Ergonomics

Notes

Study Notes

HCI Notes: Ergonomics

Focus: HCI Ergonomics

The study of human factors in the design of interactive systems and environments.

1. What is Ergonomics?

Ergonomics (or Human Factors) is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system. Its goal is to optimize **human well-being** and **overall system performance**.

  • **Core Focus in HCI:** The physical relationship between the user, the hardware (keyboard, mouse, screen), and the working environment.
  • **Goal:** To design systems that fit the human user, rather than forcing the user to adapt to the system.

2. Physical Ergonomics: The Workstation

Achieving a neutral, stress-free working posture is the primary objective of workstation ergonomics.

Display Setup

  • **Height:** Top of the screen should be at or slightly below eye level.
  • **Distance:** Approximately arm's length (50-70 cm).
  • **Glar:** Avoid reflections and use anti-glare screens.

Seating and Posture

  • **Chair:** Must be adjustable (height, back support, armrests).
  • **Back:** Should be straight, fully supported, and slightly reclined (100°-110°).
  • **Feet:** Must be flat on the floor or supported by a footrest.

Input Devices

  • **Keyboard:** Positioned so forearms are parallel to the floor; use a negative tilt for neutral wrist position.
  • **Mouse:** Should be close to the keyboard; use vertical or trackball mice to reduce wrist extension.

3. Health Issues and Prevention

Repetitive Strain Injury (RSI)

A general term for various conditions caused by repeated physical movements, often resulting in pain and damage to muscles, tendons, and nerves.

  • **Key Example:** **Carpal Tunnel Syndrome** (affecting the wrist/hand).
  • **Prevention:** Use ergonomic input devices and maintain proper wrist alignment.

Visual Fatigue (CVS)

**Computer Vision Syndrome** (CVS) includes symptoms like dry eyes, headaches, and blurred vision due to prolonged screen use.

  • **Prevention:** Follow the **20-20-20 Rule** (every 20 minutes, look at something 20 feet away for 20 seconds).
  • **Software Factor:** Ensure high-quality fonts, anti-aliasing, and appropriate contrast settings.

4. Environmental Factors

The surrounding environment plays a large role in comfort and cognitive performance.

A. Lighting

  • **Avoid Glare:** Screens should be positioned perpendicular to windows or light sources.
  • **Task vs. Ambient:** Adequate general room light, but task lighting (e.g., desk lamp) should be adjustable and focused where needed.

B. Noise and Thermal Conditions

  • **Noise:** Should be kept low, as excessive noise increases stress and interrupts concentration (especially cognitive tasks).
  • **Temperature:** Thermal comfort (usually around $20^\circ \text{C}$ to $24^\circ \text{C}$) is critical, as extreme temperatures reduce performance and increase fatigue.

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