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Ergonomic chair intervention: Effect on chronic upper quadrant dysfunction, disability and productivity in female computer workers


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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 office 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 benefit from the use of both ergonomic chairs.
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SA Journal of Physiotherapy 2014 Vol 70 No 2
Physiotherapists are often consulted for
advice regarding computer worksta-
tions and the use of ergonomic ofce
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 denes 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 afrm 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
benet 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
ofce 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 ofce workers (Van
Niekerk, Louw & Hillier 2012). The
supposed effect of the chair on the sub-
Corresponding author:
21 Cambier Road
Cape Town
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
ofce 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 benet from the use of both ergonomic chairs.
Hoeben C, (MSc)1
Louw Q, (PhD)1
1University of Stellenbosch
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
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 inuence on body anthropome-
try (Yu, Wong 1996) as well as inuencing
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 classied
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 inuencing 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 ofce 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
ofce chair.
Subject description and
Female ofce 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
(Grifths, Mackey & Adamson
2007) {{51 Grifths, 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, Grifths, 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 inuence
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 ofce 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 ofce 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.
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.
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
An end of phase email, with specic
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 inu-
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.
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-
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 inuence the upper quadrant
symptoms. These factors were:
lighting and noise interference;
mouse and keyboard position and
desk height and position;
computer position; and
screen adjustability.
Factors which are not within the
accepted ranges have been shown to
adversely inuence 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
Work Productivity and Activity
Impairment health questionnaire
For participant 1, all WPAI values were
0, and thus no data analysis could be per-
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.
duration Area of pain Aggravating
(<105) and
red flags
1 50 Stock
(4yrs 9m)
9hrs 10 yrs A1- Neck and
5/10 to 8/10
A2- Upper thoracic
and shoulders
A1- neck
A2- long
duration sitting
A1 and A2 –
stress at work
and increased
work load
and light
Forward Head
Posture and Tx
Cx side flexion
Motor control
Cx flexion
tone UT, scalenes
& LS
No footrest
rests not
OMPQ score
64 (low risk)
No red flags
2 29 Data
(3yrs 3m)
7-8hrs 2yrs 6m A1- bilat upper
trapezius area and
posterior neck
A2- Upper thoracic
and between
A1- increased
work load
A1 and A2- long
duration sitting,
increased stress
at work
NSAID’s and
A2- eased
Forward Head
Posture and Tx
Ipsilateral A1 at end
of Cx
motor control
Cx extension
tone UT,
scalenes & LS
No armrests OMPQ score
98 (low risk)
caused by
low blood
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.
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 specic posture and ofce
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
specically 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-
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 ofce
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
Participant 1
Participant 2
(expressed as a percentage)
40 (20-60)
40 (18.257)
20 (0-20)
7.5 (9.574)
10 (0-10)
2.5 (5)
10 (0-10)
5 (5.773)
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
(Grifths, 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 ofce 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
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/
% 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
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.
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 ofce 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 ofce 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 afrm
these ndings in a representative sample.
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 benecial, the
feature of arm rest adjustability has not
been shown to be denitively bene-
cial (Brewer et al. 2006). The improve-
ment in the disability shows the benet
at an individual level for the client or
employee to invest in their own ofce
equipment. The ndings illustrated that
the added benet 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
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 inuence 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 ofce
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
Nakazawa, T., Okubo, Y., Suwazono, Y., Kobayashi,
E., Komine, S., Kato, N. & Nogawa, K. 2002,
"Association between duration of daily VDT use
and subjective symptoms", American Journal of
Industrial Medicine, vol. 42, no. 5, pp. 421-426.
Petty, N. (ed) 2011, Neuromuscular Examination
and Assessment; A handbook for therapists,
Churchill Livingstone Elsevier, London.
Pietrobon, R., Coeytaux, R.R., Carey, T.S.,
Richardson, W.J. & DeVellis, R.F. 2002, "Standard
Scales for Measurement of Functional Outcome
for Cervical Pain or Dysfunction: A Systematic
Review.", Spine, vol. 27, no. 5, pp. 515-522.
