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SA Journal of Physiotherapy 2014 Vol 70 No 2
INTRODUCTION
Physiotherapists are often consulted for
advice regarding computer worksta-
tions and the use of ergonomic ofce
chairs to improve posture and muscu-
loskeletal pain (Nakazawa et al. 2002).
Upper quadrant musculoskeletal symp-
toms in the working population who use
visual display units (VDU) are increas-
ing and may be as high as 74 cases per
100 persons (Lindegard et al. 2012).
Recommendations are usually sup-
ported by anecdotal evidence (Brewer
et al. 2006, Westgaard, Winkel 1997,
Wærsted, Hanvold & Veiersted 2010).
The International Ergonomic
Association denes ergonomics as “the
application of theoretical principles
and methods of design in order to opti-
mise human health and performance by
understanding the interaction between
human beings and other elements in
their system” (International Ergonomics
Association 2011). An ergonomic chair
is one which has been designed in order
to improve the performance of its user.
The designs aim to reduce the stress
on musculoskeletal structures and thus
assist with the management and pre-
vention of symptoms and disorders
which result from prolonged sitting
(Juul-Kristensen et al. 2006). Various
ergonomic chair features are suggested
to aid the user: adjustable height, adjust-
able back support, castors with a wide
base of support, curved seat pan, arm
rests (adjustable or xed), cushioning
and the comfort of the chair (European
Agency for Safety and Health at Work
2005). However, research to afrm these
features is inconclusive (Van Niekerk,
Louw & Hillier 2012).
Studies into the effectiveness of
ergonomic interventions for musculo-
skeletal symptoms evaluate combined
interventions and rarely research the
benet of the chair alone (Brewer et al.
2006, Kennedy et al. 2010). A review
by van Niekerk et al (2012) showed a
trend supporting the use of ergonomic
ofce chairs to reduce upper quadrant
muscle activity as well as a reduction in
the intensity of the symptoms, although
the chair was not the sole intervention
in some of the studies reviewed. Only
one study included ofce workers (Van
Niekerk, Louw & Hillier 2012). The
supposed effect of the chair on the sub-
ERGONOMIC CHAIR INTERVENTION:
EFFECT ON CHRONIC UPPER QUADRANT
DYSFUNCTION, DISABILITY AND
PRODUCTIVITY IN FEMALE COMPUTER
WORKERS
Corresponding author:
21 Cambier Road
Kreupelbosch,
Cape Town
7945
choeben@telkomsa.net
ABSTRACT
AIM: To compare the effect of two ergonomic chairs on upper quadrant musculoskeletal
pain and tension, disability and productivity among female computer workers in the
ofce workplace.
METHODS: A series of two N=1 studies were conducted using the A-B-A-C-A design
whereby an intervention ergonomic chair was compared to a less adjustable control
ergonomic chair using visual analogue scales (VAS) for pain and muscle spasm, the
Neck Disability Index and the Work Productivity and Activity Impairment questionnaire.
The female participants were assessed over the four week phases as they performed
high intensity visual display unit work. The results were compiled and tabulated.
RESULTS: Both the control and intervention ergonomic chairs showed a reduction in both the mean and variance of pain and
muscle spasm. The second participant also showed an increase in productivity with both chairs.
CONCLUSION: The introduction of an ergonomic chair shows a reduction in VAS intensity and frequency for pain and muscle
spasm, as well as a reduction in variance of the symptoms. Both chairs showed a similar reduction in symptoms, thus indicating
almost equivalent benet from the use of both ergonomic chairs.
KEYWORDS: ERGONOMIC CHAIR, UPPER QUADRANT PAIN AND SPASM, DISABILITY, PRODUCTIVITY,
OFFICE WORKERS
Hoeben C, (MSc)1
Louw Q, (PhD)1
1University of Stellenbosch
Research
Article
12 SA Journal of Physiotherapy 2014 Vol 70 No 2
time employees working on a computer
for ve to eight hours per day, Monday to
Friday. The subjects had a minimum two
year history of similar employment and a
history of neck and/or shoulder pain for a
minimum of three months. The subjects
attributed their pain to sitting or their work
environment.
