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The author reviews the paper by Kroemer (1972) on the design of the split geometry keyboard and the subsequent 35 years of research on the topic. It was first suggested in the 1920s that arm strain in the typist could be reduced by splitting the keyboard into two halves and inclining the two halves laterally. The first systematic research on the split keyboard was conducted by Kroemer in the 1960s and published in his 1972 article. The literature on split geometry keyboards was identified, and the progression of the research was reviewed. The Kroemer article marked the beginning of a prolonged, worldwide research effort to determine whether and how the split keyboard design might improve comfort and prevent pain in keyboard users. In the early 1990s, split keyboard designs began to be broadly commercially available. Clear evidence of a health benefit of the split keyboards emerged in the late 1990s. By 2006, a split keyboard was the number one-selling keyboard, of all keyboards sold, in the U.S. retail market. The history of research on this topic, the challenges to changing the conventional design, and the broader acceptance of the split design are a success story with lessons for all of us.
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BACKGROUND
For the past 50 years, there has been increasing
recognition and evidence that long hours of key-
board use are associated with hand, arm, shoulder,
and neck pain and upper body musculoskeletal
disorders (Gerr, Monteilh, & Marcus, 2006).
These problems are related to work organizational
issues (e.g., hours of computer use per day, job de-
mands) as well as sustained awkward postures,
such as shoulder elevation, wrist ulnar deviation,
and head rotation. Some of these postural demands,
such as ulnar deviation, wrist extension, forearm
pronation, and shoulder abduction, are related to
the design of the conventional, straight keyboard.
There has been a long-standing interest in deter-
mining whether the split keyboard designs reduce
these postural demands and reduce upper body
pain in keyboard users.
The conventional, straight QWERTYkeyboard
design is based on the 1878 patent of Christopher
Latham Sholes (U.S. patent 207,559). The keys
are arranged in four staggered but straight rows,
as shown in Figure 1. In 1915, F. Heidner released
a patent with split keyboard designs (U.S. patent
1,138,474), which were to enable the operator to
write in a less cramped position, but the first re-
search on split keyboards did not occur until the
1920s.
In 1926, Klockenberg conducted a series of ex-
periments to assess subjective strain in the fore-
arms of typists. He suggested that the keyboard be
divided into two halves (one half for each hand)
and that the halves be laterally inclined to reduce
the muscle tension in the shoulders and arms.
These changes were expected to lead to less mus-
cular strain in the typists and to better typing per-
formance. He wrote that although these strains
may be small, they add up to considerable magni-
tude over many hours of keyboarding (Kroemer,
2001). There was relatively little work on the split
keyboard concept until the work of Kroemer in
the 1960s.
Definitions for positioning the two halves of a
split keyboard are presented in Figure 2. The
angles are based on a plane through the top of the
The Split Keyboard: An Ergonomics Success Story
David Rempel, University of California, Berkeley, Berkeley, California
Objective: The author reviews the paper by Kroemer (1972) on the design of the split
geometry keyboard and the subsequent 35 years of research on the topic. Back-
ground: It was first suggested in the 1920s that arm strain in the typist could be reduced
by splitting the keyboard into two halves and inclining the two halves laterally. The first
systematic research on the split keyboard was conducted by Kroemer in the 1960s and
published in his 1972 article. Methods: The literature on split geometry keyboards
was identified, and the progression of the research was reviewed. Results: The
Kroemer article marked the beginning of a prolonged, worldwide research effort to
determine whether and how the split keyboard design might improve comfort and pre-
vent pain in keyboard users. Conclusions: In the early 1990s, split keyboard designs
began to be broadly commercially available. Clear evidence of a health benefit of the
split keyboards emerged in the late 1990s. By 2006, a split keyboard was the number
one–selling keyboard, of all keyboards sold, in the U.S. retail market. Application:
The history of research on this topic, the challenges to changing the conventional
design, and the broader acceptance of the split design are a success story with lessons
for all of us.
