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Keyboards Designed to Fit Hands and Reduce Postural Stress. Paper presented by S.W. HOBDAY at the NINTH CONGRESS OF THE INTERNATIONAL ERGONOMICS ASSOCIATIONS, 2-6 September 1985, Bournemouth, England.

KEYBOARDS DESIGNED TO FIT HANDS & REDUCE POSTURAL STRESS

S.W. HOBDAY

PCD Maltron Ltd.



DESIGN PHILOSOPHY

The flat, rectangular, typewriter style keyboard has been around for so long that a severe shock occurs when an entirely new shape is presented as an office machine keyboard. Electronics have increased keyboard use and provided conditions for revision by separating keys from printer. In 1976 Lillian malt and I, alerted to operator distress by a Duncan Ferguson paper of 1974, developed the idea of curving the keyboard to fit natural finger movements and take into account the very obvious fact that fingers are not all the same length. Duncan & Ferguson showed correlation between hand abduction and operator complaints, making it essential for any new design to reduce abduction to zero if a major source of stress was to be removed. Flat keyboard operation needs hand pronation almost to the limit. This requires sustained muscle tension. These two postural stresses are relieved by slightly raising the shoulders, but this in turn gives rise to fatigue and pain in these muscles.

To meet these factors the new keyboard is shaped in three dimensions, and allows hand movements to occur naturally with minimum stress. Separation of the letter keys into two spaced groups has reduced abduction to zero. By designing for radial finger movement over keys at differing heights to suit lengths and by sloping the rows downwards from the centre, pronation stress has been reduced. The design was first described by Lillian Malt in 1977, and the author in 1981. A report by P. Zipp et al in 1983, confirmed the design philosophy concerning reduction of muscle tension.

As detailed in Lillian Malt's paper, a new letter layout has 90% of the letters of the 100 most used words on the home row, including E (11% of keystrokes) on the normally unused left thumb, instead of 52% for Qwerty. This leads to a reduction of 11:1 in successive finger use and a 250:1 drop in "hurdles" (the need to move a finger from home row up or down and then across to the key below or above). The result is a substantial reduction in work load.

For already trained operators in situations where interruption of output for retraining is not possible, the Maltron - Qwerty changeover key, and the provision of dually engraved keytops, allows them to enjoy the benefit of the new shape. Initial adaptation practise takes about an hour, followed by a day or so of work to regain full performance.

 

RESULTS

(a) A Qwerty operator with a skill level of 80 wpm, adapted herself and regained her original level in a few hours, and has since improved this to 100 wpm. She confirms much reduced fatigue and higher accuracy. She has experienced no problems in using both flat and shaped keyboards during the normal working day.

(b) The accurate tactile feedback provided by the shaped key groups and the ease of using the new letter layout has demonstrated an initial learning time reduction of 3-4:1 by commercial students, (W.M. Heath 1981) and even more by a business executive. (M. Moffatt 1983).

(c) Eight operators of 1 - 11 years experience, after 10 days training on W.P. equipment, produced 60-174% of their qwerty speeds and subsequently reported less tiring, comfortable, and more accurate operation with no confusion in using both new and old keyboards. (J. Sions 1980).

(d) Four typesetters, with up to 30 years keyboard experience, keying complicated mathematical and scientific articles at speeds of 61-98 words per minute, had an average error rate of 0.46%. After 18 days training, on the new keyboard speeds were 49-65 wpm. with an error rate of 0.32%. In subsequent production work this has fallen to 0.05% with a daily output of 80-95,000 keystrokes. The operators confirm that the new keyboard is much less tiring to use. The medically diagnosed "arthritis" in the fingers of one has completely cleared.

 

CONCLUSIONS

Operator experience confirms that the design targets of reduced stress and work load have been achieved. From this it can be expected that the wider use of an ergonomically shaped keyboard would reduce the incidence of repetitive strain injury now being reported by keyboard operators. (A. Horin, 1984. J. Kavanagh, 1984. CPSA, 1985.)

As a matter of some urgency, a new international standard for a fully ergonomic keyboard is required. The new letter layout developed for this keyboard is suitable for all Latin alphabet based languages. The easily accessible extra finger and thumb keys, which the design provides, can cover language variables while the main groups remain the same for all. This would meet the requirement for a keyboard common to Western Europe and North and South America.




REFERENCES

CPSA Research Department, January (2) 1985, The office workers industrial disease. Red Tape, Vol. 74, No. 8.

Duncan, J., &mp Ferguson, D., November 1974, Keyboard design and operating posture. Ergonomics, p.731.

Heath, W.M., Basingstoke Technical College, January 1981, Maltron Keyboard. Unpublished but available from S.W.Hobday.

Hobday, S.W., January 1981, The quick brown fox... or keyboard alternative. The Inventor, Vol. 81, No. 1, p.16.

Horin, A., l2th. October 1984, Hi-Tech epidemic. The National Times, Sydney, p.15.

Kavanagh, J., l7th. November 1984, Keyboard cripples. Business Review Weekly, Melbourne, p.37.

Malt, L.G., September 1977, Keyboard design in the electronic era. Printing Industry Research Association Symposium, Paper No.6. Moffatt, M., September 1983, Report on use of Maltron keyboards.

Unpublished but available from S.W.Hobday.

Sions, J., August 1980, Qwerty under fire. The International Word Processing Report, Vol. 6/5, p.3.

Zipp, P., Haider, E., Halpern, N., and Rohmert, SV., June 1983, Keyboard design through physiological strain measurements. Applied Ergonomics, Vol . 14.2, p.117.



Paper presented by: S.W. HOBDAY at the:

NINTH CONGRESS OF THE INTERNATIONAL ERGONOMICS ASSOCIATIONS

2-6 September 1985, Bournemouth, England.

Paper F1/2 (p 457 of proceedings)

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