Subjects were to be excluded if there was
a presence of neurological signs or symp-
toms in the upper and lower quadrants, or if
they had previous spinal surgery or trauma,
malignancy or pathology which may con-
tribute to their pain and perceived disability
of their upper quadrant. Current or planned
pregnancy was an exclusion criterion as
there is an inuence on body anthropome-
try (Yu, Wong 1996) as well as inuencing
the ability to be eligible for the study dura-
tion. The presence of forearm, wrist and
hand symptoms deemed the subject ineli-
gible as this is a result of typing as opposed
to sitting (Slot et al. 2009). Being classied
as having a high risk of yellow ags as
calculated on the Örebro Musculoskeletal
Pain Questionnaire (OMPQ) was an exclu-
sion criterion. A total of 105 or more for
the OMPQ indicates an increased risk of
psychosocial factors inuencing disability,
perceived pain and outcomes (Hagberg,
Tornqvist & Toomingas 2002). Body mass
over 100kg excluded the subject as this is
the maximum weight capacity for the inter-
vention ergonomic chair.
Subjects were recruited from legal
rms, university administration divisions
and accountant and brokering companies
via emails to the human resources depart-
ments. An email inviting possible par-
ticipants was sent by the Human Resource
departments to employees.
Eligible subjects were screened by
the principal researcher by performing a
subjective and objective evaluation. The
physical examination was conducted
Study design
A single subject, N=1, randomised, A-B-
A-C-A design study was conducted with
two participants. N=1 studies require
the symptoms to be long standing and
stable. Each of the ve phases lasted
four weeks. It was hypothesised that the
more adjustable intervention ergonomic
chair (see table 1) would have a greater
effect on reducing pain, muscle spasm,
disability and productivity, compared to
the control ergonomic chair with fewer
adjustable features.
During Phase A1 (initial baseline) the
subject used her usual ofce chair.
During Phase B (the rst intervention
phase), the subject either used the inter-
vention or control ergonomic chair. The
randomisation of the chair for Phase B
was done using an online random number
generator by one of the researchers (R1).
The random allocation sequence was
placed in numbered opaque envelopes
and given to another researcher (R2) who
was contacted by the researcher (R3) after
the subject was enrolled into the study to
reveal which chair should be allocated
during Phase B. Participants remained
masked to the intervention as both the
intervention and control chairs were new
and similar in design.
Phase A2 was the rst washout phase
and the subject used her usual chair,
followed by Phase C, when either the
control or intervention chair was admin-
istered, depending on which chair was
provided in Phase B.
Phase A3 was the second wash-out
phase with the subject using her usual
ofce chair.
Subject description and
recruitment
Female ofce workers aged between 25
and 50 years were recruited. They were full
ject’s symptoms may be due to the effect
of the known contributors to the devel-
opment of upper quadrant work-related
musculoskeletal disorders (UQWMSD).
These physical stressors are:
• Prolonged sitting or static postures
(Grifths, Mackey & Adamson
2007) {{51 Grifths, K.L. 2007;
403 Nakazawa,Tetsuya 2002}};
• The duration of computer usage
(Nakazawa et al. 2002);
• The position of the body in rela-
tion to the work space (Nakazawa
et al. 2002, Grifths, Mackey &
Adamson 2007)
• Keyboard height in relation to
the user where the keyboard is
higher than the height of the
elbow or elbow exion is greater
than 121° (Marcus et al. 2002)
• Forward head-on-neck posture
where the head is 20% more
exed than neutral (Prins 2008)
Sitting discomfort and incorrect chair
height have also been shown to inuence
musculoskeletal symptoms (Lindegard
et al. 2012, Yu, Wong 1996). Gender is
another risk factor for UQWMSD with
women at greater risk (Hoy et al. 2010) and
being more likely to develop recurrent or
chronic symptoms (Janwantanakul et al.
