The word “Ergonomics” originates from two Greek words; ergos which means “work” and nomos which means “laws”. Ergonomics is the scientific discipline that deals with understanding the interaction of human beings and other elements of a system, and the profession that applies theory, principles, data and methods to design to optimize human well-being and overall system performance. Ergonomics basically works towards optimizing the interaction between the work environment and the worker. In this blog, I would be explaining anthropometry and its importance in the ergonomic design of products.
Anthropometry And Its Types
Anthropometry is defined as the systematic study of the physical properties of the human body. As a part of the anthropometric study, the three major human body parameters are measured. They are Size (e.g., height, weight, surface area, and volume), Structure (e.g., sitting vs. standing height, shoulder and hip width, arm/leg length, and neck circumference) and Composition (e.g., percentage of body fat, water content, and lean body mass). The above-measured parameters constitute the anthropometric data.
Anthropometry is classified into two types based on the motion of the human body being considered for measurement. They are:
- Static Anthropometry: The external body dimensions are measured when the person is placed in a rigid or a static position.
- Dynamic Anthropometry: The external body dimensions are measured with various movements taken under consideration.
Certain special tools with high accuracy are used to obtain the anthropometric data. They are as follows:
- Stadiometers: They are used to measure the height of the human body.
- Anthropometers: They are used to measure the length and circumference of body segments.
- Biocondylar callipers: They are used to measure the diameter of the bone.
- Skinfold callipers: They are used to measure skin thickness and subcutaneous fat.
- Scales: They are used to measure the weight of the body.
The Development Of Anthropometry
The ancient civilizations of Rome, Greece, and Egypt used anthropometric measurements for the artwork to portray the beauty, power, and other desirable attributes of the human form. The artists during the renaissance applied anthropometric measurements to artistic works by applying human proportions. The Vitruvian Man is considered one of da Vinci’s greatest works. He obtained measurements of the human body by analyzing cadavers.
In the year 1880, Alphonse Bertillon was the chief of criminal identification for the Paris police. During his tenure working for the Paris police force in the criminal records department, he found it was becoming increasingly more difficult to identify repeat offenders. The criminal records were stored alphabetically and many criminals were successful in devising aliases to avoid deportation and harsher sentences. He joined hands with his younger brother Jacques Bertillon to find a solution to this problem. Jacques Bertillon was a French statistician and demographer.
To solve this problem, Alphonse Bertillon and his younger brother came up with a new classification system based on anthropomorphic measurements. The basic assumption of this classification was that the bone density is fixed past the age of 20 years, and human dimensions are intrinsically highly variable. He obtained the measurements of height, breadth, foot size, length and width of the head, length of the middle finger, and the length of the left forearm, as well as other morphological and distinguishing characteristics of criminals in custody. From the above measurements, he classified each criminal into small, medium, or large and he also included frontal and profile photography in each file. This type of photography is till date used and its called “Mug Shot”. The Paris police were impressed with Alphonse Bertillon’s solution and it was implemented to quickly and easily identify unknown individuals and repeat offenders. The use of this anthropometric system spread to other countries all across the globe. Alphonse Bertillon is known as “The Father Of Anthropometrics”.
The Bertillon System was later replaced by fingerprinting as the primary method of identification. A solution that was meant to distinguish between repeat offenders and unknown individuals is now being used in industrial design, clothing design, ergonomics and architecture where statistical data about the distribution of body dimensions in the population are used to optimize the product.
Principles Involved In Using Anthropometric Data For Ergonomic Product Design
Anthropometry is important in several fields such as industrial design, architecture, interior design, and furniture products. In the above-cited domains, the human body dimension data is needed to produce optional and ergonomic products. When applying anthropometric data for ergonomic and optimal product design, there are four basic principles. They are:
1.Design for the Average: This principle is used in the determination of the minimum size of the width and height of the emergency door.
2.Design for Adjustability: This principle is used in the design of a car seat that can be moved forward or backwards, and the angle of the backrest can be changed.
3.Design for Extremes: This principle is used to determine the minimum size of the width and height of the emergency door.
4.Design for Individual: This principle is used for designing a spacesuit for an individual.
Design Method Using Anthropometry
The following methods are involved in designing products using anthropometry. They are as follows:
- Determine the design needs
- Determine and describe the users’ population
- Sample size selection that will be considered for the product design
- Determine the body dimensions that will be used
- Determine the principle involved in the anthropometric data for the product design and the percentile considered
- Prepare the measurement tools
- Data acquisition
- Data processing
Applications Of Anthropometry In Ergonomics
Today, ergonomics professionals apply the principles of understanding human factors to the design of equipment, systems and working methods to improve comfort, health, safety, and productivity. This includes physical ergonomics, cognitive ergonomics, organizational ergonomics, environmental ergonomics, visual ergonomics and other types of ergonomics.
Measurements like eye height, the distance from the floor to a person’s eyes, can be taken sitting or standing. Other measurements include elbow height, hip breadth, overall stature, knuckle height, and popliteal height, or the distance from the floor to the back of the knee. These measurements play an important role in the design of architecture, furniture, tools, cars, clothes and more to fit the human body.
Anthropometry is used in ergonomics to optimize the fit and function of products, both during design and during evaluation. When evaluating the fit of a chair for a person, different leg segments are considered to optimize the height and depth of the seat pan. When determining the appropriate height of the work surface we take into account both elbow height and knee height. Measurements of the hand like breadth and length are used when evaluating the grip of a hammer or the fit of a computer mouse.
Limitations of Anthropometry
Anthropometric data has an important role in the design of optimal and ergonomic products. There are some limitations of the Anthropometric data which a designer or an architect must remember while developing their products and structures respectively. They are as follows:
- The anthropometric data always needs to be revised. The world is growing at a dynamic pace. The anthropometric data considered a decade ago might not be relevant today.
- There is a lack of standardization of the anthropometric data. The anthropometric data from the United States of America would not be useful for designing ergonomic products for a country like India. On a similar note, the anthropometric data from India would not be useful for designing products for the United States of America.
- The arcs of motion of the human body are not considered in the anthropometric measurements.
- The anthropometric data must be considered with a diverse group of people with different characteristics and abilities. By considering a diverse group of people with different characteristics and abilities can help in the development of ergonomic products.
- The statistical range cut-off range for the anthropometric data is at times quite random. It's not always guaranteed that the chosen cut-off would cater to everyone using the product.
- Inter-observer errors during the measurement of the anthropometric data can prove costly in designing the product as it involves a statistical approach of obtaining the cut-off and percentile is used.