Address correspondence to David Rempel, Ergonomics Program, University of California, Berkeley, 1301 South 46th Street,
Bldg. 163, Richmond, CA 94804; david.rempel@ucsf.edu. HUMAN FACTORS,Vol. 50, No. 3, June 2008, pp. 385–392. DOI
10.1518/001872008X312215. Copyright © 2008, Human Factors and Ergonomics Society.
GOLDEN ANNIVERSARY SPECIAL ISSUE
386 June 2008 –
Human Factors
alphabet keys for each half relative to the plane
of the work surface. Lateral inclination (β) is also
referred to as gable or tenting. The front-to-back
slope (α) is the angle of the plane about a line
through the top of the home row keys (i.e., A, S,
D, F, G or H, J, K, L). The opening angle (γ), also
referred to as split, rotation, or slant (slant is 1/2 the
opening angle), is the rotation of the plane about
the D or K key.
KROEMER’S (1972) “HUMAN
ENGINEERING THE KEYBOARD”
In a1972 publication in Human Factors, Dr. Karl
Kroemer summarized a series of experiments that
he carried out and published in the 1960s in Ger-
many. These studies evaluated the effects of a split
adjustable keyboard on user preference and pain.
In the first experiment, 38 participants simulated
the finger motion of typing while rotating the fore-
arms about their long axes. The most comfortable
forearm posture was approximately 40° to 55° of
pronation (in 0° pronation, the palms face each
other; at 90°, the palms face the desk surface); these
findings were similar to those in Klockenberg’s
study.
In the next experiment, participants typed on a
keyboard with different angles of lateral inclina-
tion. A split keyboard was built with an opening
angle of 30° with hinged halves adjustable from
and 90° of lateral inclination (Figure 3). Kroemer
called this the “K-keyboard” after Klockenberg.
Participants (N= 65) typed for 10 min at different
angles of lateral inclination and reported some
preference for 30° or 60° angles (Figure 4).
Figure 1. QWERTY keyboard layout from Christopher Sholes, 1878 U.S. patent (207,559).
Figure 2. Conventions for rotation of keyboard halves. α= slope, β= lateral inclination, γ= opening angle. The open-
ing angle is a rotation about the D and K keys (Tittiranonda, Rempel, Armstrong, & Burastero, 1999).
SPLIT GEOMETRY KEYBOARD 387
In the final experiment, 12 participants typed
for longer durations on a standard keyboard and
on the K-keyboard, which was set to an opening
angle of 50° and a lateral inclination of 45°. After
participants became familiar with the keyboards,
the typing error rate was less on the K-keyboard.
Pain was less on the K-keyboard in the back, arms,
and wrists but was greater in the shoulders. The
authors attributed the shoulder pain to too great an
opening angle leading to too much shoulder ab-
duction. The article concluded that the keyboard
halves should be laterally inclined to reduce pos-
tural muscular strain of the operator.
Although there were other advocates for the
split keyboard in the 1970s (Ferguson & Duncan,
1974), there was little published research on this
issue until the 1980s. This period from 1970 to the
early 1980s was also notable for the beginning of
reports from around the world on musculoskeletal
problems among data entry operators. These came
from Japan (Komoike & Horiguchi, 1971), Swit-
zerland (Laubli, Nakaseko, & Hunting, 1980), the
United States (Smith, Cohen, & Stammerjohn,
1981), Australia (McPhee, 1982), and other coun-
tries.
1980s: STANDARDS COALESCE
AROUND THE STRAIGHT
KEYBOARD DESIGN
Many journal articles and books were pub-
lished in the 1980s presenting research and opin-
ions on computer use, health, and productivity. The
IBM PC was introduced in 1981, and this marked
the rapid growth of computers in the office and
home. In the 1980s, the first comprehensive VDT
workstation design and use guidelines were pro-
mulgated, some with considerable attention to the
features of the conventional, straight keyboard
(Alden, Daniels, & Kanarick, 1972; ANSI/HFS-
100, 1988; Cakir, Hart, & Stewart, 1980; Interna-
tional Standards Organization [ISO], 1971). In
human factors circles, there was debate about the
Figure 3. The K-keyboard used in the Kroemer studies. The sides were hinged and inclined laterally from 0° to 90°
(Kroemer, 1972).
