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Keyboard Primer

Keyboard Primer

Keyboards - An Ergonomic Primer – Outline
By David Gilkey, D.C., Ph.D, CPE
Director, Environmental & Radiological Health Sciences
Colorado State University

1)    Introduction

Keyboards remain the primary method for inputting data into computers.  It is presently estimated that 45 million American workers spend some time each day using a computer and keyboard.  Approximately 30 million workers use the computer and keyboard as their primary work equipment each day, all day, and up to 8 hours per day or more.  Keyboard use has been shown to be linked to several types of injuries known as “Upper Extremity Repetitive Stress Injuries” (UR-RSI's), “Cumulative Trauma Disorders” (CTDs), or “Work Related Musculoskeletal Disorders” (WRMSDs).  RSIs, CTDs, and WRMSDs are associated with the upper extremities (UE) or arms, forearms, wrists, hands, and fingers.  Common UE –RSI disorders associated with computer keyboard use include Carpal Tunnel Syndrome (CTS), Tendonitis, and Tenosynovitis effecting the hands, wrists, and forearms as well as Neck Tension Syndrome.  The Bureau of Labor and Statistics (BLS) reported that the incidence of such disorders has increased 770% between 1981 to 1991 (BNA, 1995).  Several studies have clearly shown a definitive link between UE-RSIs and keyboard use (NIOSH, 1997).  Ongoing research studies are aimed at determining exactly what role keyboard design and use play in the UE-RSI debate.  Ergonomics is the premier science which concerns itself with humans at work and the many aspects the “Human Computer Interface” (HCI).   Studies clearly demonstrate a scientific basis for ergonomic design of keyboards.   The following is an overview of ergonomic issues related to keyboards.

Definitions and Terms:

A)    Keyboards - Keyboards refer to the standard alphanumeric device for inputting data into computers.  Most keyboards measure roughly 18' long by 7" wide by 1-3" tall.  Pointing devices such as mice, trackballs, input pads are typically a different device, the exception being in many portable laptop computers where the pointing device is within or below the keyboard.

B)    Keyboard Performance – Performance criteria are usually based on comparing speed, error rate, fatigue, muscular strain, or other personal preferences.  Each user must decide what criterion is most important, this will help in the selection of the best keyboard for the desired purpose.  The data has not consistently shown that any type of keyboard is faster than its competitor to warrant a new design standard.  However, the data does support that users report less fatigue and muscular strain with ergonomically designed keyboards.  User comfort is a goal of the ergonomic design for the HCI.

C)    Keyboards as Part of a Workstation - The typical computer workstation includes the desk, display terminal, keyboard and tray, computer, mouse, chair, and a lighting source as well as other environmental factors.  The ergonomics of HCIs includes all aspects of interaction that can affect worker comfort and performance.   The relationship of the system components to human performance requires that all facets be optimized to maximize the HCI.  Keyboards are an important part of the HCI but must be viewed in the context of the entire work system and production goals.

D)    The Neutral Position – The neutral posture refers to the natural, least stressful, and most comfortable position of the body and limbs.  Neutral positions minimize energy demands, provide maximum stability of the musculoskeletal system, and will assure the least amount of stress on muscles, tendons, ligaments, bones, joints, discs, blood vessels, and nerves.  Neutral positioning can be achieved while sitting, standing, or lying down.  The neutral sitting HCI position is achieved with the body upright and supported, arms at the sides relaxed, elbows flexed near 900 and the hands and wrists pointed inward.  Non-neutral positions of the hand and wrist include ulnar and radial deviation, flexion, and extension.  Supination and pronation of the hands and wrists are non-neutral positions of the forearms.  Flexion and extension of the arms are non-neutral positions.  Non-neutral positions of the upper extremities result in stress, fatigue, and strain to muscles, tendons, ligaments, blood vessels, nerves, and joints.  Postural stressors are believed to be contributors to the development of UE-RSIs.  The standard keyboard does not facilitate neutral positioning of the UE during use.

E)    Split Keyboards – This refers to the separation of the keys on the keyboard into two halves or thirds to minimize the inward angle of the wrists and hands on the keyboard.  The standard keyboard does not separate alphanumeric characters to widen the contact surface thus resulting in a more constrained position for users.

F)    Detachable Keyboards – This refers to the separation of the keyboard from the computer.  This is the most popular design for today’s computers.

G)    Lateral Tilt – This refers to the angle or tilt of the hands from thumb to little finger.  For example, the ‘knife-edge’ of the hand and little finger tilts downward in a neutral posture. There is no tilt when the hands are flat at 00.  A standard keyboard is flat and does not tilt down and out. 

H)    Slope and Height – This refers to the angle of the keyboard from front to back and how much the keys are raised from a flat surface.  Most keyboards are designed to slope between 00 to 250 upward in the back.  Keyboard designers are also providing the newer negative sloped keyboards.  Most standard keyboards do have slope and height built into their design.

I)    Footprint – This refers to the overall size of the keyboard across the work surface.  The keyboard footprint is affected by the length and width of the design.   For example, portable laptop computers have a smaller footprint than the standard workstation keyboard seen in most offices.

