Evidence-based guidelines for the wise use of computers by children: Physical development guidelines

Abstract

Computer use by children is common and there is concern over the potential impact of this exposure on child physical development. Recently principles for child-specific evidence-based guidelines for wise use of computers have been published and these included one concerning the facilitation of appropriate physical development. This paper reviews the evidence and presents detailed guidelines for this principle. The guidelines include encouraging a mix of sedentary and whole body movement tasks, encouraging reasonable postures during computing tasks through workstation, chair, desk, display and input device selection and adjustment and special issues regarding notebook computer use and carriage, computing skills and responding to discomfort. The evidence limitations highlight opportunities for future research. The guidelines themselves can inform parents and teachers, equipment designers and suppliers and form the basis of content for teaching children the wise use of computers. STATEMENT OF RELEVANCE: Many children use computers and computer-use habits formed in childhood may track into adulthood. Therefore child-computer interaction needs to be carefully managed. These guidelines inform those responsible for children to assist in the wise use of computers.

Full text

Evidence-based guidelines for the wise use of computers by children: Physical development
guidelines
L. Straker
a
*, B. Maslen
a
, R. Burgess-Limerick
b
, P. Johnson
c
and J. Dennerlein
d
a
School of Physiotherapy, Curtin University of Technology, GPO Box U1987, Perth, WA 6845, Australia;
b
Human Movement
Studies, University of Queensland, Brisbane, Australia;
c
Department of Environmental and Occupational Health Services,
University of Washington, Box 354695, Seattle, Washington 98195, USA;
d
Harvard School of Public Health, 665 Huntingdon
Avenue, Boston, MA 02115, USA
(Received 18 June 2009; final version received 30 November 2009)
Computer use by children is common and there is concern over the potential impact of this exposure on child
physical development. Recently principles for child-specific evidence-based guidelines for wise use of computers have
been published and these included one concerning the facilitation of appropriate physical development. This paper
reviews the evidence and presents detailed guidelines for this principle. The guidelines include encouraging a mix of
sedentary and whole body movement tasks, encouraging reasonable postures during computing tasks through
workstation, chair, desk, display and input device selection and adjustment and special issues regarding notebook
computer use and carriage, computing skills and responding to discomfort. The evidence limitations highlight
opportunities for future research. The guidelines themselves can inform parents and teachers, equipment designers
and suppliers and form the basis of content for teaching children the wise use of computers.
Statement of Relevance: Many children use computers and computer-use habits formed in childhood may track into
adulthood. Therefore child–computer interaction needs to be carefully managed. These guidelines inform those
responsible for children to assist in the wise use of computers.
Keywords: children; computers; guidelines; musculoskeletal disorders
1. Introduction
Computer use by children is common and likely to
have physical, cognitive and social impacts. Previous
papers have argued the need for child-specific evi-
dence-based guidelines (Straker and Pollock 2005,
Straker et al. 2006a,b) and presented general principles
for wise use of computers by children (Straker et al.
2009b). One of these principles concerned the physical
impact, specifically the risk of musculoskeletal dis-
orders (MSDs) and other physical health outcomes.
The aim of this paper was to review the evidence
relating to physical aspects of the child–computer
interaction. A narrative review approach was selected
because of the variable nature of available evidence.
Based on the evidence, a set of guidelines covering
physical aspects of the child–computer interaction are
presented (see summary in Table 1). Whilst these
guidelines can be used to guide computer use practices
directly, they are also intended to be the basis for
education of children, teachers and the parents of
children so that child computer users are aware of the
issues and develop appropriate computer-use habits to
take into adulthood.
2. The physical guidelines
2.1. Encourage a mix of sedentary tasks and whole
body movement tasks
The first few physical guidelines are all related
to encouraging a mix of whole body movement
tasks with the, generally, sedentary computing
tasks. This guideline is aimed at providing
sufficient whole body activity to facilitate
appropriate neuro-musculo-skeletal development and
to minimise the risk of musculo-skeletal and other
health disorders.
2.1.1. Encourage task variety
There is a general consensus that variation of movement
and load on the body is important for reducing the risk
of MSDs, although Mathiassen (2006) cautioned that
direct evidence for this assertion is weak. The aetiology
of MSDs is multifactorial and may include workstation
parameters, psychosocial stress, posture and force-
related exposures related to anthropometry (size and
strength), rest break schedules and individual differences
in motor control strategies. All of these contribute and
*Corresponding author. Email: l.straker@curtin.edu.au
Ergonomics
Vol. 53, No. 4, April 2010, 458–477
ISSN 0014-0139 print/ISSN 1366-5847 online
!2010 Taylor & Francis
DOI: 10.1080/00140130903556344
http://www.informaworld.com
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interact under relatively low biomechanical load
conditions (Jensen et al.1993,Johnsonet al.2000,
Wahlstrom et al.2000,DennerleinandJohnson2006,
Johnson and Blackstone 2007), which may be sustained
for many hours. Although the value of task variation is
intuitively appealing, it may therefore be difficult to
empirically isolate the effects of variation. Westgaard
(2000) noted that it is difficult to detect risk factors at
low biomechanical exposures.
Attempts to increase exposure variation through
task variation have included introducing pauses within
work tasks (e.g. taking breaks), deliberately working
using a mixture of keyboard and mouse use, switching
hands when using the pointing device (e.g. mouse),
switching between pointing devices with different
biomechanical demands (e.g. a mouse and a trackball)
and introducing different work tasks (e.g. intentionally
breaking up computer work with meetings).
2.1.1.1. Task variety through pauses. While there have
been some benefits of introduced pauses, and software
that introduces pauses into the work pattern is used by
Table 1. Guidelines for desktop/notebook use to encourage appropriate physical development.
1.1 Encourage a mix of sedentary and active tasks
1.1.1. Encourage task variety through breaks and changing tasks
Mix computer tasks with non-sedentary/active tasks**
Take an active break from the computer every 30–60 min **
1.1.2. Encourage use of active input devices
Use active input devices whenever possible**
1.1.3. Encourage postural variety
Encourage children to fidget and move around whilst using computers *
1.1.4. Limit sedentary use of computers
Limit the use of sedentary electronic equipment for leisure purposes to less than 2 h per day*
1.2 Encourage reasonable postures during sedentary tasks
1.2.1 Encourage a range of suitable postures through appropriate workstation design
Select/adjust workstation size to suit the child***
Design workstations to enable a range of suitable postures**
Use standing and sitting workstations*
1.2.2 Encourage a range of suitable seated postures by selecting and adjusting chair appropriately
Set seat pan height to allow feet to be supported***
It may be appropriate to not have a backrest
If a backrest is provided the seat pan should be shorter than thigh length and the backrest
should fit the child’s lumbar spine
Avoid armrests
Select seat style to support a range of reasonable postures
1.2.3. Encourage suitable postures by selecting and adjusting an appropriate work surface
Set desk height to around elbow height*
Select large enough desk surface to permit appropriate positioning and use of keyboard, mouse and other materials
Select a single flat thin surface
Use document holders and inclined supports to position paper materials close to the display
1.2.4. Encourage appropriate postures and gaze angle by selecting and positioning computer display appropriately
Set top of display at eye height**
Position display at about arm’s length and directly in front
Position display to avoid glare
Select a good quality display
1.2.5. Encourage appropriate postures by selecting and positioning keyboard and pointing device appropriately
Select symmetrical mouse of appropriate size *
Enable mouse use on either side of keyboard
Provide thin flat keyboard to reduce wrist extension
Provide a smaller keyboard for smaller children
Provide a keyboard without numeric keypad
Select mouse and keyboard with suitable activation forces
1.3 Encourage appropriate behaviour when using and transporting notebook computers
Provide notebook of low weight
Carry notebook in dual shoulder strap backpack*
Provide external keyboard and adjust display height for larger children*
Encourage use of appropriate alternative postures for variety
1.4 Teach children computing skills
Learn to touch-type with minimum force*
Learn keyboard shortcuts to reduce mouse use
Learn to use software
1.5 Teach children to respond to discomfort*
Ergonomics 459
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more than one million computer users (Slijper et al.
2007), evidence for the benefit of short pauses is mixed.
AreviewofworkplaceinterventionsbyBreweret al.