Figure 4. Experimental setup for the Kroemer studies.
Note that the participant cannot see the keyboard during
the typing task (Kroemer, 1972).
388 June 2008 –
Human Factors
design of the keyboard and concern that the con-
ventional QWERTY layout was becoming the
de facto standard (Alden et al., 1972), even though
the design was not optimal from a physiologic
standpoint (Arndt, 1984; Ferguson & Duncan,
1974; Ilg, 1987; Zipp, Haider, Halpern, & Rohm-
ert, 1983).
In Switzerland, Grandjean, Nakaseko, Hunting,
and Laubli (1981) published a series of experi-
ments on the split keyboard design that were later
summarized by Nakaseko, Grandjean, Hunting,
and Gierer (1985). They evaluated split keyboard
designs with more modest lateral inclination and
opening angles than those tested by Kroemer. The
upward slope was fixed at 10°. In one experiment,
the four keyboard designs tested were 0°, 0°; 15°,
0°; 25°, 10°; and 35°, 10° of opening angle and
lateral inclination, respectively. The split key-
boards included a built-in large (30 cm deep) fore-
arm support that was sloped to 8°. After 45 min of
use, the 20 typists most preferred the keyboard with
a 25° opening angle and 10° of lateral inclination.
Interestingly, the large sloped forearm support and
split keyboard, which was set higher (82 cm) than
the traditional keyboard (79 cm), induced the par-
ticipants to lean backward more in the chair, which
was one of the intentions of the researchers.
In a follow-up experiment, 31participants typed
for 30 min on a conventional keyboard and a split
keyboard with the large forearm support (opening
25°, lateral inclination 10°). Participants again
preferred the split keyboard. There was no differ-
ence in pain levels between keyboards, but par-
ticipants reported less arm, hand, and back tension
with the split keyboard. Ulnar deviation was re-
duced from 20° to 10°. The authors concluded that
the split keyboard design with a large forearm sup-
port will decrease ulnar deviation, decrease com-
plications in the forearm and hand, decrease the
static effect of hand pronation, and allow for a
more natural posture of the hands.
1990S: HEALTH EFFECTS OF
THE SPLIT KEYBOARD
The 1990s saw many more cross-sectional epi-
demiologic studies investigating musculoskeletal
problems among computer users (Bergqvist, Wol-
gast, Nilsson, & Voss, 1995; Bernard, Sauter, Fine,
Petersen, & Hales, 1994; Faucett & Rempel, 1994;
Sauter, Schleifer, & Knutson, 1991). A common
finding was a relationship between increasing
hours of computer use and prevalence of muscu-
loskeletal problems. Work organizational prob-
lems and awkward postures (e.g., head rotation,
shoulder flexion, and wrist extension) were also
related to upper body pain.
Mechanisms of injury were also being ex-
plored. In a commentary, Rose (1991) recom-
mended the split keyboard design to accommodate
the limit of forearm pronation of 60° to 70°. There
was some interest in the findings that the fluid
pressure in the carpal tunnel was elevated with the
forearm in full pronation or the wrist in extension
or in ulnar deviation. The pressure was lowest with
the forearm pronated to 45° compared with 0° or
90° (Rempel, Bach, Gordon, & Tal, 1998; Weiss,
Gordon, Bloom, So, & Rempel, 1995). The impli-
cations were that a neutral wrist posture and a non-
pronated forearm during typing would reduce the
risk of median nerve or tendon injury at the wrist.
Many split keyboards were developed and
brought to market by entrepreneurs in the 1990s
(Table 1), but only a few of them are still being
manufactured. Apple Computer launched the Ap-
ple Adjustable keyboard in 1992, and Microsoft
launched the Microsoft Natural keyboard in 1994.
The Apple keyboard had an adjustable opening
angle but no lateral inclination. The Microsoft
keyboard was a fixed split design with an opening
angle of 24° and a lateral inclination of 8°.