Prins, Y. 2008, The aetiology of upper quadrant
musculoskeletal pain in high school learners using
desktop computers : a prospective study, University
of Stellenbosch.
Reilly, M.C., Gooch, K.L., Wong, R.L., Kupper,
H. & van der Heijde, D. 2010, "Validity, reliability
and responsiveness of the Work Productivity and
Activity Impairment Questionnaire in ankylosing
spondylitis", Rheumatology (Oxford, England), vol.
49, no. 4, pp. 812-819.
Robertson, M., Amick III, B.C., DeRango, K.,
Rooney, T., Bazzani, L., Harrist, R. & Moore, A.
2009, "The effects of an ofce ergonomics training
and chair intervention on worker knowledge,
behavior and musculoskeletal risk", Applied
Ergonomics, vol. 40, pp. 124-135.
Slot, T., Charpentier, K., Dumas, G., Delisle,
A., Leger, A. & Plamondon, A. 2009,
"Evaluation of forearm support provided by
the Workplace Board on perceived tension,
comfort and productivity in pregnant and non-
pregnant computer users", work, vol. 34, pp. 67-77.
Szeto, G.P.Y., Straker, L.M. & O'Sullivan, P.B. 2005,
"A comparison of symptomatic and asymptomatic
ofce workers performing monotonous keyboard
work - 2: Neck and shoulder kinematics", Manual
therapy, vol. 10, no. 4, pp. 281-291.
Szeto, G.P.Y., Straker, L. & Raine, S. 2002, "A
eld comparison of neck and shoulder postures in
symptomatic and asymptomatic ofce workers",
Applied Ergonomics, vol. 33, no. 1, pp. 75-84.
Van Niekerk, S.-., Louw, Q.A. & Hillier, S. 2012,
"The effectiveness of a chair intervention in the
workplace to reduce musculoskeletal symptoms.
A systematic review", BMC Musculoskeletal
Disorders, vol. 13.
Wærsted, M., Hanvold, T.N. & Veiersted, K.B. 2010,
"Computer work and musculoskeletal disorders of
the neck and upper extremity: A systematic review",
BMC Musculoskeletal Disorders, vol. 11, pp. 79-94.
Westgaard, R. & Winkel, J. 1997, "Ergonomic
intervention research for improved musculoskeletal
health: a critical review", International Journal of
Industrial Ergonomics, vol. 20, no. 6, pp. 463-500.
Yu, I.T.S. & Wong, T.W. 1996, "Musculoskeletal
problems among VDU workers in a Hong Kong
bank", Occupational Medicine, vol. 46, no. 4, pp.
Musculoskeletal Symptoms: A Literature Review",
Journal of Occupaltional Rehabilitation, vol. 17,
pp. 743-765.
Hagberg, M., Tornqvist, E.W. & Toomingas,
A. 2002, "Self-Reported Reduced Productivity
due to Musculoskeletal Symptoms: Associations
WithWorkplace and Individual Factors Among
White-Collar Computer Users", Journal of
Occupational Rehabilitation, vol. 12, no. 3, pp.
Hawker, G.A., Mian, S., Kendzerska, T. & French,
M. 2011, "Measures of adult pain: Visual Analog
Scale for Pain (VAS Pain), Numeric Rating Scale
for Pain (NRS Pain), McGill Pain Questionnaire
(MPQ), Short-Form McGill Pain Questionnaire
(SF-MPQ), Chronic Pain Grade Scale (CPGS),
Short Form-36 Bodily Pain Scale (SF-36 BPS),
andMeasure of Intermittent and Constant
Osteoarthritis Pain (ICOAP)", Arthritis Care and
Research, vol. 63, pp. S240-S252.
Helander, M.G. & Rupp, B.A. 1984, "An overview
of standards and guidelines for visual display
terminals", Applied Ergonomics, vol. 15, no. 3, pp.
Hoy, D.G., Protani, M., De, R. & Buchbinder, R.
2010, "The epidemiology of neck pain", Best
practice & research. Clinical Rheumatology, vol.
24, no. 6, pp. 783-792.
International Ergonomics Association 2011,
2011/11/28-last update, The Denition of
Ergonomics [Homepage of International
Ergonomics Association], [Online]. Available:
Ergonomics.html [2013, June 28].