(2006) found mixed evidence for the effect of rest
breaks on musculoskeletal outcomes and insufficient
evidence to conclude that rest breaks affected visual
outcomes. However, limited rest break opportunities
have been linked to musculoskeletal problems in adult
computer users (Bergqvist et al. 1995). The timing and
length of pauses may be influential; Blangsted et al.
(2004) found no difference in electromyographic levels
with 30 s vs. 4 min breaks in a one-handed keying task.
Muscle activity during the breaks did not differ
between keying and non-keying sides and during
the pauses it was above resting level. Hagberg
and Sundelin (1986) found a significant negative
correlation between spontaneous pauses and static
trapezius load, but not between introduced pauses and
static load. The introduced pauses were, however,
associated with a lower rating of perceived exertion. In
a study of the efficacy of pause software, spontaneous
pauses were reported to correspond closely to the
timing of introduced micropauses. However, the
software enforced longer pauses (greater than 5 min)
before the operator would naturally take a break
(Slijper et al. 2007).
Performance decrements have been noted in adult
computer operators after approximately 45–50 min of
computer work (Floru et al. 1985, Gao et al.1990)and
it has been recommended that breaks be taken after
40–60 min (Floru et al.1985,Gaoet al.1990,
Kopardekar and Mital 1994, Boucsein and Thum
1995). During simulated directory assistance work,
comparison of a 60 min on/10 min offwork/rest
schedule with a 30 min on/10 min offschedule revealed
no difference in performance (Kopardekar and Mital
1994). In contrast, Balci and Aghazadeh (2004) found
the introduction of a micropause regimen (breaks of
30 s to 3 min every 15 min) to be superior to two
longer rest break schedules in terms of musculoskeletal
discomfort, eyestrain and performance. In another
study, four supplementary 5 min work breaks inserted
into the usual workday pattern of 51 data entry
operators were found to reduce musculoskeletal
discomfort and eyestrain, with no decline in produc-
tivity (Galinsky et al.2007).Thereisnoconsensus
regarding the optimal schedule for work/rest breaks
and it is likely to be dependent upon many factors,
including the task, input device and individual – for
example, highly repetitive keying tasks such as data
entry may benefit from different pause regimens when
compared to mouse-intensive tasks such as computer-
aided design.
The introduction of pauses into computing tasks by
children appears not to have been examined directly.
Computer use at home has been reported to be
characterised by longer maximum durations than at
school (Harris and Straker 2000), suggesting that
breaks during home use may be more important.
It is noteworthy that studies of introduced rest
breaks for adults do not tend to find negative effects on
either discomfort or productivity and some studies
have reported beneficial effects. It is likely that the
introduction of pauses and rest breaks can be of
benefit, but a particular schedule of rest breaks is
difficult to justify. The task of identifying the most
effective rest break schedules for the many different
work patterns, which are likely to occur for both adults
and children, is a daunting one.
2.1.1.2. Task variety through changing tasks.
Different computer tasks such as keyboard entry,
numerical data entry, mouse-intensive tasks and
reading from a display or document apply differing
stresses to the body. Mouse tasks tend to be more
constrained and have lower variation in forearm
muscle activity than keyboard tasks (Dennerlein and
Johnson 2006b). A study of Irish children aged 9 years
found that pain after a computing session was related
to the task performed, with increased neck pain for
those children who primarily used the mouse (Breen
et al. 2007). Mouse use has also been associated with
musculoskeletal symptoms in adult users (Ijmker et al.
2007). Keyboard tasks are associated with greater
variation but have less neutral wrist postures and
larger wrist velocities. Different input devices such as
trackpoints also affect which structures are loaded
(Fernstro
¨mandEricson1997).Therefore,amixtureof
keyboard and mouse use may provide some exposure
variation (Dennerlein and Johnson 2006b).
Computer tasks tend to offer less variation in
posture and muscle activity than paper-based tasks,
both for adults (Wærsted and Westgaard 1997, Straker
et al.2009b)andchildren(Strakeret al. 2008c, 2009d).
Postures during computer work, however, tend to be
more neutral and symmetrical than those using old IT
(paper-based information technology) (Straker et al.
2008b, 2009d). A mixture of old and new (electronic
based) IT tasks may therefore provide some variation
and be of benefit.
Perhaps the most effective method to encourage
physical variety is to mix computer tasks with non-IT
tasks. For example, alternating computer data entry
with delivering mail. Non-IT tasks have been found to
provide more postural and muscle activity variation in
both adults and children (Ciccarelli et al. 2006, 2009,
Maslen and Straker 2009).
Children do not always use computers in a similar
manner to adults – they may share school computers
between two or more users (Sotoyama et al.2002,
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Breen et al.2007)andathometheyfrequentlyuse
other forms of technology such as phones and MP3
players simultaneously with the computer (Kent and
Facer 2004, Roberts et al.2005,Foehr2006).Such
usage patterns may inherently offer more postural and
load variation for the body and should, therefore, not
necessarily be discouraged, providing they do not
interfere markedly with performance, for example, of
homework tasks. However, children may also get
highly involved in a computer task and may continue
even when experiencing discomfort (Harris and
Straker 2000), so it is important to encourage rest
breaks or task changes.
Based on the available evidence, it is recommended
that children should be encouraged to take a break
from computer work every 30 min and not be allowed
to work more than 60 min without a break from the
computer These breaks should be physically active and
meaningful to the child, rather than a sedentary break
(e.g. sitting watching TV, playing video games or using
amobilephone).
It is anticipated that it will be fairly easy for
teachers to implement this guideline at school, as
children frequently need to change rooms or move
around within a classroom to perform their school
tasks. However, there may be some longer computing
lessons where teachers will need to introduce postural
changes by having children get up and perform a
different activity. Developing good task variety habits
at a young age in school and home will assist in the
maintenance of these habits into adulthood. It is
anticipated that it will be challenging for parents and
children to learn and maintain good task variety habits
at home, as data show prolonged durations of
sustained computer use are more common at home
(Harris et al. submitted).
2.1.2. Encourage use of active input devices where
possible
Active input technology is a relatively recent introduc-
tion to the computer/electronic game arena, whereby
users interact with a computer through gross motor
movements. These movements are registered by
devices such as a USB camera (e.g. Eye-Toy, Sony),
‘dance mat’, which responds to foot pressures (Dance
Dance Revolution; Konami, Tokyo, Japan) or a hand-
held wireless accelerometer-based controller (Wii;
Nintendo Co. Ltd., Kyoto, Japan). Such devices
encourage less sedentary interaction with the computer
or electronic game and therefore are thought to offer
health advantages over traditional inputs devices such
as joystick controllers, mouse or keypad.
A few recent studies have examined the metabolic
effects of active input devices in comparison to
sedentary activities such as watching television or
playing traditional computer games (Lanningham-
Foster et al.2006,Graveset al.2007,Maddisonet al.
2007, Straker and Abbott 2007). Increasing the
metabolic load, over the resting level, varies depending
upon the input device and games being played. Both
the EyeToy and dance mat can elicit substantial
increases in energy expenditure, levels consistent with
moderate intensity sporting activities such as jogging
and basketball. However, sensible usage patterns and
rest breaks are required as extremely intensive use has
elicited acute pain such as the case of ‘Wii-itis’ reported
by Bonis (2007). Despite this risk, the use of these
devices in preference to traditional computer game
input devices may be beneficial. A pilot study has
found that access to traditional sedentary electronic
game devices decreases physical activity over the week,
but that access to only active input electronic game
devices can increase weekly physical activity (Straker
et al. 2008e).
Based on the available evidence, it is recommended
that children should use active input devices whenever
possible.
Nearly all of the active input applications for
children to date have been games. However,
educational programs could also adopt this technology
and this may be particularly effective for children who
learn well when being active. Encouraging children to
switch from a sedentary electronic game to an active
electronic game may be easier for parents than not
allowing children to play electronic games. Schools
could encourage this by providing active electronic
game alternatives and adopting active input learning
programs when these become available.
2.1.3. Encourage postural variety
The National Institute for Occupational Safety and
Health in the United States of America reviewed the
literature on health effects associated with
occupational work and concluded that there was
strong evidence for an association between static or
specific postures of the neck or neck/shoulder and
MSDs in these regions (Bernard 1997). Whilst high
wrist velocities and accelerations have been reported
during keyboard work (Dennerlein and Johnson
2006b), computer tasks generally require a low level of
effort (Dennerlein and Johnson 2006a, Johnson and
Blackstone 2007) and little movement (Straker et al.