The 1990s also saw an explosion of laboratory
studies evaluating the effects of split keyboard
designs on productivity, preference, posture, and
pain. These were studies of adjustable keyboards,
fixed split keyboards, commercial keyboards, and
keyboards built just for research.
Across all studies, the productivity on split key-
boards was the same as or less than on a conven-
tional keyboard. Generally, productivity approached
that of a conventional keyboard after an hour to a
day of use (Cakir, 1995; Chen et al., 1994; Marklin
& Simoneau, 2001; Swanson, Galinsky, Cole,
Pan, & Sauter, 1997). Productivity was less for
split keyboards with more lateral inclination or
opening angle (Cakir, 1995; Chen et al., 1994;
Gerard, 1994; Muss & Hedge, 1999).
In most short-term studies, experienced typists
rejected the new split keyboard designs in favor
of conventional designs (Cakir, 1995; Honan,
Jacobson, Tal, & Rempel, 1996; Tittiranonda,
Burastero, Armstrong, & Rempel, 1999). How-
ever, when participants used split keyboards for
longer durations, 1 to 4 days, their preferences
switched toward neutral (Morelli, Johnson,
SPLIT GEOMETRY KEYBOARD 389
Reddell, & Lau, 1995; Zecevic, Miller, & Harburn,
2000). Several short-term studies used adjustable
keyboards to try to identify the most comfortable
geometry for typing (Thompson, Thomas, Cone,
Daponte, & Markison, 1990; Chen et al., 1994;
Tittiranonda, Burastero, et al., 1999). Needless to
say, there were large differences in design pref-
erences.
At least eight studies evaluated the effects of
the split keyboard design on wrist and forearm
postures (Chen et al., 1994; Honan, Serina, Tal,
& Rempel, 1995; Honan et al., 1996; Marklin, Si-
moneau, & Monroe, 1999; Muss & Hedge, 1999;
Smith et al., 1998; Tittiranonda, Burastero, et al.,
1999; Zecevic et al., 2000). Generally, the findings
of these studies were similar. When participants
typed on the split keyboards, the wrist and fore-
arms were in more neutral postures (i.e., less ex-
tension, less ulnar deviation, and less pronation
than when typing on a conventional keyboard).
Several studies also evaluated forearm mus-
cle activity while participants typed on split key-
boards. These studies reported a reduced activity
of some forearm or shoulder muscles when typing
on the split keyboard in comparison with a conven-
tional keyboard (Gerard, 1994; Marek, Noworol,
Wos, Karwowski, & Hamiga, 1992; Thompson
et al., 1990).
Although there was good evidence that the
split keyboards could reduce some of the posture-
related risk factors for musculoskeletal problems
and could reduce forearm muscle loads, the ques-
tion remained: Would the split keyboard designs
reduce pain? Several studies evaluated fatigue
and pain over 2 to 5 days of typing on split and
conventional keyboards (Morelli et al., 1995; Smith
et al., 1998; Swanson et al.,1997). None of the stud-
ies found a difference in upper body pain severity
between the keyboards studied.
However, a 6-month study found something
different. The end of the decade saw the first ran-
domized controlled trial evaluating the effects of
four keyboard designs on pain in patients with
hand or arm disorders (Tittiranonda, Rempel,
Armstrong, & Burastero, 1999). The study demon-
strated a reduction in pain in those who were as-
signed a fixed split keyboard compared with those
who received the conventional design. Interest-
ingly, the pain declined gradually among those
assigned the fixed split keyboard and was only
significantly different from that of the conven-
tional keyboard group after 412months (Figure 5).
At the end of the study, participants assigned to
the two adjustable keyboards reported less pain
than those using the conventional keyboard, but
the differences were not significant. Participants
were instructed on how to adjust these keyboards,
but they may have made relatively small geome-
try changes to the keyboards compared with the
conventional design.
2000s: THE ACCEPTANCE OF
THE SPLIT KEYBOARD
Two large, prospective studies provided solid
documentation of risk factors (e.g., hours of com-
puter use and awkward postures) associated with
upper extremity disorders and pain among com-
puter users (Gerr et al., 2002; Lassen et al., 2004).
