Physiology in design is the study of how the human body functions and responds when interacting with a product, system, or environment. Designers apply physiological data about visual accuracy, fatigue, and muscle control to improve safety, comfort, efficiency, and usability.
Within A1.1 Ergonomics, physiology helps designers match a design to users' functional capabilities and limitations. It differs from anthropometrics, which concerns measurable body dimensions such as hand breadth or standing height.
| Physiological factor | Meaning and design implications |
|---|---|
| Visual accuracy | The ability to see and distinguish information correctly. Legible typefaces, suitable text size, strong contrast, appropriate lighting, and correct viewing distance reduce reading errors. For example, a control panel should not rely on small, low-contrast labels. |
| Fatigue | A reduction in physical or mental performance after prolonged activity. Repetitive movements, sustained force, poor posture, vibration, or continuous screen use can cause muscular or visual fatigue. Adjustable seating, task variation, supportive handles, and reduced operating force can limit it. |
| Muscle control | The ability to coordinate muscular movement accurately. Fine motor control supports precise actions such as selecting a small touchscreen icon, while gross motor control supports larger actions such as operating a lever. Control size, spacing, resistance, and feedback should match the intended user. |
These factors interact. As fatigue increases, muscle control and visual performance may decline, increasing errors and accident risk. A well-designed handheld tool might therefore use a non-slip grip, balanced mass, low trigger force, and clear markings so that it remains controllable during extended use.
A common misconception is that physiology is simply another term for body size. Body size is primarily anthropometric; physiology concerns body functions and responses, although both contribute to ergonomic design.
Exam technique: When asked to explain a physiological factor, define it, identify the relevant user limitation, and show how one specific design feature responds to it. Avoid merely stating that a product is “comfortable”; explain the physiological mechanism and its effect on performance, safety, or usability.