A1.1 / Ergonomics

Guiding question:

How do ergonomic considerations influence the design of a product?

1.1.1 - Ergonomics is the relationship and interaction between people (aspects of the human body) and the products, systems and environments they use.

We take ergonomics and human factors to mean the same thing. One of the two terms may be used more in certain contexts or sectors. For example, 'ergonomics' tends to be used more regarding furnishing and 'human factors' in the healthcare, defence and energy sectors. Ergonomics and human factors include numerous different physiological, psychological, behavioural and environmental aspects (factors) that need to be understood in order to design products and systems that users can interact with comfortably. In general terms, human factors (or ergonomics) aim to improve:

Ease of use
Operational comfort (Reduce stress and fatigue)
Performance and reliability (Reduce human error)
Safety
Ease of maintenance

Physical Ergonomics

This focuses on the physical interaction between humans and the environment, including:

Anthropometry: This involves understanding the physical dimensions and capabilities of the human body, such as body size, strength, and range of motion.
Biomechanics: This studies the forces and movements acting on the body, ensuring that tasks and equipment are designed to minimize physical strain and fatigue.
Environmental factors: This includes considerations like lighting, noise, temperature, and air quality, which can significantly impact physical well-being and performance.

Cognitive Ergonomics

This area explores the mental and psychological aspects of human-system interaction, encompassing:

Perception: This involves how humans interpret information from their senses, including visual, auditory, and haptic feedback.
Attention and memory: Understanding how humans process and retain information is crucial for designing clear and efficient user interfaces.
Mental workload: This involves the amount of cognitive effort required to complete a task, ensuring users are not overloaded and can perform effectively.
Decision-making: Designers need to consider how users make choices and understand their cognitive biases to create intuitive and predictable systems.

Organizational Ergonomics

This focuses on the broader social and organizational context in which human-system interaction occurs, including:

Job design: This involves structuring tasks and roles to optimize performance, satisfaction, and well-being.
Workforce management: This includes factors like training, competence, communication, and leadership, which directly impact how humans interact with systems and each other.
Organizational culture: The values, beliefs, and norms within an organization can significantly influence how work is done and how effectively humans interact with technology.

1.1.2 - Anthropometrics involves the measurement of human physical dimensions expressed in the percentile range. This method specifically focuses on determining and presenting the range of individuals’ physical characteristics.

In 1955, Industrial designer Henry Dreyfuss wrote Designing for People, an autobiography that detailed his principles of anthropometrics. This book was followed by The Measure of Man in 1959. The Dreyfuss work codifies the field of human factors by introducing “Joe” and “Josephine”, an average pair given anthropometric charts of their lives from infancy through old age.

Anthropometry (from the Greek word “Anthropos” meaning “man” and “metron” meaning “measure”) is an aspect of ergonomics that deals with body measurements, particularly the areas of size, strength and capacity. Anthropometry provides statistical data about the human body in particular user populations. This data can be used to design products that are comfortable and efficient to use. A wide range of anthropometric data is available in the form of diagrams and data tables.

A designer must work with data appropriate to the target market of the product or system they are designing for. Designers will need to consider which group will interact with the product or service to use the appropriate data group. Factors such as age, gender and ethnicity influence anthropometric measurements. Because of this, designers must carefully consider whether the data set they intend to use, is in fact representative of the users of their product. Human dimensions are also not always in proportion. Just because a person is tall, does not necessarily mean that the rest of their body will be in proportion. For example, a tall person can have short arms, which means for instance their reach might be smaller than expected.

How would you classify yourself anthropometrically?

Anthropometric data can be categorized into two types of data:

Static (structural) anthropometric data - measurements when the body is in a fixed position and considers measurements such as:
- Skeletal dimensions: measurements of the length of bones between joint centres.
- Static or stationary physical measurements: weight, height, ear size.
- Soft tissue measurement: muscle, fat, skin etc.
Dynamic (functional) anthropometric data - measurements in motion such as:
- Kinoshere or reach (could be arm plus extended torso or without extending limbs).
- Grip strength.
- Reaction times.
- Clearance (two people moving through a doorway).

The images above show examples of static and dynamic anthropometric data. What picture shows what type of data?

In a lot of the illustrations above, there are representations of humans taken from an orthographic view ( 2D front, side or plan elevation). These 2D-scaled physical anthropometric models are based on a specific percentile and are called ergonomes. Often they are plastic or card manikins ‘hinged’ at the major joints to allow a variety of positions which allows a designer to check standing and seating positions.