In addition, more randomized controlled trials
were conducted that evaluated the health effects of
ergonomic and training interventions among com-
puter users. These studies are summarized by large
systematic reviews (Brewer et al., 2006; Verhagen,
Karels, & Bierma-Zeinstra, 2006).
TABLE 1: Partial List of Split Geometry Keyboards
Fixed Split Adjustable
ErgoMax/SafeTypeaApple Adjustable
Logitech Ergo Split Cherry Ergo-Plus
Logitech WaveaComfort
Kinesis ContouredaDatahand
Marquardt KeyOvation Goldtoucha
Maltron Keytronic FlexPro/ErgoLogic
Microsoft Natural Kinesis Maxima
Microsoft Natural EliteaLexmark M15/SelectEase
Microsoft Natural Ergonomic 4000aTONY!
Microsoft Comfort Curvea
STR
aStill being manufactured.
390 June 2008 –
Human Factors
Through the 2000s, there were more laboratory
studies investigating the effects of split geometry
keyboard designs on postures and tissue loads
(Simoneau, Marklin, & Berman, 2003; Marklin &
Simoneau, 2004; Rempel, Barr, Brafman, &Young,
2007; Rempel, Keir, & Bach, in press; Rempel,
Nathan-Roberts, Chen, & Odell, in press). These
studies tended to evaluate more subtle differences
in keyboard design changes on posture than dur-
ing the previous decade. It should be noted that
these studies used participants who were touch
typists; the split keyboard may provide little ben-
efit to nontouch typists.
The National Institute for Occupational Safety
and Health (NIOSH) conducted a 2-year ran-
domized controlled trial to evaluate the effects of
different keyboard designs on pain and upper
extremity disorders among 289 computer users
(Moore & Swanson, 2003). Participants were ran-
domized to receive a conventional keyboard, a
fixed split keyboard, or an adjustable split key-
board. The study found that the fixed split keyboard
prevented the occurrence of new symptoms in the
neck region. Both split keyboards also reduced
pain in the hands, wrists, and forearms among
those computer users with pain at the beginning
of the study. The study provides the strongest evi-
dence to date for both a primary and secondary
prevention benefit of the split keyboard on upper
body musculoskeletal health.
The design of commercial split keyboards
evolved during the 2000s. The latest Microsoft
split keyboard has a steeper lateral inclination (14°
instead of 8°) to further minimize forearm prona-
tion and curved key rows to reduce finger reach
during typing. In 2006, a fixed split keyboard
(Microsoft Natural Ergonomic Keyboard 4000)
became the best-selling aftermarket, wired key-
board, of all wired keyboards, not just ergonomic
keyboards, sold in the United States (NPD Group,
2006).
DISCUSSION
It was first proposed in 1926 that a split geom-
etry keyboard would reduce muscle strain during
Figure 5. Changes in mean overall pain severity by the keyboard group from the Tittiranonda, Rempel, Armstrong,
and Burastero (1999) study. The placebo is a conventional design, KB1 is the Apple Adjustable keyboard, KB2 is the
Comfort keyboard, and KB3 is the Microsoft Natural keyboard. The decline in pain in KB3 is significantly different
from the placebo (open diamonds) and from the beginning pain scores (*) at Weeks 18 and 24 (N= 80).
SPLIT GEOMETRY KEYBOARD 391
typing compared with a conventional keyboard
design by reducing forearm pronation. With his
1972 paper, Kroemer rekindled an interest in the
split keyboard with the first studies that demon-
strated an effect of keyboard design on productiv-
ity, preference, and pain. This coincided with the
beginning of reports from around the world of
musculoskeletal problems among data entry oper-
ators. In the 1980s, Swiss and German research
groups provided more physiologic evidence in
support of the split keyboard design. Although the
conventional keyboard design was perceived by
some in the human factors community as being in-
efficient and associated with increased arm strain,
there was little interest from industry in modifying
the design. In fact, ISO, DIN, and ANSI standards
coalesced around the conventional keyboard
design.