2008). These factors, including the cost of
the chair, are considered when a new chair
is considered by ofce workers.
The aim of this study was therefore
to assess the effect of a fully adjustable
ergonomic intervention chair against a
less adjustable, cheaper ergonomic control
chair in women with upper quadrant symp-
toms and who perform high load VDU
work. The hypothesis was that the more
adjustable and more expensive chair would
have a greater impact on upper quadrant
musculoskeletal symptoms than the less
adjustable and less expensive chair, but that
both chairs would show an improvement in
the selected outcomes.
Two chairs were compared to the sub-
ject’s own ofce chair; the intervention
ergonomic chair with adjustable back sup-
port, height and arm support, and the con-
trol ergonomic chair with only adjustable
height and back support and which was a
third of the cost of the intervention chair.
METHODOLOGY
Ethics approval was obtained from the
Health Research Ethics Committee at the
University of Stellenbosch (N11/11/325)
and each participant provided signed
informed consent.
Features of ergonomic chairs Intervention chair Control chair
Padded √ √
Mid-back √ √
Five star castor base √ √
Height adjustable √ √
Angled and contoured lumbar support √ √
Height adjustable armrests √ X
Moulded waterfall edge seat √ √
Adjustable inclination of backrest √ √
Adjustable resistance of the backrest √ X
Cost 2.5x x
Table 1: Features of the intervention and control ergonomic chairs as
used in the study.
13
SA Journal of Physiotherapy 2014 Vol 70 No 2
administered twice a week on a Tuesday
and Friday afternoon between 2p.m. and
3p.m. The NDI and WPAI were adminis-
tered once a week on a Friday afternoon
together with the VAS outcomes.
All outcomes were administered elec-
tronically and returned to the researchers
via email. The outcomes were printed
and the results entered manually and
compiled onto a Microsoft Excel 2010
spread sheet. Unfortunately, due to limi-
tations, the researcher was not blinded as
to which chair the participant received.
End of phase and exit
questionnaires
An end of phase email, with specic
questions regarding symptoms, medica-
tion usage and chair usage and changes
during the four week phase, was sent
on the last day of each phase. An exit
email questionnaire was sent at the end
of the entire study. The questions asked
the participant whether there had been
any stressful event during the study, if
there had been any injuries sustained
and whether the participant had changed
medication throughout the 20 weeks.
Subjects were requested to give any rel-
evant information, such as a change in
exercise routine, which may have inu-
enced the results.
Data analysis
All data was captured on a Microsoft
Excel 2010 spread sheet and the mean
calculated for each phase of each out-
come. The range was calculated as a
measure of variance for each outcome.
For the primary outcomes of all four
VAS scales, line graphs were con-
structed to illustrate the mean, with error
bars indicating the range.
RESULTS
Participant description:
Table 2 shows the main ndings for the
two participants. Both participants do
high volume VDU work and have neck,
shoulder and upper thoracic symptoms
attributed to their work environment.
Examination revealed that both partici-
pants had poor cervical motion control
(tested with cranio-cervical exion test
(Falla, Jull & Hodges 2004)) as well as
increased palpable muscle tone in the
upper trapezius, scalene and levator
scapulae muscles. Participant 1’s chair
had xed arm rests and a xed back rest
and participant 2’s chair had no armrests.
There was no history of upper quadrant
at the same height as the keyboard; the
back rest position was set up between
100° and 110°, and the participant’s feet
had to touch the oor or be on a foot rest.
This is in accordance with the guidelines
set out by the European Agency for
Safety and Health at Work (European
Agency for Safety and Health at Work
2005). Identical information regarding
the features of the intervention and con-
trol chairs was given to each participant
according to the training received by
the researchers. The participants were
shown how to adjust the back support
from a xed to a mobile position and
the height of the chair to allow for the
correct arm height. For the interven-
tion chair, the participants also received
instruction on how to adjust the arm
rests according to elbow height or chair
position. No ergonomic training regard-
ing posture; workstation setup; or work
changes was given.
