated with gloves and with one hand?
  • Cognitive ergonomics: perception, attention, memory, decision making, and mental workload (see cognitive load). Typical questions: Is the device state unambiguous at a glance? Are alarms designed so that they can be distinguished by urgency without causing sensory overload?
  • Organizational ergonomics (also macroergonomics): workflows, communication, distribution of roles and tasks, shift and working-time models. Typical questions: How does a device configuration affect collaboration in the operating room team? Does a setting remain traceable across a shift change?

For medical devices, this three-way division is more than an academic ordering: It structures the search for causes. Anyone who explains an observed use error exclusively at the physical level regularly overlooks the cognitive or organizational cause that is actually effective.

Ergonomics, human factors, and usability engineering

In development projects, ergonomics, human factors engineering, and usability engineering are often used synonymously, although they play different roles. A practical distinction looks like this:

  • Ergonomics provides the scientific foundation: established knowledge about human capabilities, limits, and capacity, as well as the data and measurement methods with which these can be described.
  • Human factors engineering translates this knowledge into concrete design decisions for a specific product in a specific context of use.
  • Usability engineering is the normatively regulated process that documents, verifies, and validates these decisions in a traceable way and thus provides the regulatory evidence.

The result of this interplay is usability, which according to ISO 9241-11 is the extent to which a product can be used by specified users in a specified context of use effectively, efficiently, and with satisfaction. Ergonomics is thus not an alternative to usability engineering but its substantive basis, while usability engineering supplies the chain of evidence that a notified body (the independent conformity assessment body under EU medical device law) or a regulatory authority can review.

Ergonomics in medical device development

Medical devices pose special ergonomic requirements because they are rarely used under ideal conditions. A device that can be operated flawlessly in the lab can reach its limits in an ambulance, in a darkened operating room, in home use by a lay person, or under time pressure in an emergency. Ergonomic design therefore does not begin with the product but with the analysis of the real conditions of use.

Anthropometry and forces. Body dimensions vary considerably between sexes, age groups, and regions. In design practice, a range from the 5th to the 95th percentile of the target population is therefore usually covered, so that reach, grip sizes, and fields of view are usable for the large majority of intended users. Safety-relevant controls should be reachable across the entire range covered and operable with the forces realistically available, including with gloves, moist hands, or reduced hand strength.

Perceptibility. Displays, labels, and alarms must remain recognizable under the actual environmental conditions. Illuminance, viewing angle, viewing distance, contrast, and ambient noise are not side conditions but input variables of the design. In usability engineering, these factors are systematically captured as use environment factors.

Posture and sustained load. For products used over longer periods or many times a day, what matters is not one-time operability but cumulative load. Forced postures, repeated precision grips, or unfavorable weight distribution lead to fatigue, and fatigue increases the likelihood of use errors. Physical and cognitive ergonomics interlock directly at this point.

Interface to risk management. Ergonomic deficiencies are not purely matters of comfort. As soon as they can lead to a foreseeable use error that results in a hazardous situation, they belong in the use-related risk analysis (URRA) and thus in the risk management of the product.

Making ergonomics measurable: assessment methods

In practice, ergonomic assessments rarely fail for lack of expertise, but because they are phrased as opinions and provide no verifiable evidence. "The handle feels good in the hand" is not a statement that technical documentation can support. An assessment becomes robust only when it is based on collected data and linked to the real context of use.

  • Anthropometric analysis: comparison of grip dimensions, reach, and fields of view and operation with the body dimensions of the defined user groups.
  • Posture and load assessment: structured observation methods (such as RULA, REBA, or OWAS) for rating postures and loads during realistic use sequences.
  • Motion and force measurement: objective capture of movement sequences, joint angles, operating forces, and holding times as a data basis instead of an estimate.
  • Assessment of mental workload: established methods such as NASA-TLX or strain indicators to evaluate cognitive load in critical scenarios.
  • Observation of use in context: observation close to the context of real workflows, complemented by methods of task analysis and formative usability evaluation.

Only the combination of measurement data, structured expert assessment, and physiological or clinical interpretation makes ergonomic quality traceable: internally toward development and management, externally toward notified bodies and authorities.

Regulatory reference

In medical technology, ergonomics is not a voluntary quality aspiration but is anchored in regulation on several levels. The fundamental ergonomic principles and the general approach of the discipline are described in DIN EN ISO 26800 (international: ISO 26800) and, with regard to the design of work systems, in DIN EN ISO 6385 (international: ISO 6385). For the design of interactive systems, the series DIN EN ISO 9241 (international: ISO 9241), "Ergonomics of human-system interaction," is decisive; Part 11 defines the concept of usability, and Part 110 formulates interaction principles for dialogue design.

At the product level, the ergonomic requirement is operationalized through the usability engineering process according to IEC 62366-1; for medical electrical equipment, the collateral standard IEC 60601-1-6 refers to this process. The EU Medical Device Regulation (MDR) requires in Annex I that risks related to use errors be reduced, explicitly taking into account the ergonomic features of the device and the environment in which it is intended to be used. In its human factors guidance, the FDA takes a comparable approach in substance and treats users, use environment, and user interface as one connected system. Through the use-related risk analysis, the ergonomic assessment is finally interlinked with risk management according to ISO 14971.

In brief

Ergonomics is the scientific basis of user-centered design: It describes human capabilities, limits, and capacity and supplies the data with which design decisions can be justified. In medical technology it acts on three levels (physical, cognitive, and organizational) and is converted into verifiable evidence through the usability engineering process according to IEC 62366-1.

The decisive step in practice is the transition from opinion to measurement: Only reliable data make ergonomic quality traceable toward development, management, and the notified body.

Frequently asked questions (FAQ)

Is ergonomics relevant only for physical loads?

No. Ergonomics covers physical, cognitive, and organizational aspects. Perception, attention, decision making, and teamwork are part of it just as much as exertion of force or posture.

What is the difference between ergonomics and human factors?

Internationally, both terms are used largely synonymously. The International Ergonomics Association explicitly treats them as equivalent. In German usage, ergonomics is often related more narrowly to physical aspects, while human factors also includes cognitive and organizational parts. Technically this separation is not justified: Both terms denote the same discipline.

Which standards are relevant for ergonomics in medical technology?

Fundamental are DIN EN ISO 26800 (international: ISO 26800; general approach and principles of ergonomics) and DIN EN ISO 6385 (international: ISO 6385; design of work systems). For interactive systems, the series DIN EN ISO 9241 (international: ISO 9241) is decisive. At the product level, the ergonomic requirement is implemented through IEC 62366-1 and, for medical electrical equipment, through IEC 60601-1-6, embedded in risk management according to ISO 14971.

How can ergonomics be assessed objectively?

Through a combination of measurement and interpretation: anthropometric comparison, motion and force measurement, structured posture and load assessment, and methods for capturing mental workload. What matters is that the results are interpreted in the real context of use. Measured values alone do not replace expert assessment.

Is an ergonomic assessment sufficient to meet IEC 62366-1?

No. An ergonomic assessment provides important input information and design rationales but does not replace the complete usability engineering process with use specification, use-related risk analysis, formative evaluation, and summative evaluation. It is one building block of the chain of evidence, not a substitute for it.

Do you want to make the ergonomic quality of your product not just plausible but demonstrable? We combine measurement data, expert assessment, and medical interpretation into an objective ergonomics analysis.

More about our ergonomic analysis

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