The rapid growth of personal computers in
1980 was accompanied by more reports of mus-
culoskeletal problems among computer users and
more laboratory studies of the effects of the split
keyboard on muscle load, posture, productivity,
and preference. There were scattered efforts by
entrepreneurs to market split keyboards, but these
efforts were usually short-lived. Apple computer
was the first large computer manufacturer to de-
velop a split keyboard in the early 1990s, and it was
soon followed by Microsoft. The first randomized
controlled trial of split keyboards in 1999 demon-
strated a positive health effect, and these findings
were later confirmed by a much larger study.
Overall, the research literature demonstrates a
number of important lessons. First, subjective
preference may not be sensitive to ergonomic
benefits for devices that are used repetitively but
require low activation forces. Second, health ben-
efits of ergonomic keyboards were not apparent in
short-term (2- to 5-day) studies of discomfort and
pain but were observed only after 4 months of use.
Third, in short-term studies, ergonomic principles
(i.e., the reduction of postural risk factors and
muscle loads) predicted positive health outcomes.
Finally, the ideal keyboard design has yet to be
identified; there is still much to be done on the
geometry of the keyboard and keys. It may even
be possible to incorporate features of the split
keyboard design into laptop computers.
The history of the adoption of the split key-
board design is an unusual one in human factors
research. Split keyboards are not associated with
increased productivity – the main value is im-
proved health. Kroemer’s (1972) research opened
the door to considering ergonomics in the design
of keyboard geometry. This was followed by re-
search in other laboratories that confirmed and
refined his initial findings. However, the wide-
spread adoption of the split keyboard did not occur
until two factors converged. One, a couple of large
but relatively young computer software manu-
facturers committed to developing keyboards with
the goal of improving worker and customer health.
Two, laboratory and field research demonstrated
a health value related to the split keyboard de-
signs. We should be alert for other such opportu-
nities to promote health and injury prevention in
the workplace.
ACKNOWLEDGMENTS
No funds were received for the preparation of
the manuscript, but research in Professor Rempel’s
laboratory has been supported by gifts from Mi-
crosoft, Apple, Logitech, and the Keytronic Cor-
poration.
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David Rempel is the director of the Ergonomics Program
at the University of California at Berkeley and professor
in the Department of Bioengineering at UC Berkeley
and the Department of Medicine at UC San Francisco.
He received his M.D. degree in 1982 from UC San
Francisco.
Date received: December 8, 2007
Date accepted: April 25, 2008
... For the keyboard, tilt and rotation angles and key switch design and force profile have all been suggested as parameters that can be adjusted to address biomechanical loading and musculoskeletal outcome concerns (e.g. [19][20][21]). ...
... A more general review of the biomechanical loading effects of alternative keyboards with varying slope angles, opening angles, lateral inclination angles, and separation distances was performed by Rempel [21]. This review also incorporated information on musculoskeletal outcomes. ...
... As also observed in Rempel's review, the effect of alternative input devices on productivity, performance, discomfort, and user preference was dependent on the time spent using the devices [21]. Many short term experimental studies reported decreased productivity, performance, and preference and increased discomfort when using alternative pointing devices or keyboards (e.g. ...
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... Clearly, the results obtained with split soft keyboards reported herein and in the related studies [20,21] are negative and disagree with many of the studies of physical split keyboards [12][13][14][15][16]. One possible explanation for this is that the controlled studies with physical keyboards were conducted using ten finger touch typing while the controlled studies with soft keyboard where performed using hunt-and-peck for keys. ...
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Soft Qwerty keyboards are widely used on mobile devices such as tablets and smartphones. Research into physical keyboards have found split keyboards to be ergonomically better than ordinary physical keyboards. Consequently, the idea of split keyboards has also been applied to tablet soft keyboards. A controlled experiment with n = 20 participants was conducted to assess if split soft keyboards pose an improvement over ordinary soft keyboard on tables with both one-handed and two-handed use. The results show that the split keyboard performs worse than ordinary keyboards in terms of text entry speed, error rate and preference.