Ergonomes are used with drawings of the same scale as the model to consider the relationship between the size of an object and people. They are also used to model for instance view, field of reach, field of vision, etc.

Examples of manakins

A manikin is an anatomical 3D model of the human body. Full-scale manikins are generally more expensive than ergonomes and they give a better representation of the overall ergonomics in the design context (such as crash test dummies).

In order to find reliable anthropometric data, designers and manufacturers can make use of primary and/or secondary data.

Primary data results from research that a designer or manufacturer conducts firsthand. The benefit of doing firsthand research is that a sample of a user population can be chosen that matches well with the intended end-users of a product. On the other hand primary research, unless backed by a larger organization, often can only consider a relatively small number of samples and consider only a small range of measurements. If you have a particular client or access to the user population you wish to design for, you may wish to collect measurements yourself and generate your own primary data.

Secondary data are existing research results collected by others. Designers and manufacturers have access to large databases (in print and online) of anthropometric measurements developed by branch organizations, government agencies and regulatory bodies. The use of secondary anthropometric data may save time and/or cost for a designer or a manufacturer. It may however also be outdated, unreliable or not fully compatible with the specific target audience for which a product is intended.

Anthropometric data is actually usually presented to designers in the form of data tables (either online or in books). Note that in the table below the sample for this particular user population is 383 male junior rowers. The data therefore might seem reliable, but when you are a designer of rowing boats for the Japanese national team, you might have to be careful using this data from the US in the 1970s!

Static anthropometric data is collected using standardized equipment such as stadiometers or anthropometers, sliding callipers, skinfold callipers, fabric tapes etc. It can sometimes be difficult to accurately collect anthropometric data mainly due to limitations on:

Tools used: unreliability of the actual tools and the calibration and maintenance of the tools.
Personnel training: The accuracy and consistency of where measurements are taken on the subjects is directly linked to the level of training of the people taking the measurements.
Time of the day: because the cartilaginous disc in the spine gets compressed by body weight throughout the day. We can be up to 2.2mm shorter in the evening.
Subjects' body shape: Due to the physical size or shape of some of the subjects it may be difficult to collect measurements from a defined specific area.
User does not carry out tasks in the same way: subjects are human and move dynamically and are not always compliant.

What sources of anthropometric data can we find (online)? What types of organizations produce this data? Why?

1.1.3 Percentiles aid in the selection of appropriate anthropometric data to satisfy the majority of a user population.

Anthropometric data can be plotted on graphs or presented in tables. The percentile graph to the left shows how the distribution of height for a user population varies. To the left of the average, there is a point known as the 5th percentile, because 5% of the people (or 1 person in 20) are shorter than this particular height. The same distance to the right is a point known as the 95th percentile, where only 1 person in 20 is taller than this height.

The graph shows a population with equal distribution. The graph is symmetrical – so that 50% of people are of average height or taller, and 50% are of average height or smaller. But in most populations, the 50th%'ile will be skewed toward either the lower end or higher end. Note how the mean is not always at the frequency maximum.

If for example, the distribution curve of all people in a primary school were studied for height, there would be many small children as well as adults. The curve would be “skewed” towards the “shorter” end. So aiming a product at this particular group would need a detailed study of the anthropometric data.

What other anthropometric data might there be that does not follow a equal distribution?

Sometimes a designer can’t accommodate all the users of a product because there are conflicting solutions for a design. In this case, a judgement will have to be made on what is the most essential feature.

You should probably not compromise on features related to safety: if there is any real risk of injury, you may have to use more extreme percentile ranges (method of extremes) in your design (2.5th or 97.5th) to ensure everyone is protected, not just 95% of people.

Multivariate accommodation (fitting in several variables, for example, in a car you need to fit in terms of sitting height, leg room, arms reach, viewing angles, hip breadth, thigh length) means that accepting 5% being designed out for each important dimension is not viable, because different people will be designed out for each variable. People have different proportions. Those designed out because they are too short may not be the same as those designed out because their arm reach is too short.

What antropometric data do you need to consider for your design project? [link]

1.1.4 - To ensure products are appropriate to a range of percentiles, we choose to design products to be adjustable and/or be produced in a range of sizes.