Selected outcome measures
The primary outcome measures were
Visual Analogue Scales (VAS). There
were a total of four VAS scores: mus-
cle tension intensity; muscle tension
frequency; pain intensity; and pain fre-
quency.
For VAS outcomes, reliability
and validity have been established
(Gajasinghe, Wijayaratna & Abayadeera
2010, Hawker et al. 2011). The minimal
clinically important difference (MCID)
has been shown for chronic conditions,
such as rheumatoid arthritis and rotator
cuff disease to be between 11 and 13.7
points out of one hundred. (Hawker et
al. 2011)
The two secondary outcome measures
were the Neck Disability Index (NDI)
as a measure of disability and the Work
Productivity and Activity Impairment
health questionnaire (WPAI) as a meas-
ure of productivity.
For NDI, validity and reliability
for chronic neck pain has been estab-
lished (Gay, Madson & Cieslak 2007,
Pietrobon et al. 2002). The MCID has
been shown to be seven points out of 50
(Cleland et al. 2006).
The WPAI has been shown to have
both construct validity and reliability
(Reilly et al. 2010). MCID has not been
established for neck pain.
Measurement time frames and
method of outcomes
For all phases, the four VAS scores were
according to Neuromusculoskeletal
Examination and Assessment (Petty
2011) at their place of work.
A work station assessment was con-
ducted according to the European Agency
for Health and Safety at Work (European
Agency for Safety and Health at Work
2005). A workstation that did not comply
with these standards made the candidate
ineligible for the study. This eliminated
other work station and ergonomic factors
which may inuence the upper quadrant
symptoms. These factors were:
• lighting and noise interference;
• mouse and keyboard position and
adjustability;
• desk height and position;
• computer position; and
• screen adjustability.
Factors which are not within the
accepted ranges have been shown to
adversely inuence UQWMSD and thus
may interfere with the results of this study.
The only workstation intervention by the
researcher was to provide a foot rest to
the participants for the full duration of the
study if it was deemed necessary for cor-
rect chair set up (Helander, Rupp 1984).
This ensured correct elbow height and
maintained foot contact with a solid sur-
face as per the guidelines of the European
Agency for Safety and Health at Work
(European Agency for Safety and Health at
Work 2005). No other changes to the par-
ticipants’ workstations or chairs were made.
Informed signed consent was obtained
from each eligible participant in the study
by the researcher after they agreed to par-
ticipate in the study.
Description of the intervention
and control chairs
The similarities and differences between
the chairs are illustrated in Table 1.
Figure 1 shows photographs of the
participants’ own chairs. For the study,
all labelling was removed from the ergo-
nomic chairs to ensure blinding of the
participant as to which chair was the con-
trol and intervention ergonomic chair.
Ergonomic chair intervention
For Phase B and Phase C, the ergonomic
chairs were to be set up by the researcher
according to training received by the
intervention ergonomic chair manufac-
turer. The chair height was set up such
that the participant’s elbows were in line
with the desk; the arm rest height such
that the elbows were supported on the
rests whilst sitting in the chair and were
14 SA Journal of Physiotherapy 2014 Vol 70 No 2
1.25/50 and 0.5/50 in the intervention
phases.
Work Productivity and Activity
Impairment health questionnaire
(WPAI):
For participant 1, all WPAI values were
0, and thus no data analysis could be per-
formed.
Participant 2 showed a reduction
in the percentage that the symptoms
affected her productivity from 40% in
the baseline phase to 7.5% in Phase B
and 5% in phase C.
End of phase and exit emails:
Table 4 and table 5 represent the data
from the end of phase and exit emails.
Participant 1 stopped using the control
chair in the nal 2 days of Phase C due
to lower back pain which she attributed
to the chair. This also resulted in visits to
her general practitioner and physiothera-
pist for treatment and medication for the
resultant lower back pain.