J)    Keyboard Profile – This refers to the relative angles of the rows of keys on the keyboard.  The data supports multiple acceptable designs such as stepped, sloped, dished, and flat profiles.  Most standard keyboards have one of the profiles described.


K)    Key force and travel – This refers to the amount of pressure needed to depress the key and the distance traveled to activate the selection.  The standard keyboard requires 1 – 5 ounces of pressure and travels .05 to .25 inches.

L)    Tactile feedback – This is the sense of touch relating to key activation.  Our tactile sense is important in discerning how much force is needed to depress the key and the feel we get when we’ve achieved a complete activation.   What feedback from that keyboard tells us that the amount of pressure is adequate to reach the bottom of the down stroke?  Standard keyboards do provide features detected with the tactile sensors.

M)    Auditory Feedback – This would be the clicks, beeps, tomes, or other noises that tell us we have properly activated the keystroke.  Various keyboards make different noises as they are used. 

N)    Visual Feedback – This is the information on the display that gives us feedback that the right key has been hit.  This is important for the “two-finger” typist but not as important for the skilled touch typist. 

O)    Error Avoidance Features – These include rollover, hysteresis, interlocks, buffer length and repeat features.  These features allow rapid continuous typing without locking-up due to rapid data entry.  This allows the typist to exceed the speed of the visual feedback.  These design features must be evaluated in each keyboard.

P)    Programmability - Some ergonomic keyboards are programmable. This may be either onboard memory inside the keyboard, software for the computer, or both.  This feature allows users to customize the function of the keyboard.

3)    How Ergonomic Keyboards Address These Issues:

A)    The Neutral Position – Ergonomically designed keyboards facilitate a neutral or more neutral position of the UE to minimize stress on the hands, wrists, forearms, arms, neck and shoulders during keyboard use.  Ergonomic keyboards are aimed at increasing user comfort and maximizing the HCI while diminishing the potential for UE-RSIs.  Users report increased comfort, less fatigue, and fewer musculoskeletal complaints.  Neutral positioning is a fundamental concept of ergonomics. 

B)    Split Keyboards – Ergonomically designed keyboards integrate the spit-design through a number of approaches. The split keyboard achieves a more neutral posture of the UE thus minimizing stress on the tissues of hands, wrists, forearms, arms, and shoulders.  Specifically, the split design reduces ulnar deviation of the wrist.  Some ergonomic keyboards may have a curved face to achieve splitting or separating keys while others maintain the linear design and add space between sets of characters while others have detachable sides to achieve maximum separation to suit the user’s preference.

A)    Lateral Tilt – This feature also facilitates neutral or more neutral posture of the UE by allowing the hands and wrists to fall inward.   This diminishes stress to the UE soft tissues and minimizes RSI potential.  Specifically, this ergonomic design reduces pronation and ulnar deviation of the hand, wrist, and forearm.  The ergonomic keyboard is designed with a higher center and lower sides.  The amount of tilting varies from a slight 150 to 900 perpendicular to the tabletop.  Virtually all users can find their individual preference among the many ergonomic keyboards on the market today. 

B)    Footprint – The overall size of the keyboard must accommodate the electronic features necessary to complete the desired task.  Ergonomic keyboards attempt to minimize constrained postures while maximizing performance features of the equipment.  Small keyboards create a constrained HCI and will increase UE stress and injury potential.   Keyboards that are too large can also increase UE stress.  User preference and performance goals are the best criteria for selection.

C)    Detachable Keyboards – This ergonomic feature allows the best placement of the keyboard to facilitate optimal height adjustment.  Adjustable trays maximize the benefit of detachable keyboards.  This feature again adds to neutral posture goal and comfort of the optimal HCI.  This is the most popular design for today’s computers.

D)    Slope and Height – Ergonomic keyboards are designed to reduce wrist extension and diminish stress to the soft tissues of wrists while facilitating adequate finger reach to keys.  This design increases comfort to hands and wrists thus reducing fatigue and injury potential.  Most keyboards are designed to slope between 00 to 250 upward in the back.  Keyboard designers are also providing the newer negative sloped keyboards.  The negative sloped keyboard allows complete neutral posture of the wrist.  Some users believe this is the best design.  Negative sloping can also be achieved using an adjustable tray angled downward in the back.

E)    Keyboard Profile – This ergonomic feature allows the user to easily reach and activate the desired key.  This feature has been modified in ergonomic keyboards to minimize reach and reduce finger stress.  This ergonomic design addresses the functionality of the finger and hand for the comfort of user.

F)    Key force and travel – This ergonomic feature addresses the functionality and stress to the hands and fingers.   Ergonomic design keyboards minimize the stress and force necessary to depress or activate the desired key.   This reduces fatigues, discomfort, and injury potential.