In order to accommodate a wide range of users, products often come in a range of sizes or allow adjustability. Clothes for instance come in a range of sizes to accommodate different percentile ranges. Desk chairs are adjustable in height. Backpack straps can be adjusted for a better fit around the shoulders. Bicycles use a combination of a range of sizes to suit different heights or riders as well as adjustability of for instance the height of the seat and handlebars.

1.1.5 - In design, consideration must be given to work envelopes, reach, clearance, adjustability and range of sizes.

Clearance can be defined as the minimum distance required to enable a user into or through an area. This is for instance important when designing emergency exits and safety hatches. Some examples of clearance need definitions:

The minimum vertical space between the floor and an overhead obstruction must allow for the tallest user plus their footwear and PPE gear.
The minimum horizontal space between obstructions must allow for the widest plus room for movement and equipment - think of wheelchair users.
An unprotected hazard must be out of reach for the user with the longest arm length - think of guards on large machine presses.
Grill opening must not be wide enough to get your fingers in.

Reach is also known as the workspace envelope. A 'workspace envelope' is a 3-dimensional space within which you carry out physical work activities when you are at a fixed location. Workspace envelopes should be designed for the 5th percentile of the user population, which means that 95% of users will be able to reach everything placed within the envelope.

Many products tend to be available in different sizes or with adjustability built in when there really is no ‘one size fits most’. The 5th to 95th percentile range of a population group should be considered for adjustability, as manufacturing for the more extreme groups can be expensive and create manufacturing difficulties. Other accommodations, such as add ons or extensions could be provided for these groups of outliers.

1.1.6 - Physiology is the study of systems and biomechanics within the human body, their responses, limitations and capabilities.

Definition of idealized gripping gesture proposed by ISO 8727 and further elaborated on in an anthropometric study of hand tool handle design

This manual material handling analysis online tool by an insurance company provides both the male and female population percentages capable of performing manual material handling tasks without perceived overexertion.

Designers study physical characteristics to optimize the user’s safety, health, comfort and performance. Physiological ergonomics deals with the physical load on the human body when performing tasks using a product or system. It aims to reduce repetitive stress injuries, prevent musculoskeletal disorders and, more in general, to improve health safety and the physical operational comfort of products.

Physiological factor data can be used in many ways to develop new products or improve existing designs. This data is collected to evaluate and optimise human safety, health, comfort and performance. Examples of physiological factor data are:

Range of motion
Hand/eye coordination
Strength
Size
Stamina - muscular strength or endurance in different positions
Visual sensitivity - to light
Tolerance to extremes of temperature
Frequency and range of human hearing
Body tolerances - how much the body can withstand when using or working with a product.

Physiological data can be collected through performance tests, user trials and the synthesis of anthropometric data.

When people use a product they can put strain and stress on their body. Sitting for long periods of time, or being required to turn a handle put stress on the body. Designers need to collect data to inform their design decisions.

Comfort (in the context of this subtopic) is being free of physical pain. Comfort is an important consideration for designers simply because it influences the way users interact with products. Perceptions of comfort vary from person to person. A good example of this is the difference in preferences for sleeping mattresses. Some people will prefer a very firm or hard mattress, while others a soft and cushiony one.

Considerations for designers

Adjustability: For designers, being aware of these different preferences could influence how they incorporate adjustability into their designs. Users could choose to adjust the product (i.e. the softness of the chair) or select options that address their preferences (i.e. choosing a firm over a soft mattress).
Pleasure: Comfortable products are pleasurable to use. Focusing on the comfort will increase user acceptance of a product. If something is not comfortable to touch, users will not want to interact with it.

Fatigue is a feeling of tiredness or weakness happening over time. Because fatigue happens over time, it is important for designers to consider the impact of prolonged use of their designs on the human body. Fatigue can also lead to Musculoskeletal disorders (MSDs) in the muscles, nerves, blood vessels, ligaments and tendons. Risk factors can include:

lifting heavy items
bending
reaching overhead
pushing and pulling heavy loads
working in awkward body postures
performing the same or similar tasks repetitively

Fatigue can also affect decision-making and performance. In short, you are simply too tired to perform at your best. Considerations for designers:

Performance: Designs should reduce fatigue as much as possible, and enable the user to perform at an expected level for as long as possible.
Health and Safety: Fatigued users are more likely to injure themselves or other. In addition, injuries can be permanent, or cause chronic (consistent) pain.

A poorly designed tool handle may encourage the user to hold it or use it in a manner that is unsafe or harmful.

Safe Lifting Weights according to the Health and Safety Executive in the UK.