Participant 1 noted that her only
change during the study was to start
pilates in the nal phase of the study.
Participant 2 noted an increase in
general stress levels due to personal cir-
cumstances as well as an increase in work
load. She also started pilates and running
during the baseline phase of the study.
The trend of the data for
participant 1 shows only a
slight reduction in the mean
for all VAS outcomes. The
change to the mean scores
over the course of the study is
below 5/100 for all outcomes.
The reduction in the
mean from the baseline to
subsequent phases is signi-
cantly greater for participant
2. However, similar to par-
ticipant 1, the means for the
subsequent phases remains
lower than phase 1.
Both participants’ results
show a similar trend towards
a reduction in variance or
range of symptoms with both the control
and intervention chairs as shown by the
values in Table 3 and graphs in Figure 2
and gure 3.
Standard deviation (SD) was calcu-
lated for four VAS, however, as the vari-
ance was so large, that the -2SD value
was in the negative which is not plau-
sible for a VAS as its lowest value is 0.
Neck Disability Index (NDI):
As shown in Table 3, the NDI values for
participant 1 were very low. The val-
ues for participant 2 were higher in the
baseline phase and reduced to between
injury or disease for either participant.
Both participant 1 and participant 2 had
lower than expected initial VAS scores. In
the subjective assessments at the begin-
ning of the interview process, participant 1
rated her pain according to the numeric pain
scale (NPS) at a minimum of 5/10, how-
ever her initial VAS showed only a 10/100
pain intensity, not the expected 50/100.
Participant 2’s NPS at assessment was 6/10
however her initial pain intensity VAS was
16/100 and not the expected 60/100.
Visual analogue scales (VAS):
Table 3 shows the means and ranges for
all phases for all outcomes.
Partici-
pant
Age
(yrs)
Current
work
(years)
VDU
hours/day
Symptom
duration Area of pain Aggravating
factors
Easing
factors
Physical
examination
findings
Work
station
findings
OMPQ
(<105) and
red flags
1 50 Stock
broker
(4yrs 9m)
9hrs 10 yrs A1- Neck and
headache
Constant
5/10 to 8/10
A2- Upper thoracic
and shoulders
Intermittent
7/10
A1- neck
movements
A2- long
duration sitting
A1 and A2 –
stress at work
and increased
work load
Heat
Traumeel©
Physio-
therapy
Movement
and light
exercise
Forward Head
Posture and Tx
kyphosis
Cx side flexion
ROM
Motor control
Cx flexion
tone UT, scalenes
& LS
No footrest
Arm
rests not
adjustable
OMPQ score
64 (low risk)
No red flags
2 29 Data
capturer
(3yrs 3m)
7-8hrs 2yrs 6m A1- bilat upper
trapezius area and
posterior neck
Intermittent
8/10
A2- Upper thoracic
and between
scapulae
Intermittent
6/10
A1- increased
work load
A1 and A2- long
duration sitting,
increased stress
at work
Massage
NSAID’s and
pain
medication
A2- eased
with
movement
Forward Head
Posture and Tx
kyphosis
Ipsilateral A1 at end
of Cx
rotation
motor control
Cx extension
tone UT,
scalenes & LS
No armrests OMPQ score
98 (low risk)
Dizziness
caused by
low blood
sugar
Cx – cervical spine; Tx- thoracic spine; UT-upper trapezius; LS-levator scapulae; OMPQ- Orebro Musculoskeletal Pain Questionnaire
Table 2: Participant description
Above left: Figure 1a. Above right: Figure 1b
Figure 1: Photographs of chairs used in the study; 1a-Participant
1’s own chair; 1b-Participant 2’s own chair.
15
SA Journal of Physiotherapy 2014 Vol 70 No 2
cles (Marcus et al. 2002). The corrected
elbow angle, and head-on-neck position
discourages extreme postural angles
which are associated with sitting-related
pain (Prins 2008).