2008c). For example, when a computer-based task was
compared to a book/paper-based task, average
postures and minimal levels of muscle activity were
greater in the computer-based tasks, for both adults
(Wærsted and Westgaard 1997, Straker et al. 2009c)
Ergonomics 461
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and children (Ciccarelli et al.2006,Strakeret al.2008c,
2009d). It is therefore important to encourage postural
variation during computer tasks.
Children tend to have more postural and muscle
activity variation than adults performing an identical
computer task (Johnson and Blackstone 2007, Maslen
and Straker 2009). This may be related to their smaller
size – if using input devices designed for adults, for
example, a greater relative excursion of the fingers or
forearm may be required to move the cursor a specific
distance or move between specific keys, compared to
the movement for a larger, adult upper limb. Children
(5–8 years old) using an adult-sized mouse or keyboard
were found to have greater mean ulnar deviation
and less wrist extension than their same-sex parent
(Blackstone et al.2008).Theyalsohadnearlytwicethe
range of motion during mouse use and three times the
range during typing for both wrist flexion/extension
and ulnar deviation.
The greater postural variation exhibited by children
during computer tasks may also be related to computer
experience – more years of computer use by adults may
lead to more efficient keyboarding and/or mouse skills.
Other factors such as learning and increased coordina-
tion and motor control may also be involved.
Regardless of the cause, it is suggested that adults
should not discourage, and actually promote, children
to move around/‘fidget’ during computer use.
It is also important to recognise that there is large
individual variation in movement patterns. Observa-
tions of children in a classroom situation revealed that
some children moved continuously while others had
very static postures (Murphy et al.2004).Thesemore
static postures were associated with neck and upper
back pain. Large inter-individual variation in load for
agiventaskisalsoinherentforadultpopulations
(Westgaard 2000). Associations between static muscle
activity and pain/discomfort have also been reported
for adults (Jensen et al.1993,Veierstedet al.1993,
Hagg and A
˚stro
¨m1997)andsymptomaticoffice
workers show differences in motor control to their
asymptomatic colleagues (Szeto et al. 2009).
Computer use duration in children increases with
age. When children start to use computers, ergono-
mists, health professionals, teachers and parents
should teach them the importance of periodically
altering their posture and reducing their time spent in
static postures. This may be particularly influential in
maintaining their musculoskeletal health as they grow
and mature into adults. In a study of nearly 900
Australian adolescents, the amount of computer use
(hours per week) was related to habitual sitting posture
(i.e. posture when not using a computer), with
increased head, neck and thorax flexion during usual
sitting related to a greater ‘dose’ of computer use
(Straker et al. 2006c). This study highlights the
importance of developing appropriate guidelines for
younger computer users in order to minimise
musculoskeletal problems for future generations.
Workstations influence posture and postural options
and should therefore be designed to encourage variety.
Based on the available evidence, it is recommended
that children should be encouraged to move around
and periodically alter their posture whilst using
computers. Their computer workstations at home and
school should be designed to promote a variety of
working postures (see below).
2.1.4. Limit sedentary leisure use of computers and
encourage children to engage in other non-sedentary
activities
Two categories of evidence are pertinent to this
guideline: 1) what computer use does physically to the
child; 2) what activities the child may be missing out on
while spending extended periods on the computer.
With regard to computer use displacing physical
activity and the associated health risks, the evidence is
weak for children overall. Studies of the relationship
between obesity and computer use have generally
demonstrated either no relationship (Wake et al. 2003,
Janssen et al.2005,Burkeet al. 2006) or a partial effect
(Kautiainen et al. 2005, Lajunen et al. 2007). The
association between the duration of computer use and
body mass fat percentage is different from the pattern
associated with television watching. In addition, the
association between computer use and decreased
physical capacity also appears to be weak. Many
children are able to combine moderate to high levels of
computer use with physical activity at least equivalent
to that undertaken by children who use computers less
(Ho and Lee 2001, Olds et al. 2004, Mutunga et al.
2006). However, for some children, computer use has
been shown to limit physical activity. Straker et al.
(2006d) found a negative relationship between
computer use and vigorous physical activity on
weekends for 5-year old children. Attewell et al. (2003)
found that children who spent less than 8 h per week
using a computer did not differ from non-users in time
spent playing sport. However, heavier users spent 3 h
less per week on sport and outdoor activities than
non-users. Increasing computer-based sedentary
activities has been identified as a serious health risk for
adults (European Agency for Health and Safety at
Work 2005, Straker and Mathiassen 2009) and
encouraging sufficient non-sedentary activity for young
people is likely to be an important health policy.
Whilst computer use has the potential to displace
some physical activity, adverse musculoskeletal
462 L. Straker et al.
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consequences in adults, as a result of prolonged or
intensive computer use, indicate that it may be wise to
limit the amount of time children spend using a
computer. Pain and musculoskeletal discomfort in
children, teenagers and adults has been shown to be
related to the duration of computer use (Berqvist et al.
1995, Blatter and Bongers 2002, Gerr et al. 2006,
Gillespie et al.2006,Hakalaet al. 2006, Chang et al.
2007, Ijmker et al.2007,JacobsandBaker2002,
Marcus et al.2002).Theproblemmaybeexacerbated
for children because they tend to use computers at
workstations that are not suitable for their
morphology (Oates et al. 1998, Zandvliet and Straker
2001, Dockrell et al.2007).Inaddition,sincechildren
are still developing in terms of spinal posture,
musculoskeletal system and lifestyle habits, there is
concern that patterns of computer use in childhood
could affect the individual in adulthood.
The body of research evidence is increasing and
showing that documented musculoskeletal problems
found in intensive adult computer users are now
occurring in children. The evidence from adult
computer users shows an increased risk for developing
musculoskeletal symptoms when computer use exceeds
4h per day. However, for children, it is difficult to
pinpoint a safe threshold beyond which symptoms,
disorders or physical fitness decrements may occur.
Hakala et al. (2006), using a self-report survey in
adolescents, demonstrated that 2–3 h of computer use
per day posed an increased risk for neck and shoulder
pain and more than 5 h per day was a threshold for
lower back pain. A recent campaign in Western
Australia, entitled ‘Unplug þPlay’ (http://www.heart
foundation.org.au/Healthy_Living/Kids/Parents’_Re
sources/Unplug_and_Play.htm), recommended that
children spend no more than 2 h per day using
screen-based entertainment (computers, TVs, gaming
devices, mobile phones, etc.) for entertainment
purposes (i.e. excluding school homework). This
campaign is supported by a number of health-related
bodies relating to cardiovascular health, diabetes and
cancer and is an expression of the level of concern
that authorities have for children and the increasing
use of screen-based entertainment.
Based on the available evidence, it is recommended that
children’s use of sedentary screen-based media (compu-
ters, TVs, gaming devices, mobile phones, etc.) for leisure
purposes should be limited to a maximum of 2 h per day.
2.2. Encourage reasonable postures during sedentary
tasks
Whilst the first few guidelines limit the total duration
and prolonged uninterrupted periods of sedentary
computing tasks, the next few guidelines concern the
maintenance of appropriate postures when performing
these tasks.
Cook and Burgess-Limerick (2003) noted that there
is a consensus developing that there is not one ideal
posture or set-up for computer workstations, but
rather that users should be guided to use a range of
suitable postures throughout the day. Computer use
involves both physical and visual interaction and these
tend to determine the postures assumed. The design of
the workstation chair, desk, display and control
equipment is thus critical to encourage appropriate
interactions and postures.
2.2.1. Encourage a range of suitable postures through
appropriate workstation design
Specific workstation dimensions and parameters have
been shown to affect posture, muscle activity and
musculoskeletal discomfort or disorders in both adults
and children. Research describing chair, desk, display
and input devices will be reviewed individually in the
following sections. The current workstation situation
for children using computers is described below. This
description primarily pertains to school settings as
there is little research detailing home computer
workstations for children despite evidence that home
use is often considerably greater.
There is little doubt that children at school
frequently use furniture that is not suited to their
anthropometry. A number of studies from many
different countries have shown discrepancies between
children’s anthropometry and the chairs and desks that
are available at school (e.g. Milanese and Grimmer
2004 – Australia, Parcells et al.1999–USA,
Panagiotopoulou et al. 2004 – Greece, Savanur et al.