Biomechanics relates to the mechanism of living things (how they move). Biomechanics includes research into the operation of muscles, joints and tendons, force, repetition, duration and posture.

Understanding how humans move and interact with products in different situations has always been an important part of the design process. With the advent of modern technology and especially with the advancements in motion capture technology, how designers and design teams can access and analyse this data has dramatically improved.

Biomechanics is the study of the mechanical movements of our body. It focuses on how our body moves and how it is affected by different forces.

For designers, understanding the range and ability of the human body can help us design products that can comfortably, safely, and efficiently meet the needs of users. Designers should consider biomechanics for two reasons:

Develop an inclusive design that takes into the physical abilities, strength, and movement of the user; and,
Avoid harming the user by increasing the risk of musculoskeletal disorders (MSD)

To achieve this, designers should consider these four factors below:

Force - The amount of compression, pushing, twisting, pulling, etc., that a person can exert. It is directly related to muscle strength. Designers should consider the amount of force required to do an action (turn a knob, tighten a lid, pull a zipper, squeeze a handle, etc.). It is also important to consider the user group and how much force the typical user is able to exert: Young children and the elderly have lower muscle strength than some in their 20s, for example
Repetition - How frequently a task is repeated. Tasks that are repeated at a high frequency can impact the body in a negative way. Designers should consider how frequently a task needs to be done, and in most cases, reduce the frequency and intensity of the task as much as possible. For example, workers at a workstation may develop musculoskeletal disorders if they are required to repeat a task over and over again. The ergonomics of workstations should reduce this risk as much as possible.
Posture - The position the body is in, whether standing, sitting, or lying down. Designers should consider the posture the user takes when performing the task. It is important to minimize physical stress on the body, while also allowing the body to be supported appropriately. when designing a computer workstation chair, the designer would need to consider the seated posture of the user which also allows them to type comfortably.
Duration - How long the task is performed or repeated. Designers should consider duration along with frequency. Even small durations, repeated many times, can damage human tissue.

Symptoms of MDS - Source: Occupational Health Clinics for Ontario Workers

1.1.7 - Psychology is concerned with the study of the human mind and involves the study of all the human senses that may be involved in sending information to the brain.

Cognitive ergonomics is concerned with mental processes such as perception, memory, reasoning and motor responses as they affect the interactions between humans and a product or system. Understanding psychological factors can greatly improve the quality of user-product interfaces. It may lead to better:

Affordance - How well does a product or system make clear how it can or should be used? How intuitive is a product to use?
Constraints - How well does a product or system restrict or avoid misuse?
Mapping - How logical is the causality between a control and the action it triggers?
Causality - Does the product or system provide feedback after interaction? How does the user know their action was successful (or not)?
Conventions - How are affordance, constraints, mapping and causality understood across different groups of humans (cultures, age groups, etc.)?

Psychological factor data sometimes result from simple measurements of physical properties like sound levels, brightness of light and temperature, but can also be attempts to measure much more complex cognitive states such as comfort or value.

Focus: What does a user pay attention to, over time, when interacting with a product or system.

Smell is important in food, perfumes, candles and chemicals. Unpleasant odours are added to chemicals to warn people.

Taste: Responses to taste are often a factor of culture and experience. Important for young children’s products who explore the world with their mouths. In molecular gastronomy, chefs often try to surprise by mismatching visual and taste experiences.

Comfort: The feeling of being well-supported and safe can be a physical and/or emotional response to a product. This may be an objective or subjective human factor.

Light: the level of illumination should increase as tasks become more precise (surgery vs dining room). Fluorescent lighting in the workplace can cause eyestrain and visual fatigue due to flickering. Flickering can also be dangerous when operating rotating parts on machinery. Light has an effect on ambience and mood.

Sound: can be used to provide information such as warning signals (fire alarm or alarm). It can be used for reassurance that the product is working (ticking watch, whistling kettles, reversing trucks). It can improve or enhance the experience (playing music in an exhibition). Noise can also be negative in a workspace (open-plan offices use screens to reduce noise).

Value is perceived as a function of cost, features, prestige, rarity etc. or a combination of these factors.

Texture: Shapes and textures improve products and make them easier to use, for example, bottle tops, handles fabrics and non-slip floors, smooth worktops in the kitchen.

Temperature: A range of comfort zones will exist based on body mass, manner of (safety) )dress or even physiological changes that can be developed from exposure to a particular temperature or environment over time.

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