In this study, the participants did not
receive any education regarding postural
alignment or sitting behaviour. The par-
ticipants were informed of the features of
the chairs and as such could adjust them
according to their own comfort and dis-
cretion (Amick III et al. 2003, Robertson
et al. 2009). As neck and upper quadrant
sitting positions vary in symptomatic as
well as asymptomatic subjects (Szeto,
Straker & Raine 2002, Szeto, Straker
& O'Sullivan 2005), it may be that it
is important for physiotherapists to
empower clients on how to adjust their
own chairs rather than implementing
strategies which are aimed at teaching
uniform posture. Prolonged static pos-
tures have been shown as a contributing
factor to the development of UQWMSD
reported pain and muscle spasm. This
research is consistent with the results
of Amick et al (2003) and Robertson et
al (2009). However their interventions
included specic posture and ofce
setup ergonomic training together with
the ergonomic chair.
The underlying mechanism of this
positive change in symptoms remains
debatable. One probable explanation is
that there was a change in relative pos-
tural alignment of the neck, thoracic
spine and upper limbs. In this study, we
specically ensured that the elbows were
positioned in such a manner that they
were supported on the arm rests at the
same height as the keyboard. The use of
a footrest ensured that the height of the
chair could be correct according to the
desk height while the participant’s feet
remained supported. Previous research
has indicated that adjusting the elbow
position in this manner reduces strain
on the upper quadrant joints and mus-
DISCUSSION
Ergonomic adaptations are a common
workplace intervention to reduce upper
quadrant musculoskeletal symptoms
(Anderson 2006). This is the rst study
to report whether an ergonomic ofce
chair, irrespective of arm rest adjustabil-
ity, could have an effect on pain, muscle
tension, productivity and disability. The
ndings of this single subject design
study illustrated an immediate reduc-
tion in the intensity and variance of the
symptoms following the introduction
of the ergonomic chair, irrespective of
which chair was allocated for the rst
intervention phase. Two strengths of
this study were the random allocation of
the chairs and that the participants were
unaware of the cost of each chair as well
as which of the chairs was the control or
intervention. This contributes towards
the validity of the study outcomes.
The ndings illustrated a reduction
in both frequency and intensity of self-
Study phase A1 B A2 C A3
Outcome measure Range (mm)
Mean (SD)
Range (mm)
Mean (SD)
Range (mm)
Mean (SD)
Range (mm)
Mean (SD)
Range (mm)
Mean (SD)
Pain: Frequency (VAFS) (/100)
Participant 1
Participant 2
18 (5-23)
12.125 (5.06)
49 (19-68)
42.5 (21.39)
9 (6-15)
9.333 (3.14)
12 (3-15)
5.75 (4.89)
3 (7-10)
9 (1.29)
2 (3-5)
3.5 (0.93)
6 (5-11)
8.857 (2.04)
7 (0-7)
1.625 (2.56)
4 (6-10)
9 (1.60)
4 (0-4)
0.88 (1.64)
Pain: Intensity (VAIS) (/100)
Participant 1
Participant 2
21 (7-28)
11.63 (7.95)
51 (16-67)
36 (18.99)
15 (6-21)
9.33 (6.06)
7 (3-10)
4.75 (3.54)
5 (6-11)
8.26 (1.70)
2 (3-5)
3.25 (0.71)
5 (5-10)
7.17 (2.23)
9 (0-9)
1.88 (3.18)
7 (4-11)
7.13 (2.1)
7 (0-7)
1.5 (2.83)
Muscle tension: Frequency
(VAFS) (/100)
Participant 1
Participant 2
23 (10-33)
14.13 (8.24)
52 (18-70)
45.25 (19.69)
10 (9-19)
11.33 (3.83)
25 (0-25)
7.5 (8.21)
7 (8-15)
10.29 (2.29)
7 (3-10)
4.38 (2.45)
4 (8-11)
9.71 (1.11)
8 (0-8)
1.75 (2.87)
8 (7-15)
10.38 (2.33)
11 (0-11)
3.38 (4.78)
Muscle Tension: Intensity
(VAIS) (/100)
Participant 1
Participant 2
25 (8-33)
12.13 (8.74)
50 (19-58)
38.88 (18.28)