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... A variation on QWERTY is the split keyboard ( Figure 2) which evolved from Kroemer's work in the 1960s (Rempel, 2008). A variation on the split keyboard is the half-QWERTY keyboard which was designed to facilitate the transfer of two-handed typing skill to one hand (Matias et al., 1993). ...
... Alternative keyboards were introduced in the 1990s with designs based on the findings of several investigators (Kroemer 1972, Buesen 1984, Nakaseko et al. 1985, Ilg 1987). A review article by Rempel (2008) provides a summary of the published research on split keyboards between 1926 and 2007. Fixed-split keyboards (Figure 1) reduce awkward postures (Honan et al. 1995, Rempel et al. 1995, Honan et al. 1996, Marklin et al. 1999, Zecevic et al. 2000), muscle strain (Strasser et al. 2004) and overall pain and discomfort as well as improving the functional status of participants with pre-existing hand and wrist pain (Tittiranonda 1997, Tittiranonda et al. 1999). ...
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Alternatively configured keyboards have been extensively marketed as one method to reduce musculoskeletal symptoms and musculoskeletal disorders in computer operators. This paper reviews current evidence about the effectiveness of alternative keyboards at reducing risky postures and improving musculoskeletal symptoms. In general, the literature strongly supports the ability of alternative keyboards to reduce potentially risky postures, but is much more equivocal about their ability to reduce musculoskeletal symptoms in the workplace.
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This study utilizes a variable geometry keyboard to analyze the optimal configuration for a split QWERTY-type keyboard. The measured criteria were muscle activity as measured by EMG and reported operator discomfort. A variable geometry keyboard, simultaneously adjustable in opening angle (yaw) and lateral angle (roll) was obtained. The upward slope (tilt) was preset at 10%. The study manipulated the keyboard geometry to assess the difference in musculoskeletal activity between using (1) a conventional, flat, linear keyboard; (2) a neutral, undeviated wrist position; and (3) two forearm positions that essentially eliminate pronation. Eight experienced subjects with no prior history of wrist injury or other pathology were tested. EMG activity of four relevant muscle groups was measured on each subject for each of the four keyboard positions. The study suggested an 18° opening angle and a 30°–60° lateral angle as optimal when compared with a flat, standard keyboard (they minimize objective EMG activity and subjective discomfort).
Twenty experienced typists participated in a laboratory based study to determine whether wrist and forearm postures changed over a 4 hour period of intensive keyboard use. Subjects were randomly assigned to use a conventional keyboard or a fixed split keyboard. Posture data was acquired using electrogoniometers after a 10 warm-up period and at the end of each hour. Wrist and forearm postures did not change significantly over the four hour period among subjects using the split geometry keyboard. On the conventional keyboard, all joint postures were stable except right wrist extension and left forearm pronation. The right wrist extension increased by 5° over the four hour period (p=.002) and left pronation decreased by approximately 9° (p=.001). Wrist postures among typists exposed for the first time to a split keyboard remained constant throughout a four hour period of intensive typing. On the conventional keyboard, some postures drifted over the four hour period.
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A search of the psychological, technical, and promotional literature was conducted to compile information relevant to key, keyboard, and operator characteristics. The most recent and significant articles were discussed and evaluated. Where possible, general conclusions have been drawn to aid the keyboard designer.
Fifty experienced typists participated in a laboratory based repeated measures study with two factors: keyboard height (three) and keyboard configuration (three). The work surface heights tested were 63, 67 and 71 cm. The three keyboard configurations tested were: standard (Apple Extended™), alternative keyboard A (Microsoft Natural Keyboard) and alternative keyboard B (equivalent to Natural Keyboard with Leveler™ extended). Wrist and forearm posture data was acquired using electronic goniometers during 10 minutes of typing at each keyboard/height level. Across all heights tested, wrist extension, wrist ulnar deviation, and forearm pronation were statistically significantly closer to neutral when using alternative keyboard B than when using the standard keyboard.