2007 – India).
One of the first studies to highlight the disparity
between computer workstations and children’s
morphology was that of Oates et al. (1998). Of 95
children aged between 8 and 12 years, Rapid upper
limb assessment (RULA) ratings indicated that no
child was working in an acceptable postural range. The
sample for this study included approximately equal
numbers of children from the 5th, 50th and 95th
percentiles for stature, which effectively means that
two-thirds of the sample were at the extremes of
anthropometry for their age; however, the results of
this study are still a cause for serious concern. More
than half of the computer displays were at a height that
exceeded recommendations for adult users and none of
the computer workstations observed was adjustable.
The chair dimensions were ‘marginally adequate’,
although children were still sitting with the feet
unsupported, and the height adjustability of the chair
was lacking. Kelly et al.(2009)foundsimilarresultsin
Ergonomics 463
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asampleof40IrishschoolchildrenandZandvlietand
Straker (2001) found that schools in Canada and
Australia were rated highly in terms of the capability
of the computer hardware, but the ratings of the
workstation and visual environment faired poorly.
A total of 200 Japanese schools were surveyed with
somewhat better results. Height-adjustable desks were
seldom used in any of the schools; however, although
not prevalent in elementary schools, height-adjustable
chairs were common in junior high and high schools
(Sotoyama et al. 2002). In contrast, Noro et al. (1997)
found a large mismatch between Japanese primary
school children and their computer workstations.
Szeto (2003) reported that in Hong Kong school
computer displays were commonly placed on top of the
central processing unit, due to limited space avail-
ability, and chairs were non-adjustable. Even if
different sizes of school furniture are available, schools
may not always distribute them appropriately. Bennett
(2002) reported that although three sizes of chair were
available in a Californian school, some of the younger
classes had only the largest chairs; conversely, some of
the older classes had only medium size chairs.
Only limited data are available regarding work-
station set-up for children using computers in the
home. Jacobs and Baker (2002) found that children
from the USA generally used computers at home on
furniture that was not designed for computer use, with
86% of the sample reporting that their heels did not
touch the ground while using the computer. There was
a trend for a relationship between self-reported
musculoskeletal discomfort and using furniture that
was not designed for computer use. Keyboard and
display placement were also poor. Space limitations for
Hong Kong children at home were reported to limit
the availability of a computer desk in some households
(Szeto 2003) and most households shared a computer
between children and adults. This latter situation is
likely to be the usual scenario for many children
throughout the world. Roberts et al.(2005)reported
that 31% of children in the USA had a computer in
their bedroom and a further 12% had their own
notebook computer. This indicates that over half of
the children share a computer with their family,
probably on an adult-sized workstation.
Molenbroek et al. (2003) described various ways in
which furniture can be fitted to the end user. In a
school environment, the most common approach, to
minimise cost, is to provide fixed height, non-
adjustable furniture of various sizes. Ideally, for
computer workstations used by a wide age range of
children, it would be preferable for schools to provide
adjustable furniture. Simple, practical and cost-effec-
tive adjustable furniture solutions have been shown to
reduce musculoskeletal discomfort in adult users
(Mekhora et al. 2000). In 4–17 year old children,
workstation adjustment to match the stature of the
individual child was shown to promote more neutral
head postures (Straker et al. 2002). In addition, Laeser
et al. (1998) demonstrated that a workstation set-up
that was adjusted to suit the anthropometry of
individual children improved RULA scores. The
importance of correctly configuring workstations to
encourage beneficial postures is therefore well
established.
The definition of what constitutes a good seated
posture is the subject of some debate. However, rather
than just the traditional seated posture with an upright
trunk and thighs perpendicular to the trunk (see review
by Corlett 2006), an array of seated postures is now
considered acceptable, including forward and
backward inclined positions (Mandal 1982, Nag et al.
2008). In a review of guidelines for adult computer
workstations, Cook and Burgess-Limerick (2003)
concluded that the array of seated postures that can be
adopted (back-leaning, upright, forward-leaning) each
have specific advantages and disadvantages, and an
ability to vary postures and easily adjust furniture to
facilitate a range of postures was desirable. This range
of furniture adjustability with a continuum of seated
posture options is likely to apply to the workstations of
children.
Standing-only workstations are related to increased
musculoskeletal discomfort with prolonged use,
whereas workstations that allow sitting and standing
have been shown to reduce musculoskeletal discomfort
in adults (Roelofs and Straker 2002). Standing
computer workstations for short duration tasks may
therefore be suitable for children. Aside from being
seated at a desk, children can use computers standing
and with notebook computers sitting on floor/bed and
lying (see section 1.2.6).
Recently, active workstations (where computer use
is performed whilst the person walks slowly on a
treadmill or cycles slowly on an exercise bike) have
been advocated for adult office workers as a way of
increasing non-exercise physical activity and the
subsequent health benefits (Levine and Miller 2007,
Thompson et al. 2008, Straker and Mathiassen 2009).
Whilst a small typing and slightly larger mousing
performance decrement has been measured during the
use of these workstations, this performance loss is
probably outweighed by the health gains (Straker et al.
2009b). No studies on children using these active
computer workstations have yet been reported.
Based on the available evidence, it is recommended
that school computer workstations should be
adaptable in order to accommodate the size ranges of
the children using them. Computer workstations used
in the home should match the size and shape of the
464 L. Straker et al.
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child. All computer workstations should support a
range of reasonable postures. Standing and sitting
workstations should be used.
2.2.2. Encourage a range of suitable seated postures
through appropriate chair selection and adjustment
Selection and adjustment of an appropriate chair for
computer-based work is an important component of
workstation optimisation. Associations between sitting
postures and spinal pain or discomfort have been
described for both adults and children (Trevelyan and
Legg 2006). Whilst there is general agreement that the
feet should be able to be positioned flat on the floor
during seated work, there is less consensus regarding
factors such as seat slope, the orientation and use of a
backrest and the presence of armrests on the chair.
Mismatches between children’s anthropometry and
school chairs have been widely reported (Parcells et al.
1999, Legg et al. 2003, Milanese and Grimmer 2004,
Gouvali and Boudolos 2006, Murphy et al.2007,
Saarni et al. 2007, Savanur et al.2007).Corlett’s(2006)
review of research-based seating requirements for
workplaces and schools noted that school furniture
was inadequate as a result of decisions not related to
what pupils needed. Some studies (e.g. Milanese and
Grimmer 2004) have found chairs to be too low, others
too high (Parcells et al.1999,Panagiotopoulouet al.
2004, Gouvali and Boudolos 2006, Chung and Wong
2007, Savanur et al.2007)andSaarniet al.(2007)
reported that chairs in Finnish schools were too high if
compared to a European standard, but too low in
relation to individual anthropometric measures. Mo-
lenbroek et al.(2003)comparedthefitofschoolchairs
based on popliteal height to that based on stature and
concluded that the selection of chairs based on stature
can result in a misfit of up to 7 cm in chair height.
The recommendation that the height of the front of
the seat pan should correspond fairly closely to the
(shod) popliteal height is perhaps the least controver-
sial aspect of seating ergonomics. Popliteal height has
been postulated to be the most relevant dimension for
seat selection (Barrero and Hedge 2002). This position
enables the individual to support the feet flat on the
floor and reduces pressure on the back of the thighs
(Pheasant 1996, Parcells et al.1999,Milaneseand
Grimmer 2004). Some of the load due to body weight
is transmitted through the feet while sitting (Nag et al.
2008), thereby reducing the load that is transmitted to
the seat pan under the buttocks. In what appears to be
the sole study of children’s home computer work-
stations, self-reported pain was inversely related to
reporting that the feet were positioned flat on the floor
(Jacobs et al.2006).Itisrecommendedthattheseat
pan height allows the child’s feet to be flat on the floor.
Should children use backrests? In an experimental
setting, the use of backrests on a chair has been shown to
reduce the load distributed at the seat (Nag et al.2008)
and is thereby thought to reduce spinal loading. Leaning
against a backrest can also assist with the retention of
the lumbar curve during sitting (Corlett 2006). Seated
postures without a backrest have been reported to
increase load within the spinal discs to a level that may
restrict nourishing of the disc in adults (Colombini et al.