G)    Tactile feedback – This ergonomic feature provides added sensory feedback to the user to properly gauge the amount of force necessary to activate the key.  Feedback is how our body judges the demands necessary to perform the job.  Ergonomic designs emphasize feedback to users for maximum control and monitoring with the least amount of effort.  Properly calibrated feedback minimizes stress while maximizing the HCI.
 
H)    Auditory Feedback – This ergonomic feature incorporates another sensory system, the ear, to gauge performance demands.  Sounds can help users know that they have properly activated the keystroke.

I)    Visual Feedback – The HCI system is intended to produce alphanumeric work product.  The end product is the best measure of overall performance on the job.  The visual feedback is assessed to gauge the quality of the work through error identification.  All computer systems provide this visual feedback to allow correction responses of users.

J)    Error Avoidance Features – These ergonomic features allow rapid continuous typing without locking-up due to rapid data entry.  This allows the skilled typist to exceed the speed of the display feedback.

K)    Programmability – This allows users to customize the function of the keyboard.  Ergonomic designs recommend minimizing repetitions to alleviate fatigue, breakdown, and injury.  Programmable features can reduce the numbers of times or distances reached to activate keys frequently used.  An example may be that, if someone doesn't like the fact that the shift key is typically closest to the bottom of the keyboard, a programmable key near the top can be used instead.  Other keyboards allow much greater depth and flexibility in programming. A single key can be programmed to take the place of dozen's of keystrokes, similar to macro's which are so common in spreadsheet programs.

Summary:

A)    The standard QWERTY keyboard layout was designed to slow users and keep them from jamming or locking the keys of the typewriter.  It was not designed to optimize human performance nor minimize the risk of injury to the UEs.  Electronic keyboards and the advent of computers have long exceeded the mechanical limitations of the typewriter.  Ergonomic scientists (Ergonomists) have been focusing their attention in recent decades on measuring parameters of the HCI to enhance human performance, optimize the interface, and reduce the stress and strain related to tissue breakdown and RSI development.  Significant gains have been made in the design of keyboards due to ergonomic influences.  Quality of life and preservation of worker health are paramount; ergonomics is committed to optimizing the HCI measures of speed, error, and overall production, but not at the expense of health integrity.  The fundamental construct that neutral posturing is better than unnatural postures is without challenge.  Injury development is a multifactorial event, which must be addressed on all possible levels.  Ergonomic interventions and designs are aimed at addressing products and processes on these levels. Keyboards must be evaluated in the context of the work system and the capabilities, limitations, and preferences of the individual user.

B)    Price - Ergonomic keyboards generally cost more than those without ergonomic features.  The number of features within the product, development costs, and manufacturing costs heavily affects keyboard pricing as well as quantity produced and market demand.   Unfortunately, the broadband use of ergonomic keyboards has not arrived.   Pre-packaged VDT workstations are not routinely equipped with ergonomically designed keyboards.  In most instances customers are looking to retrofit their workstations to optimize the HCI and minimize the risk for RSIs and CTDs or they are suffering the affects of poor ergonomics and are looking to reduce adverse health affects by improving the HCI through better ergonomics.

C)    Learning Curve - The message is simple, transitions take time, but stick with it and the benefits will far outweigh the initial frustration. The ergonomic keyboard can be used immediately; however performance aspects of speed, error, and overall productivity lag behind as the user becomes familiar and adept at using the new equipment.  The data indicates that the adaptive periods range from days to weeks.  Users, like all people, are creatures of habit; habits can be hard to change even when there are significant benefits derived. 

References

Bureau of National Affairs. (1995). 770 percent increase. Occupational Safety and Health Reporter, 36, p.1794.
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Helander, M. (Ed.). (1994). Handbook of Human-Computer Interaction. (4th ed.)  NY: North-Holland.
Honan, M., Sernia, E., Tal, R., Rampel,. D. Wrist Posture While Typing on a Standard and Split Keyboard. (1995). Proceedings of the Human Factors Society 39th Annual Meeting. Human Factors Society, 366-368.
IBM. (1991). Human Factors of Workstations with Visual Displays. (4th ed.) NY: IBM.
Lincoln, A., Vernick, J., Ogatis, S., Smith, G., Mitchell, C., Agnew, J. (2000). Interventions for the Primary Prevention of Work-Related Carpal Tunnel Syndrome. Journal of Preventive Medicine, 18, 37-50.
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National Institutes for Occupational Safety and Health. (1997). Musculoskeletal Disorders and Workplace Factors. NIOSH Pub No. 97-141.
Putz-Anderson, V. (1988). Cumulative Trauma Disorders: A Manual for Musculoskeletal Diseases of the Upper Limbs. NY: Taylor Francis.
Thompson, D. Thomas, J. Cone, J. Daponte, A. Markison, R. (1990). An Analysis of the TONY! Variable Geometry VDT Keyboard. Proceedings of the Human Factors Society 34th Annual Meeting. Human Factors Society, 365-369.
Swanson, N., Galinsky, T., Cole, L., Pan, C., Sauter, S. (1997). The Impact of Keyboard Design on Comfort and Productivity in the Text-Entry Task. Applied Ergonomics, 28, 9-16.