Guidelines for working conditions when using a computer include:
A well-designed chair with easy-to-implement adjustability is essential. A user can vary angles of back support and the seat pan to control the degree of pressure on the thighs and back. Weight should be evenly distributed, with no extreme pressure points. An upright posture is a little easier to achieve if the seat pan is tilted slightly forward of horizontal. When a person is seated, feet should rest on the floor and the chair seat pan should be even with the back of the knee, ranging from 13 to 19 inches above the floor depending on an individual’s height. A foot rest may be used to relieve pressure on the thighs. Both lumbar and mid-level back support are needed. Arm rests, adjustable for height, are helpful to many people. The chair should have a five-point base for stability and casters for easy movement.
The keyboard provides the primary means of interacting with a computer. The keyboard should be in a comfortable position, and wrists should float over the keyboard when keying with a light touch so wrists and forearms remain straight. Although wrist pads are helpful for resting when not keying, they can actually create problems when a user keeps wrists on them when keying because the wrists can bend down. Different opinions exist on the appropriate angle of the keyboard; some people prefer a flat position while others find a reverse incline more comfortable. Split and curved keyboards are available, too. However, the most important part of keyboard use is keeping the wrists straight in line with the forearm and not bent to the side. When voice-recognition technology becomes commonly used, dependency on the keyboard will be reduced.
A mouse should be positioned next to the keyboard, reachable without extending the arm in an awkward position. Again, a light touch is needed and users should avoid gripping or squeezing the mouse. A wrist support or adjustable mouse platform may be helpful if a user begins to develop wrist problems. A variety of shapes are available for these pointing devices, and a trackball can be used for the same purpose.
A monitor should be directly in front of the user, with the top of the screen at or below the line of sight, 18 to 30 inches away from the eyes, and tiltable to avoid glare from overhead lighting and windows. If necessary, antiglare filters can be added. Screen size should be large enough for easy reading of screen character sizes with a screen refresh rate fast enough to avoid a visible flicker. An individual can experience blurred vision or fatigue from a poor monitor viewing angle, reflected glare, or a low-quality monitor. Because glands in the eyelids produce tears that cleanse eyes as the eyelids blink and the eyes move, irritated eyes can develop because one’s blink rate tends to decrease when one is concentrating.
Leonardo Da Vinci’s “Vitruvian Man” drawing (circa 1487) is based on correlations between ideal human proportions and geometry. Ergonomics is the scientific discipline concerned with the understanding of interactions among humans and other elements of a system.
Da Vinci’s image speaks to what is at the core of ergonomics …… human-centered design.