1986). However, observations of children working at
school have shown that children often work without
using a backrest, even if one is present (Murphy et al.
2004, Ciccarelli et al.2006,Breenet al.2007).In
addition, children who used a saddle-style seat with no
backrest for 2 years were found to have improved trunk
muscle strength, better sitting and standing postures and
less musculoskeletal discomfort than a control group
who used traditional school chairs with backrests
(Koskelo et al.2007).Breenet al.(2007)alsoreported
that children who did not have a backrest tended to
adopt better postures than those with a backrest.
Geldhof et al.(2007)reportedthat8–12yearold
children used a backrest for 36% of the time and Cardon
et al.(2004)observedbackrestsittingfor30%ofthe
lesson time. It is likely that the fit of furniture to the
individual’s anatomy is influential in the use of
backrests – seat pan depth is a parameter that has been
reported often to be mismatched to children’s
morphology for school furniture (Parcells et al.1999,
Milanese and Grimmer 2004, Panagiotopoulou et al.
2004, Savanur et al.2007).Aseatpanthatistoolong
suggests that the child would not comfortably be able to
lean back against the backrest without causing pressure
behind the knees or slumping.
Astudyofthebuttockcontoursofseated16–17
year old Australian students revealed a significant
difference between the sitting posture assumed whilst
typing and sitting back against the backrest (Tuttle
et al. 2007). Switching between these positions may
occur when typing then reading from the screen or
looking at a teacher or a display board and suggests
some benefit for postural variation. A study of
prolonged (2 h) sitting for young adults prompted the
recommendation that chair design should allow
individuals to vary postures easily, rather than
constraining posture to an assumed ideal posture
(Callaghan and McGill 2001). Whilst it appears that a
suitable backrest can reduce loading on the lower
trunk, a chair without a backrest may encourage more
trunk activity and general movement (Cardon et al.
2004). If a backrest is present on the chair, it should be
adjustable in both horizontal and vertical directions.
Similarly to backrests, armrests on chairs have been
shown to reduce loading through the seat pan during
sitting for adults (Nag et al. 2008). The presence of
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armrests on chairs has been associated with a lower
risk of neck and shoulder disorders in a prospective
study of newly employed computer users (Marcus et al.
2002). Forearm support during computer work is
known to be of benefit in reducing musculoskeletal
stress and this will be discussed in the section relating
to computer desks. Delisle et al.(2006a)suggestedthat
alternating forearm support from the desk surface and
from chair armrests could be of benefit by introducing
postural variation. However, the use of armrests for
children’s seating has not received any scientific
investigation, hence their efficacy and ideal
positioning with reference to body dimensions is
unknown. Fixed armrests that are too big or too
high could be expected to constrain posture,
particularly that of the upper limb, and may prohibit
the chair being positioned close enough to the table to
permit forearm support on the desk and allow for the
child’s smaller reach when using input devices.
Armrests also need to be adjustable anteriorly and
posteriorly and laterally as well as in height to ensure
an appropriate position to provide support. Whilst it is
likely that armrests that are at an optimal position may
provide the benefits that are documented for adults,
given the difficulty in ensuring an appropriate armrest
position, it may be wiser to provide chairs without
armrests. This may have the additional advantage of
allowing greater postural variability.
Seating intervention studies have been conducted to
determine whether different styles of chairs offer any
advantage to traditional chairs. There have been some
promising results, including those of a Finnish study by
Koskelo et al.(2007).Thisstudyincludedacontrol
group, who continued to use traditional, non-adjustable
furniture, and an experimental group, who received
adjustable tables and adjustable, saddle-type chairs that
had no backrest and encouraged a more open angle of
the hip, in line with Mandal’s (1982) recommendations.
At the end of the 2-year study, the experimental group
had better sitting and standing spinal postures, greater
trunk muscle strength and fewer reports of discomfort.
Whilst these results are encouraging, limitations of this
study include the small sample size (15 matched pairs)
and the inability to extract separate effects of sloping
desk, adjustable furniture and saddle-style of seat. In
another study of the benefits of alternative seating,
Linton et al. (1994) observed that students using newer
furniture had fewer reports of discomfort but differences
in actual sitting postures were small and the children did
not automatically sit ‘properly’ with the new furniture.
Whilst new seat designs may offer some promise, the
current body of evidence is not sufficient to inform
specific recommendations.
Schools are in an extremely difficult position when
it comes to providing appropriately sized seating for
computer (and traditional school work) tasks. Garcia-
Acosta and Lange-Morales (2007) recently attempted
to define chair sizes for Colombian school children
aged from 5 to 18 years. In order to minimise costs it
was desirable to have as few sizes as possible. Upon
further analysis it was determined that at least five sizes
of furniture were required to encompass the entire age
range and variation between the 5th and 95th
percentiles students. Bennett (2002) has shown that,
even when multiple sizes of school furniture are
available, they may not necessarily be distributed
between classes with ergonomic principles in mind.
Other considerations that may differ between adult
workplaces and those of schools include the range of
ages and sizes that may be required to share one
computing facility, the desirability in some classrooms
for the chairs to be stackable, the need for teachers to
be able to view computer displays and interact with
students and shared use of single computers by two or
more students. Seating requirements are therefore
likely to be considerably more complicated in
educational environments. Whilst better designed
furniture may be desirable, funding is typically limited.
However, the chair is an easily adjustable component
of the workstation set-up and children are expected to
adopt seated postures for much of their ‘working’ day.
Chair size, therefore, should suit the child’s size – if this
cannot be done through the purchase of adjustable
furniture, basic improvements in seating position may
be achievable through simple interventions, such as the
provision of footstools to enable the feet to be
supported.
Seating should aim to encourage movement as
much as possible. For computer tasks, the chair should
be able to be placed close to the edge of the desk so
that input devices can be reached and forearm support
can be achieved on the desk surface. Children should
be encouraged to evaluate their sitting position and
take advantage of any adjustability or other supports
just as an adult would check rear-view mirror and seat
position when sitting in a car.
Based on the available evidence, it is recommended
that seat pan height should allow the child’s feet to be
flat on the floor. The lack of a backrest is acceptable to
encourage movement, but if one is provided it should
be adjustable to fit the child’s lumbar spine. Armrests
should be avoided unless they fit the child and desk
well. The seat style should support a range of
reasonable postures.
2.2.3. Encourage suitable postures by selecting and
adjusting an appropriate work surface
Desks can enable the user to sit in a range of
comfortable postures, with enough space for input
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devices and documents and sufficient depth for
positioning the computer display. In school situations
the desk may also have to accommodate two or more
users simultaneously. Throughout the working day,
school computer desks may also have to accommodate
children of substantially different sizes. Desks also
need to accommodate both computer and paper-based
tasks.
The benefits of being able to support the forearms
during computer work have been demonstrated for
both adult and child populations. Supporting the
forearms on the desk surface or on chair armrests
has been shown to reduce muscle activity during
computer use (Aaras et al.1997,Karlqvistet al. 1999,
Woods et al. 2002, Straker et al.2008d).Theuseof
support also results in reduced discomfort and
musculoskeletal symptoms (Bergqvist et al.1995,
Aaras et al. 1998, Marcus et al. 2002, Woods et al.
2002, Korhonen et al.2003,CookandBurgess-
Limerick 2004, Rempel et al.2006).Inareviewof
the health consequences of computer work Aaras et al.
(2000) concluded that supporting the whole forearms
was of fundamental importance for reducing muscle
load and musculoskeletal pain. It should be noted that
studies have not been universal in supporting the
efficacy of forearm support. In a study by Cook and
Burgess-Limerick (2004), 15% of participants with-
drew from the forearm support condition because of
discomfort or dissatisfaction with this work position
due to large abdomens. Delisle et al. (2006b) concluded
that forearm support may be beneficial for the neck
and shoulder to the detriment of the wrist and forearm.
However, the body of evidence seems to strongly
support the benefits of the provision of a supporting
surface for the forearms. In addition, the efficacy of
forearm support during computer use has been
specifically shown to be effective for children by
Straker et al. (2009b). Muscle activity reductions in
this study were of a sufficient magnitude to be clinically
meaningful.
Forearm support can be provided by moving the
keyboard away from the edge of the desk, from chair
armrests and from specific support devices that are
attached to the chair or desk. Rempel et al. (2006)
found a reduced incidence of discomfort and pain for
call-centre operators who used a forearm support.