9 (6-15)
9.67 (4.03)
19 (0-19)
5.25 (6.25)
6 (7-13)
9 (2.45)
5 (0-5)
3.13 (1.55)
4 (4-10)
7.71 (1.8)
9 (0-9)
1.88 (3.18)
4 (7-11)
8.38 (1.51)
9 (0-9)
2.29 (4.02)
NDI (/50)
Participant 1
Participant 2
2 (1-3)
2 (0.82)
11 (8-19)
12.5 (5.45)
1 (2-3)
2.67 (0.56)
2 (0-2)
1.250 (0.98)
1 (2-3)
2.67 (0.56)
4 (0-4)
2 (1.83
0 (3)
3 (0)
2 (0-2)
0.5 (1)
0 (3)
3 (0)
2 (0-2)
1 (0.82
WPAI
Participant 1
Participant 2
(expressed as a percentage)
0
40 (20-60)
40 (18.257)
0
20 (0-20)
7.5 (9.574)
0
10 (0-10)
2.5 (5)
0
10 (0-10)
5 (5.773)
0
0
0
Table 3: Study results per phase for both participants
16 SA Journal of Physiotherapy 2014 Vol 70 No 2
the majority of the participants (Dainoff,
Cohen & Dainoff 2005).
As the footstool was introduced for
Participant 1 from the start of the study, it
may be the cause of the low scoring of the
VAS from the beginning of the baseline
phase A1. In the subjective assessment,
Participant 1 claimed that her pain was
5/10. However, her baseline mean was
lower from the start. As the change in
the chair was shown to be almost imme-
diate, it is possible that the introduction
of the footstool improved Participant 1’s
outcomes immediately too. The footstool
would have altered Participant 1’s sitting
rst intervention phase. This change is
irrespective of which ergonomic chair the
participants were given. A similar effect
on the pain cycle is suggested by Clark et
al (2012) as a response to manual therapy
where by the pain-spasm-pain cycle is
disrupted by a physiotherapy interven-
tion (Clark et al. 2012). This may explain
the maintenance of symptom reduction
throughout the washout phases of this
study. Similar results of prolonged effect
of an ergonomic intervention were shown
in an International study by Dainoff et
al. 2005 where the improvements were
still present at one year follow up for
(Grifths, Mackey & Adamson 2007),
educating a client to adjust their sitting
position occasionally may reduce this
risk. This may also explain why the
symptoms were not exacerbated dur-
ing the washout and nal phases of this
study since participants indicated that
they adjusted their own ofce chairs.
The changes to the mean and variance
of the outcomes in the rst intervention
phase are maintained throughout the
rest of the study phases, including the
washout A2 and nal A3 phases. There
appears to be a break in the chronic pain
and muscle spasm cycle following the
Phases Medication (pain/spasm) Healthcare
consultation % time in chair Chair adjustments
A1 No Yes – osteopath for leg
injury 100% Yes – raised
B – Intervention chair No Yes – osteopath for leg
injury 100% Yes – lowered
A2 No No 100% No
C – Control chair Yes - Celebrex Yes – GP and physio
for LBP
90% - stopped due to
LBP
No – but stopped
using chair
A3 Yes- Celebrex Yes – GP and physio
for continued LBP 100% No
Table 5: Results of end of phase emails for Participant 2
Phases Medication (pain/
spasm)
Healthcare
consultation
% working time in
chair Chair adjustments
A1 No No 90% No
B – Control chair No No 90% No
A2 No No 70% No
C – Intervention chair Yes – menstrual pain No 80% No
A3 Yes – menstrual pain No 80% No
Table 4: Results of the end of phase emails for Participant 1
Figure 2: Graphs depicting mean values for VAS outcomes for Participant 1 showing variability of data for
each phase
17
SA Journal of Physiotherapy 2014 Vol 70 No 2
not return during the washout phase, it is
less likely that the subconscious effect of
using a new chair was the main cause of
the change in outcomes. This study only
researched the effect of the chair on upper
quadrant symptoms and research into the
effect of pain in other areas is warranted.