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The design of keyboards is still characterized by that of mechanical typewriters. This paper presents a summary of a research project dealing with the ergonomic improvement of keyboards, carried out at the IAO in Stuttgart during the past five years. Extensive laboratory evaluation of experimental keyboards, where different design parameters were tested under real life conditions, have produced a relative optimum regarding ergonomic keyboard design. An accompanying investigation of user acceptance evaluated all realized parameters. In co-operation with a keyboard manufacturer, the results were used to design a marketable product, which may be seen as an important contribution to ergonomic keyboard design.
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Video display terminal (VDT) operators (n = 150) in the editorial department of a large metropolitan newspaper participated in a study of day-to-day musculoskeletal symptoms. Work posture related to the VDT workstation and psychosocial work factors were also investigated for their contributions to the severity of upper body pain, numbness, and stiffness using a representative subsample (n = 70). Self-report measures included Karasek's Job Content Instrument and the author-designed Work Interpersonal Relationships Inventory. Independent observations of work posture were performed using techniques similar to those reported by Sauter et al. [1991]. Pain during the last week was reported by 59% (n = 88) of the respondents, and 28% (n = 42) were categorized by symptom criteria potentially to have musculoskeletal disorders. More hours per day of VDT use and less decision latitude on the job were significant risk factors for potential musculoskeletal CTDs. Head rotation and relative keyboard height were significantly related to more severe pain and stiffness in the shoulders, neck, and upper back. Lower levels of co-worker support were associated with more severe hand and arm numbness. For both the region of the shoulders, neck, and upper back and the hand and arm region, however, the contributions of relative keyboard and seat back heights to symptom severity were modified by psychological workload, decision latitude, and employee relationship with the supervisor. Alternative explanations for these findings are discussed.
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Eighty computer users with musculoskeletal disorders participated in a 6-month, randomized, placebo-controlled trial evaluating the effects of four computer keyboards on clinical findings, pain severity, functional hand status, and comfort. The alternative geometry keyboards tested were: the Apple Adjustable Keyboard™ [kb1], Comfort Keyboard System™ [kb2], Microsoft Natural Keyboard™ [kb3], and placebo. Compared to placebo, kb3 and to a lesser extent kb1 groups demonstrated an improving trend in pain severity and hand function following 6 months of keyboard use. However, there was no corresponding consistent improvement in clinical findings in the alternative geometry keyboard groups compared to the placebo group. Overall, there was a significant correlation between improvement of pain severity and greater satisfaction with the keyboards. These results provide evidence that keyboard users may experience a reduction in hand pain after several months of use of some alternative geometry keyboards. Am. J. Ind. Med. 35:647–661, 1999. Published 1999 Wiley-Liss, Inc.
Article
BackgroundA prospective study of computer users was performed to determine the occurrence of and evaluate risk factors for neck or shoulder (N/S) and hand or arm (H/A) musculoskeletal symptoms (MSS) and disorders (MSD).Methods Individuals (n = 632) newly hired into jobs requiring  ≥ 15 hr/week of computer use were followed for up to 3 years. At study entry, workstation dimensions and worker postures were measured and medical and psychosocial risk factors were assessed. Daily diaries were used to document work practices and incident MSS. Those reporting MSS were examined for specific MSD. Incidence rates of MSS and MSD were estimated with survival analysis. Cox regression models were used to evaluate associations between participant characteristics at entry and MSS and MSD.ResultsThe annual incidence of N/S MSS was 58 cases/100 person-years and of N/S MSD was 35 cases/100 person-years. The most common N/S MSD was somatic pain syndrome. The annual incidence of H/A MSS was 39 cases/100 person-years and of H/A MSD was 21 cases/100 person-years. The most common H/A disorder was deQuervain's tendonitis. Forty-six percent of N/S and 32% of H/A MSS occurred during the first month of follow-up. Gender, age, ethnicity, and prior history of N/S pain were associated with N/S MSS and MSD. Gender, prior history of H/A pain, prior computer use, and children at home were associated with either H/A MSS or MSD.ConclusionsH/A and N/S MSS and MSD were common among computer users. More than 50% of computer users reported MSS during the first year after starting a new job. Am. J. Ind. Med. 41:221–235, 2002. © 2002 Wiley-Liss, Inc.