Cook and Burgess-Limerick (2003) suggested that a
curved or shaped work surface may provide the best
support. However, forearm support can also be
obtained on a straight desk by simply moving the
keyboard *12cm away from the edge of the desk
(Marcus et al. 2002). It is recommended that a straight
desk has the keyboard and mouse positioned far
enough away from the front edge of the desk so that
the forearms can be supported.
In order to provide forearm support without
compromising spinal posture, Cook and Burgess-
Limerick (2003) noted a general consensus for the desk
height to be at or slightly below the elbow height of the
seated operator. While an adjustable height desk may
be of benefit to achieve this height initially, it may be
feasible and cheaper in school and home settings to
manipulate the seated height of the child to suit the
desk height, using an adjustable chair or firm cushions
(bearing in mind any fire safety regulations) to adjust
chair height and a footrest to support the feet when
needed.
The desk surface area needs to be large enough
to enable forearm support and appropriate keyboard
and mouse configuration. The desk needs to be of
appropriate depth to permit placement of the display
at a sufficient distance to enable visual comfort (see
section 1.2.5). There is also nearly always a need for
space for documents and other working materials. It
is appreciated that schools have limited space and
there may be pressure to provide as many
workstations as possible. However, insufficient space
on the surface of the computer workstation may lead
to poor working postures and poor productivity.
One form of ‘space-saving’ configuration is the use
of pull-out keyboard trays or multiple-level desks.
These may constrain the available working postures by
restricting the potential placements of input devices
(Cook and Burgess-Limerick 2003). Computer
workstations whereby the mouse and keyboard are at
different heights may result in less neutral postures and
greater muscle activity (Dennerlein and Johnson
2006b). Pull-out keyboard trays may be a particularly
poor choice for younger computer users because their
smaller reach would make it difficult to access
documents or controls on the desk surface. In addition,
if children are required to share a school computer, a
keyboard tray may restrict input for one of the users.
Keyboard trays and their adjustment mechanisms can
also constitute a hazard to the knees or thighs if they
are located under the desk surface (Cook and Burgess-
Limerick 2003).
Sloped desks have been shown to be effective in
bringing children’s posture into a more beneficial
alignment for written tasks (Marschall et al.1995,
Koskelo et al.2007)inaccordancewiththe
recommendations of Mandal (1982). However, a
sloping desk is not likely to be practical for
typical computer-based work as the keyboard,
mouse and other materials may slide offthe desk.
Document holders for hard copy documents and
inclined supports for books can reduce head and
neck flexion. Positioning paper material close to
the computer display can reduce head and neck
rotation.
Ergonomics 467
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Based on the available evidence, it is recommended
that the desk should allow forearm support, be
adjusted to about sitting elbow height and be a single
thin surface of reasonable size.
2.2.4. Encourage appropriate postures and gaze angle
by positioning computer display appropriately
The appropriate positioning of a computer display
requires attention to both visual and musculoskeletal
concerns, with a combination of spinal posture and eye
gaze angle determining how the target is viewed (Aara
˚s
et al.1997,Mon-Williamset al.1999,Burgess-
Limerick et al.2000,Psihogioset al. 2001, Sommerich
et al. 2001).
Existing guidelines defining display heights for
adults generally recommend the top of the viewing
area of the display be placed in a range between eye
level and 40–608below eye level (for example,
Australian Standard 3590.2; Canadian Can/CSA-
Z412-M89; European ISO-9241; ANSI/HFES 100.
2007) (see Straker et al. 2009e for review). This broad
range of recommendations persists in spite of
considerable research, perhaps because of the large
intra-individual differences in the relationship of
musculoskeletal and visual systems (Burgess-Limerick
et al.1998,Mon-Williamset al.1999,Strakerand
Mekhora 2000). Differences in methods may also
contribute to the wide range of recommendations in
the literature – for example, it is not always stated
whether the viewing angle is measured in relation to
the centre or the top of the display.
If the display is placed such that the top of the
viewing area of the display is at eye level, the posture of
the head and neck will be more upright and cervical
erector spinae activity will likely be lower, but this
position may be more stressful for the visual system
(Jaschinski et al.1998).Lowermonitorplacementsare
associated with greater head and neck flexion, which
could be considered more stressful on the neck and
shoulder muscles with higher muscle activity levels as
the consequence (Straker et al. 2008a). However,
research evidence suggests that this is not generally
the case. Epidemiological studies show fewer reports of
musculoskeletal discomfort associated with lower dis-
play heights (Marcus et al.2002,Fostervoldet al.
2006) and these lower display angles correspond more
closely to visual preferences (viewing angles of 9–108
below the horizontal (Psihogios et al. 2001, Sommerich
et al. 2001)). Trapezius muscle load is an important
consideration as it is a large muscle and a common site
of discomfort in computer users (Bergqvist et al. 1995).
Working with head and neck flexion will likely increase
cervical erector spinae muscle activity (Villanueva et al.
1997, Turville et al. 1998, Sommerich et al. 2001, Greig
et al. 2005). However, trapezius activity may be
unaffected (Aaras et al. 1997, Villanueva et al.1997,
Sommerich et al.2001,Fostervoldet al.2006)ormay
even be reduced for lower viewing angles (Turville
et al.1998,Greiget al.2005).Trapeziusmuscleactivity
has been shown to be relatively constant across a range
of viewing angles in both adults (Turville et al. 1998,
Fostervold et al. 2006, Straker et al. 2009e) and
children (Straker et al. 2008a). Gaze angles above the
horizontal (the top of the viewing area of the display
positioned above eye level) may increase strain on deep
subcapital muscles (Straker et al.2009e)buthavebeen,
rarely, recommended. The practice of placing the
computer display on top of the central processing unit
is not recommended. This workstation configuration
has been observed in school settings in several
countries (Noro et al. 1997, Szeto 2003, Straker et al.
2008a) and is likely to promote an upward gaze angle
and unwanted increases in muscle activity, particularly
in smaller children.
In summary, evidence relating to viewing angles
generally supports display positions that promote a
downward gaze angle. In accordance with this, Cook
and Burgess-Limerick (2003) recommend that
workstations should permit adjustment of display
height so that downward viewing angles between 08
and 458are possible. However, there appears to be no
specific angle within this range that has particularly
advantages (Burgess-Limerick et al. 1998). Marked
inter-individual variability in gaze angle preference
(Burgess-Limerick et al. 1998) and the interaction of
musculoskeletal and visual systems (Mon-Williams
et al. 1999) exists.
Given the similarity of responses to changes in
display height between adults and children (see Straker
et al. 2008a,b, 2009e, Maslen and Straker 2009), it
seems reasonable that similar display placement
recommendations may be appropriate for children. It
is recommended that children start with the top of the
display at sitting eye height and be able to adjust this
lower if required for comfort.
The appropriate distance to the computer display
depends on age, visual capacity, viewing angle (the
display can be placed closer if it is lower) and the
clarity and size of the image or text (Cook and
Burgess-Limerick 2003, Rempel et al. 2007b).
Preferred viewing distances, measured from the eye to
the centre of the computer display, range between 50
and 100 cm (Jaschinski et al.1998,Dellemanand
Berndsen 2002, Shieh and Lee 2007) for adults. No
studies could be found that have investigated optimal
viewing distances for children. It is recommended that
the display is positioned at approximately arm’s length
as a ‘user-friendly’ starting point, which can be
modified by children themselves to comfort.
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Neck or head rotation away from the midline has
been linked to increased discomfort or musculoskeletal
symptoms among computer users (van den Heuvel
et al. 2006, Szeto and Sham 2008). For adults, if the
computer display is the primary visual target, it should
be positioned directly in front of the user (Cook and
Burgess-Limerick 2003). In situations where children
share a single computer it is obviously not possible to
place the display directly in front of all children. In this
situation it is of particular importance that the
computer display is placed at a greater viewing
distance, as a near display will create more extreme
viewing angles for those not directly in front of the
screen. Exchanging places among the users during long
computer use sessions may also provide some protec-
tion against discomfort. For single child use it is
recommended that the display be positioned directly in
front.