Future studies into prevention of
work-related musculoskeletal dysfunc-
tion should also be conducted.
CONCLUSION
The aim of this study was to ascertain
the effect of a fully adjustable computer
workstation chair compared to a chair
with limited adjustability (armrests
not adjustable) on sitting-related upper
quadrant pain, muscle spasm, disability
in female ofce workers. The ndings of
this series of single subject (N=2) study
illustrated that both intervention chairs
reduced the intensity, frequency and
variability of pain and muscle spasm.
This implies that ofce chairs without
adjustable armrests may be equivalent to
more expensive fully adjustable chairs
with respect to pain, muscle spasm and
disability. Further research with larger
population studies and longer follow–up
time frames is now required to afrm
these ndings in a representative sample.
ACKNOWLEDGEMENTS
The South African Society of Physio-
therapy is thanked for support and fund-
ing for the purchase of the equipment
required for the study.
tions. However it acknowledged that the
research is of only moderate strength.
Brewer et al also noted that, although
ergonomic chairs have been shown with
moderate evidence to be benecial, the
feature of arm rest adjustability has not
been shown to be denitively bene-
cial (Brewer et al. 2006). The improve-
ment in the disability shows the benet
at an individual level for the client or
employee to invest in their own ofce
equipment. The ndings illustrated that
the added benet of adjustable arm rests
may be small. However caution must
be applied as this study did not aim to
assess durability or long term effects to
estimate cost effectiveness.
Limitations and
recommendations:
This study had only two participants
and larger studies are needed before the
results can be generalised. The wash-
out phase may need to be lengthened to
the point where the subject’s outcomes
return to that of the baseline phase. This
will make the comparison of the inter-
vention phases more obvious.
Blinding of the researcher as to which
chair was provided during the interven-
tion phases would have added to the
quality of the study.
The Hawthorne effect (Adair 1984),
which is the alteration of behaviour by
the subjects of a study because they are
being observed, may have had an effect in
this study. However, as the symptoms did
position and thus her upper quadrant pos-
ture and muscle activity. Further research
into the effect of providing only a foot-
stool is required to analyse this effect.
Participant 2 showed a reduction in both
mean and variability following the rst
intervention phase. These results may have
been more prominent when compared to
participant 1’s results as participant 2’s
own/original chair was more basic. It
lacked arm rests and had a lower back rest
compared to the ergonomic chairs pro-
vided for the study and when compared
to participant 1’s own chair (gure 1a and
gure 1b). Participant 1’s chair was similar
to the intervention chairs, but lacked full
adjustability. The effect of arm rests on
pain and symptoms has been shown in the
review by Kennedy et al (2010) to have a
positive inuence on upper quadrant pain
and symptoms. However, not all stud-
ies on the subject concur as some studies
show no effect (Brewer et al. 2006).
Economic cost of an ergonomic chair
is an important consideration when plan-
ning a computer work station interven-
tion. This research illustrates that the
lower cost chair may be adequate to
improve musculoskeletal symptoms in
the short term. The change in produc-
tivity shown by participant 2 may help
encourage employees and companies
to invest in improved ergonomic ofce
equipment with the minimal require-
ments of lumbar and height adjustabil-
ity as well as footrests. The review by
Tompa et al (2010) had similar sugges-
Figure 3: Graph depicting mean values for VAS outcomes for Participant 2 showing variability of data for each phase
18 SA Journal of Physiotherapy 2014 Vol 70 No 2
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