Cornell University Ergonomics Web

DEA 3250/6510 CLASS NOTES

KEYBOARD DESIGN

KEYBOARDS

Brief History of Keyboard design:

• 1868 - Sholes typewriter invented which had the paper facing down as the person typed. First commercial typewriter to have any success.
• "QWERTY" arrangement developed to minimize mechanical "jams" and thereby improve system performance. Became standard layout after 1870's competition to see who could type the fastest (person in the contest was a touch-typist).
• Original Mechanical typewriter had flat keys arranged in a stepped design - typists trained to keep wrists NEUTRAL (like pianists)
• With electronic keyboards the size of the keyboard is reduced and the key orientation is changed compared with a mechanical typewriter

Recommended keyboard worksurface height for typewriters was the 26" typing return (plus the height of the keyboard). At this height shoulder muscle tension was lessened, and the keys were stepped so that wrists could remain flat and neutral.
As hands go into typing position, hands have a tendency to go into ulnar deviation, especially with a wide person. First split keyboard design is often attributed to Klockenberg (1926  in Germany), but actually a split keyboard was used in a typewriter built in1886 (Louis Crandall, Syracuse, NY). Etienne Grandjean (Swiss ergonomist) developed a split keyboard in 1976 which supported the whole forearm (curved keys as well).  Split keyboard - assumption is that the problem for discomfort is only ulnar deviation.

How to tell ulnar deviation -  if looking down on hand if the skin is folding on the outside edge where the hand meets the wrist, there is ulnar deviation.

Split keyboard designs do not necessarily address other wrist deviations. Wrist Extension - Intra Carpal Pressure (ICP - measured in mm of mercury),  starts to rise quickly as hands move into wrist extension above 15 degrees..
In the seventies - there was no idea that wrist extension would be a problem and on older conventional keyboard you could rest your hands on the keys without activating them. This is less true of modern light touch keyboards, and wrist extension is a major problem.

How to tell wrist extension -  if looking down on hand if the skin is folding on the top of the hand at the wrist, there is undesirable wrist extension.

Keyboard layouts:
QWERTY keyboard layout: 

• 52% of usage is on top row
• 32% of usage is on middle row
• 16% of usage is on bottom row
• Left hand does most work (66% of keys)
• Hands may move up to 18 miles per day

DVORAK keyboard layout (1936):

• 70% of usage is on middle row
• 60% increase in speed
• Both hands doe comparable work
• Hands may move up to 2 miles per day

Maltron Layout (UK, 1970's) - uses cupped/dished key design:

• layout of keys to make least amount of movement
• used since mid-1970's in UK
• "Kinesis" keyboard in US uses similar layout
• Research shows that design improves hand posture but that typing speed may be reduced (at least initially)

Virginia PolyTechnic Institute (VPI),  Prof. Ed Kroemer - mid-60's tested split keyboard designs and published results in Human Factors journal.

Early 1990's - Apple split keyboard - also separate numeric key pad to go on either side (too big and bulky) - now defunct.

Some other split designs:

• Marquardt - Mini-Ergo
• Comfort Keyboard System - almost infinite hand positions, could be difficult to adjus
• Fold up keyboards - hands working vertically
• Data Hand - each key had switches, flick forward, backward, etc. but  hands are in extension when working
• Floating arms keyboard - attaches to side of chair
• Goldtouch keyboard - adjustable angle and tenting
• Chordic Keyboards - People can learn to type using key combinations (chords, like a Stenographer)
  - Eliminates normal keypads. "Bat" keyboard is one example. People generally daunted by learning curve.

Risk of musculoskeletal injury depends on : 

• Posture - deviated hand posture is a major risk factor for injury
• Force - small keyforces are multiplied by high repetition rates
• Stress - causes muscle tension which increase tendon loads
• Repetition - rate of repetition increases forces (e.g. OSHA estimates that a typist may press as much as 25 tons per day) 
  
• Rotation of hand may also be a risk factor:
  • - pronation - palm flat down, crossing of two bones (radius and ulna) may change the volume of carpal tunnel
  • - supination - palm up

Some vertical split keyboard designs place the hands mid pronate/supinate


Wrist Rests - low-cost, often useless, even dangerous devices.
Most wrist rests don't work effectively at all because people rest their wrists on them, which puts pressure on the carpal tunnel and restricts circulation to the hands..

• Modern keyboards often angle the keytops at 10 - 15 degrees which promotes wrist extension during typing
• People tend to hit keyboards too hard (3 - 8 times more forceful than necessary)
• People need tactile (and sometime auditory) feedback to show they've hit the right key.
• People who go buy wrist supports, etc., and don't get good results may say that Ergonomists' advice don't work, when the problem is an inappropriate product.

Wrist splint - these should not be used for any sustained time period if they put the hands into wrist extension - flat is better.

Arm supports (onto work surfaces) - not recommended because they can compress the flexor muscles.

Palm Support - recommended if they provide support to the thenar and hypothenar eminences (fleshy areas below thumb and little finger).

Negative slope keyboard trays - reduce keyboard angle by tilting a keyboard tray away from the user which puts the keys closer to 0 degrees to the hands. People have very similar typing styles even when keys presented a different angle, and typing performance isn't disrupted. A very effective solution.

Voice input
Some claim that keyboards may become obsolete and replaced by voice, but this is unlikely because:

• voice input is 1-channel and serial vs. keyboard input - 10-channels and almost parallel
• typing is faster than voice for sustained time periods
• repetitive strain problems with vocal chords - laryngitis, vocal chord nodules (25% of professional voice users develop these)?
• hard to draw by voice
• hard to correct errors by voice

Mouses
Many design force hand into wrist extension, and some force this into ulnar devation as well. Mouse  keys need ~ three times as much force as keyboard keys. Position of mouse determines postural risks - keep mouse close to body

Alternatives:

• Foot mouse - Foot operation more difficult to use, restricted range of motion
• Track balls - many designs force hand into wrist extension, and also where the device is located is critical.
• Trackpoint - small, finger operated joystick. Difficult to use for complex drawing. Puts high load on finger.
• Tocuhpad - quite good but small surface area can reduce pointing accuracy
• "Joystick" mouse - puts hand in better posture but location critical. 

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