Lighting and glare can be sources of visual
discomfort during computer use. Placing the computer
display perpendicular to windows, using indirect
lighting sources, window treatments and anti-glare
screens can all be used to limit glare (Cook and
Burgess-Limerick 2003, Anshel 2007), although mesh
anti-glare screens are not recommended (Anshel 2007).
An association between fewer reports of discomfort
and reporting that the display was free from glare was
found in a study of home computer use by children
(Jacobs et al.2006).Itisrecommendedthatchildrenbe
taught to identify glare and adjust their workstation to
avoid it.
The display technology may influence clarity,
stability and adjustability of the display. Older style
cathode ray tube displays are currently being replaced
in many adult and child workstations with thin film
transistor (or LCD) displays. These thinner and lighter
weight displays provide for greater flexibility of
positioning and may have a clearer, more stable image.
It is recommended that a good quality display with
good contrast be used and be free of flicker.
Based on the available evidence, it is recommended
that computer displays should be placed so that the top
of the display is at or below eye height, at about arm’s
length away and directly in front of the user. Work-
station orientation should minimise glare. A good
quality display with a clear stable image should be
used.
2.2.5. Encourage appropriate postures by selecting and
positioning keyboard and pointing device appropriately
The keyboard and mouse are currently the most
common computer input devices; however, other
pointing devices, such as touchpads, trackballs, joy-
sticks, and optical pens are used (Woods et al.2002,
Cook and Burgess-Limerick 2003). Only limited data
are available characterising the usage of different input
devices by children, but the mouse appears to be the
most common pointing device used by children both at
home (Burke and Peper 2002) and at school (Sotoyama
et al. 2002).
Research has shown that young children can learn
to use a mouse easily (see review by Barrero and Hedge
2002, Donker and Reitsma 2007). However, mouse use
has been associated with pain in schoolchildren (Breen
et al.2007),asithasinadults(Jensenet al.2002),soit
is important to optimise the size, button activation
force and location of the mouse on the desk.
There is only limited research evaluating mouse size
and children’s anthropometry. An interesting study by
Blackstone et al. (2008) compared the use of input
devices by 14 children aged 5–8 years and their same-
sex biological parent. Subjects used standard and
smaller-sized keyboards and mice. When using the
standard mouse the children had 188more ulnar
deviation and 98less wrist extension than their parents.
They also had twice as large a range of motion in both
wrist flexion/extension and ulnar/radial deviation.
Children had to reach around the keyboard to access
the mouse and access the mouse buttons from the side
rather than from the top of the mouse because it was
too big for their hands. When children used the smaller
mouse, there was a significant reduction in ulnar
deviation and a decrease in muscle activity. Better
performance (fewer errors and faster movement times)
was also associated with the smaller mouse. Children
had to use proportionally more force than adults to
operate the mouse buttons and these authors
recommended that both the mouse button activation
force and the physical size of input devices be designed
for children. It is recommended that mouse size be
appropriate to the child’s hand size.
Due to a lack of research, no recommendations can
be made regarding the necessity of providing a mouse
specifically shaped for left-handers. While it appears
that most adults can adapt to right-handed mouse use
(Woods et al. 2002), it cannot be assumed that this is
the case for all left-handed individuals, including
children. It is recommended that a symmetrical mouse
be used as this would permit the greatest flexibility in a
situation where multiple users are required to use the
same computer. A study of computer use by British
adults revealed that even left-handed adults tended to
use the mouse with their right hand (Woods et al.
2002). It is unknown whether this also applies to
children; hence, it is recommended that workstations
enable mouse use on either side of the keyboard.
An extension of this flexibility arises from research
conducted by Delisle et al. (2004), in line with
principles proposed initially by Cook and Kothiyal
Ergonomics 469
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(1998). Right-handed, adult computer users were
trained to use a mouse with their left hand. A total
of 16 of the 27 participants fully converted to left-
handed mouse use within 1 month. Posture was
significantly improved when using the mouse with the
left hand, as right-handed use required greater
deviation of the upper limb in order to bypass the
number pad on the right side of the keyboard.
Recommendations that a keyboard without number
pad is used when practical have been put forward by a
number of authors, as discussed in the following
paragraphs. However if this is not practical, left-
handed mouse use might constitute an effective
alternative. Young children may be particularly
adaptable in this regard.
Apanelof21‘experts’assessedseveralnon-
keyboard input devices for adult use in a study by
Woods et al.(2002).Therewerewideindividual
differences in preference, although the traditional
mouse was the most favoured overall. The shape of
the device was important for comfort, which suggests
that smaller devices may be more appropriate for
young children, in line with the results of Blackstone
et al.(2008).Operationofsometrackballswasdifficult
because the ball was too large for the adult users and it
was reported that the fingers had to be held above the
trackball in order to prevent accidental activation. In
line with this report, and given the importance of
forearm support as discussed in section 1.2.3, the
trackball in its current form may generally not be a
good choice for children.
There is little evidence that alternate keyboard
styles (split, inclined, different shape) generally provide
significant benefits to adult computer users in compar-
ison to standard keyboards in the workplace (Cook
and Burgess-Limerick 2003, Rempel et al.2007a).
Although recent laboratory studies have shown no
performance decrement and improved fatigue and
posture measures in adults (McLoone et al. 2009). A
review of workplace interventions by Brewer et al.
(2006) reported mixed evidence for the effects of
alternative keyboards on musculoskeletal outcomes.
It is likely that some keyboards may be more
appropriate for particular adults but the effect may
be small. There is very limited research addressing
appropriate keyboard designs for children. In the study
by Blackstone et al. (2008) described earlier, there were
no systematic differences in physical exposure mea-
sures between the standard and smaller keyboards, and
only negligible differences in performance. However,
the difference in keyboard size was only marginal, as
more proportionally scaled-down keyboards could not
be found at the time of the study. As per mouse use,
the relative activation force required for key activation
by children was twice that of their parents. It is
recommended that a scaled-down keyboard be
provided for younger children, with small key
activation forces.
Blackstone et al.’s (2008) study also highlighted the
ulnar deviation that was required by young children in
order to access a mouse placed to the side of a standard
keyboard. Reduced muscle activity and more neutral
postures have been reported when a mouse was used in
conjunction with a keyboard without a number pad
(Cook and Kothiyal 1998, Sommerich et al.2002).A
review of musculoskeletal consequences of keyboard
use by Gerr et al. (2006) also concluded that
minimising ulnar deviation may reduce the risk to the
musculoskeletal system. Using a keyboard without a
number pad may therefore be particularly appropriate
for children, with their smaller size and reach. It is
recommended that keyboards without a number pad
be used where possible, permitting a closer position of
the mouse to the midline of the body.
Negative slope keyboards have been recommended
in order to reduce wrist extension (Hedge and Powers
1995) and have been concurrent with improved
postural (RULA) scores in children (Laeser et al.
1998). However, the effects of the negative slope
keyboard in the latter study cannot be extracted from
the alteration of the workstation to suit the child’s
anthropometry, and the change in mouse location, so
there is not yet any definite evidence that tilt-down
keyboards can be of benefit for children. Further, a
specialised tilt-down keyboard tray has other
limitations (see desk section above) and therefore this
is not recommended. From adult studies one can infer,
however, that minimising keyboard thickness, having
the keyboard placed at or below elbow height and
supporting the forearms during keyboard and mouse
use are all beneficial for the musculoskeletal system
(Faucett and Rempel 1994, Aaras et al. 1997, Marcus
et al. 2002, Woods et al. 2002, Cook and Burgess-
Limerick 2003, Gerr et al.2006).Athinkeyboardwith
minimal slope and a clear key activation feel is
recommended. Compared to flat keyboards, keyboards
with a positive slope have been shown to increase wrist
extension (Simoneau et al. 2003) and it is likely that the
new thin keyboards, due to their thickness being more
in proportion to the stature of the smaller children, will
reduce wrist extension.
In summary, research relating specifically to
children’s use of input devices is notable by its scarcity
and the principles that apply to adults have often had
to be extrapolated to children to provide any evidence.
Based on the available evidence, it is recommended
that input devices be placed on the desk surface, with
the keyboard straight in front of the user, but away
from the desk edge in order to take advantage of
forearm support. The mouse should be placed close to
470 L. Straker et al.
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the keyboard and sufficient room should be available
for operation of the mouse. The mouse should be
symmetrical in shape. A thin keyboard, preferably
without numeric pad, should be used. Scaled-down
versions of input devices are recommended for younger
children.
