1.1c Physiological Factors
Essential idea
Designers consider three human factors to ensure products meet ergonomic needs.
Nature and Aims of Design
Nature of design:
Designers study physical characteristics to optimize the user’s safety, health, comfort and performance. (1.5, 1.18, 1.20, 2.9)
Aims:
Aim 8: Understanding complex biomechanics and designing products to enable full functionality of body parts can return independence and personal and social well-being to an individual.
Guidance
Types of physiological factor data available to designers and how they are collected
How data related to comfort and fatigue informs design decisions
The importance of biomechanics to the design of different products considering muscle strength, age, user interface and torque
Summmary
Designers analyze physical characteristics to optimize user safety, health, comfort, and performance
Comfort is an important consideration for designers as it influences the way users interact with products
Designers should consider biomechanics to develop an inclusive design that takes into account the physical abilities, strength, and movement of the user.
Consider the following questions:
What are some physiological factors that designers collect data on to optimize user safety and performance?
How can designers reduce the risk of Musculoskeletal disorders (MSDs) in their designs?
What is an example of an application of task analysis using AI and ergonomics?
How does the consideration of comfort in product design relate to your own experiences with using products? Are there any products that you find particularly comfortable or uncomfortable? Why do you think that is?
Think about a task or activity that you frequently perform. How might the principles of biomechanics and ergonomics be applied to improve your performance and reduce the risk of injury or strain? What changes could you make to your posture, movements, or equipment to optimize your performance and reduce fatigue?
Consider the impact of prolonged use of technology on your own body. How might designers use data on physiological factors to optimize the safety, health, and comfort of users? Are there any changes that you could make to your own technology use to reduce the risk of musculoskeletal disorders or other health issues?
Concepts and Principles
Physiological Factors
Physiological factors encompass the physical aspect of the body. Designers use a range of physiological data to inform their design decisions. Some physiological factors that they may consider are:
Muscle strength in different positions: How strong a muscle is in different positions.
Endurance in different positions (how long a position can be maintained before discomfort sets in)
Visual acuity (how well the user can see under different conditions)
Tolerance to hot or cold temperatures
Range of frequencies that can be heard by humans
Hand/eye coordination
Comfort and Fatigue
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 stresses on the body. Designers need to collect data to inform their design decisions.
Comfort
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 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.
Tool handle design can influence comfort and fatigue. The ideal diameter is dependent on a number of variables.
Resources:
Patkin, M. (2001). A checklist for handle design; A detailed survey of factors and considerations when designing handles
Hand Tool Design Considerations: Canadian Centre for Occupational Health and Safety; description and comparison of design factors for handheld power tools
Wang, Ching-Yi, and Deng-Chuan Cai. “Hand Tool Handle Design Based on Hand Measurements.” MATEC Web of Conferences, vol. 119, 2017, p. 01044., doi:10.1051/matecconf/201711901044 ; Analysis of hand tool measurements. Some good information about how to do a study and present data.
Fatigue
a feeling of tiredness or weakness; happens 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) which 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.
Symptoms of MDS
Biomechanics
Biomechanics is the study 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 a inclusive design that takes into the physical abilities, strength, and movement of the user; and,
Avoid harming the user through 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 20's, for example
Repetition
How frequently a task is repeated. Task 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 that 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.
Task Analysis us Artificial Intelligence (AI)
An interesting application of task analysis using AI and ergonomics is software developed by Soter Analytics. The software analyses video of a user doing a task and maps the movement of joints. A risk analysis can be done by looking at the movements and identifying if they are unhealthy or risky (can cause injury). The red lines indicate a movement that is outside what is considered a safe parameter or range.
Learn more about the process here.