2.3. Encourage appropriate behaviour when using and
transporting notebook computers
The last three guidelines deal with additional issues:
laptop/notebook computer use, touch-typing skill and
early recognition of discomfort.
The mandatory notebook programs implemented
by some schools may have significant ramifications for
children’s musculoskeletal well-being, entailing risk
associated with not only notebook use, but also the
burden carrying the notebook computers to and from
school. However, the perceived need for children to
have notebook computers to use at school and home is
now diminished, given home computer and Internet
access. This enables children to share files at school
and home without the need to transport expensive
computer equipment.
In a study of Australian students aged 10–17 years,
61% of children in such programmes experienced
discomfort carrying their notebooks. The type of note-
book was related to the discomfort, with least discom-
fort associated with the lightest model. Similarly,
Heasman et al.(2000)foundanassociationbetween
weight of a portable computer and musculoskeletal
discomfort in adults. In a study of US children,
musculoskeletal discomfort in several body regions was
also associated with notebook carriage (Sommerich et al.
2007) and there was a trend for discomfort to be related
to the mode of transport (bearing the load with one
shoulder). In contrast, the method of transportation in
adults (Heasman et al.2000)wasreportedtobe
unrelated to the discomfort experienced in any body
region. It had been expected that carrying the notebook
in a backpack, rather than using a shoulder strap,
carrying handle or carrying in a briefcase, would be
associated with less discomfort. It seems wise to err on
the side of caution where children are concerned,
however, and to follow the recommendation by Harris
and Straker (2000). It is recommended that a comfor-
table backpack with two shoulder straps should be used
to transport the notebook. In addition, the weight of the
notebook should be kept to a minimum. Recent
evidence has highlighted that backpacks should not be
perceived as heavy and fatiguing by children and that
walking and cycling to school may be protective
(Haselgrove et al.2008).
Optimisation of posture while using a notebook or
similar sized computer is also important, in accordance
with the principles governing display position and
forearm support described earlier in this paper. Poorer
postures, increased muscle activity, shorter viewing
distances and greater discomfort have all been
associated with the use of notebook computers in
comparison to desktop computers in adults (Saito et al.
1997, Straker et al.1997,HarrisandStraker2000,
Szeto and Lee 2002). Use of a notebook computer was
associated with more static postures in adults
(Sommerich et al. 2002) in comparison to operating the
notebook with an external keyboard and mouse.
Improved neck posture and comfort were also evident
when the external devices were used with the notebook.
Other authors similarly recommend the use of external
input devices and display screens when using small,
mobile computers (Harris and Straker 2000, Heasman
et al. 2000, Berkhout et al.2004).Whenusing
computers with fixed articulation between keyboard
and screen, it may not be possible to optimise both
keyboard access and distance to the display (Straker
et al. 1997). Older children are likely to experience the
same problems when using notebook computers as
adults and are therefore likely to need an external
keyboard. However, smaller children may be able to
adopt reasonable postures, including forearm support
and appropriate viewing angle. It is recommended that
an external keyboard be provided when a child cannot
adopt an appropriate posture with a notebook
computer. Interestingly, tablet-style notebooks have
been found to result in postures and muscle activities
more similar to writing with pen and paper (Straker
et al.2009a).Afurtherissuewithnotebookcomputers
is the use away from desks. Harris and Straker (2000)
found that children reported using notebooks on desks
only 34% of the time. Other postures included lying
prone, floor sitting and sitting with computer on lap.
The portability provides the opportunity for posture
variety, but also for more extreme postures and glare
problems. It is recommended that children are
encouraged to use a range of reasonable postures, but
are taught to avoid extreme postures and be aware of
glare.
Based on the available evidence, it is recommended
that, if required, notebook computers should be
lightweight and carried in a two-strap back pack.
External keyboard and display height adjustment is
likely to be required for larger children. Alternatives to
chair sitting postures should be encouraged as long as
they are reasonable postures.
2.4. Teach children computing skills
According to Delleman and Berndsen (2002), being
able to touch-type offers the advantage that display
height and keyboard position can be optimised
Ergonomics 471
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independently. Given the documented benefits of
forearm support and the effects of display height and
viewing distance on posture and muscle activity (see
sections 1.2.3 and 1.2.4), this scenario may help to
reduce musculoskeletal load. A trend for muscle
activity to be lower for touch-typists (Sommerich
et al.2001)offersfurthersupportforthebenefitsof
touch-typing. Limited evidence relates specifically to
children; there was a trend for less musculoskeletal
discomfort in US children aged 12–13 years who could
touch-type (Jacobs and Baker 2002). It could not be
determined whether this protective effect was related to
the adoption of better posture or that children who
could touch-type finished the task more quickly.
However, either mechanism is likely to be beneficial.
Postural variability was found to be reduced in
adult touch-typists in a study by Straker et al. (2009c).
However, further analysis revealed that the less static
postures associated with non-touch-typists were actu-
ally still highly stereotypical, resulting from the
alternation of two head postures, which corresponded
to looking at the screen and viewing the keyboard.
This apparently greater variability, therefore, may not
prove to be an advantage, given the more flexed head
position that is associated with viewing the keyboard
and the benefits of touch-typing described above.
Szeto et al.(2005)reportedmoreerratickey-
striking forces in symptomatic office workers. There-
fore, children should be taught to use minimal force.
Children should also be taught keyboard shortcuts to
provide alternatives to mouse use and thus greater
variety.
Based on the available evidence, it is recommended
that children should be taught to touch-type with
minimal force, to use keyboard shortcuts and be skilled
in software use.
2.5. Teach children to respond to discomfort
The uptake of computer use by children is a relatively
recent phenomenon and longitudinal studies of the
tracking into adulthood of postures and loads caused
by computer use have therefore not been undertaken.
According to Woods et al. (2002), however, there are
indications that back, neck and shoulder pain in
adolescence and childhood are risk factors for the
development of MSDs in adulthood. Children are
starting to use computers at a very young age (Rideout
et al.2003,Strakeret al.2006d).Durationofcomputer
use can be extensive, particularly for children attending
schools with mandatory notebook computer programs
(Harris and Straker 2000, Sommerich et al. 2007). The
effects of this computer use at a time when children are
growing rapidly and developing spinal postures are
now starting to manifest themselves in the population,
with reports of musculoskeletal discomfort in children
being commonplace (Harris and Straker 2000, Jacobs
and Baker 2002, Williams 2002, Szeto 2003, Hakala
et al.2006,Strakeret al.2006d).Ofgreatconcernisthe
recent research that demonstrates that computer use by
adolescents is related to their habitual sitting posture
(Straker et al. 2006c).
The American Optometric Association (undated)
states that a number of characteristics make children
particularly susceptible to negative visual consequences
of computer use. With limited self-awareness, children
may fail to respond to discomfort because of their
absorption in the task. They may also ignore
symptoms that would be addressed by adults because
they think that everyone else sees the same way they
do. These childhood attributes are equally relevant to
musculoskeletal discomfort and workstation set-up.
More than a quarter of the students in the study of
Harris and Straker (2000) reported that they would
continue with the computer task if they were
experiencing discomfort, with another 18% saying that
they would ‘not think about it’.
Based on the available evidence, it is recommended
that children should be taught to be aware of
discomfort and be given strategies to prevent it. Adult
assistance and the seeking of health professional advice
are also recommended if symptoms persist, to avoid
development of a disabling disorder.
3. Summary
Computer use by children is extensive and there have
been widespread concerns about the possible impacts
of this on health. This paper has reviewed the
evidence regarding the physical aspects of child–
computer interaction and provided recommendations
for wise use of computers. Subsequent detailed
guidelines are required, which review the evidence
with regard to the cognitive and social aspects of this
interaction.
Implementation of these guidelines should be
trialled, with the efficacy assessed by randomised
and controlled trials. It is anticipated that
implementation within schools will be relatively easy to
achieve for many guidelines, with home
implementation relying more on individual family
knowledge and motivation.
Aspects of these guidelines could be taught to
children by the various adults responsible for their
welfare and with an interest in children using
computers wisely. Thus, parents and teachers,
ergonomists and health professionals, software and
hardware designers and suppliers all have a role in
ensuring that children are able to use computers wisely.
472 L. Straker et al.
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