Janwantanakul, P., Pensri, P., Jiamjarasrangsri, V. &
Sinsongsook, T. 2008, "Prevalence of self-reported
musculoskeletal symptoms among ofce workers",
Occupational Medicine, vol. 58, pp. 436-438.
Juul-Kristensen, B., Kadefors, R., Hansen, K.,
Bystro¨m, B., Sandsjo¨, L. & Sjøgaard, G. 2006,
"Clinical signs and physical function in neck and
upper extremities among elderly female computer
users: the NEW study", European Journal of
Applied Physiology, vol. 96, pp. 136-145.
Kennedy, C.A., Amick, B.C.,3rd, Dennerlein,
J.T., Brewer, S., Catli, S., Williams, R., Serra, C.,
Gerr, F., Irvin, E., Mahood, Q., Franzblau, A.,
Van Eerd, D., Evanoff, B. & Rempel, D. 2010,
"Systematic review of the role of occupational
health and safety interventions in the prevention of
upper extremity musculoskeletal symptoms, signs,
disorders, injuries, claims and lost time", Journal
of Occupational Rehabilitation, vol. 20, no. 2, pp.
Lindegard, A., Wahlstrom, J., Hagberg, M.,
Vilhelmsson, R., Toomingas, A. & Tornqvist, E.W.
2012, "Perceived exertion, comfort and working
technique in professional computer users and
associations with the incidence of neck and upper
extremity symptoms", BMC musculoskeletal
disorders, vol. 13, pp. 38.
Marcus, M., Gerr, F., Monteilh, C., Ortiz, D.J., Gentry,
E., Cohen, S., Edwards, A., Ensor, C. & Kleinbaum,
D. 2002, "A prospective study of computer users: II.
Postural risk factors for musculoskeletal symptoms
and disorders", American Journal of Industrial
Medicine, vol. 41, no. 4, pp. 236-249.
Adair, J.G. 1984, "The Hawthorne effect: A
reconsideration of the methodological artifact",
Journal of Applied Psychology, vol. 69, no. 2, pp.
Amick III, B.C., Robertson, M.M., DeRango, K.,
Bazzani, L., Moore, A., Rooney, T. & Harrist, R.
2003, "Effect of ofce ergonomics intervention on
reducing musculoskeletal symptoms", Spine, vol.
28, no. 24, pp. 2706.
Anderson, J.H. 2006, "Intervention trials on
upper body pain among computer operators",
Occupational and environmental medicine, vol. 63,
pp. 297-298.
Brewer, S., van Eerd, D., Amick III, B.C., Irvin,
E., Daum, K.M., Gerr, F., Moore, J.S., Cullen, K.
& Rempel, D. 2006, "Workplace interventions
to prevent musculoskeletal and visual symptoms
among computer users: A systematic review",
Journal of Occupational Rehabilitation, vol. 16, pp.
Clark, B.C., Thomas, J.S., Walkowski, S.A. &
Howell, J.N. 2012, "The Biology of Manual
Therapies", Journal of American Osteopathic
Association, vol. 112, no. 9, pp. 617-629.
Cleland, J.A., Fritz, J.M., Whitman, J.M. &
Palmer, J.A. 2006, "The reliability and construct
validity of the Neck Disability Index and patient
specic functional scale in patients with cervical
radiculopathy", Spine, vol. 31, no. 5, pp. 598.
Dainoff, M.J., Cohen, B.G. & Dainoff, M.H.
2005, "The effect of an ergonomic intervention on
musculoskeletal, psychosocial, and visual strain
of VDT data entry work: the United States part of
the international study", International journal of
occupational safety and ergonomics: JOSE, vol. 11,
no. 1, pp. 49-63.
European Agency for Safety and Health at Work
2005, Ofce Ergonomics Council Directive 90/270/
EEC - European Agency for Safety and Health at
Work [Homepage of EEC], [Online]. Available:
efact13 [2011, 2011/07/20].
Falla, D.L., Jull, G.A. & Hodges, P.W. 2004,
"Patients With Neck Pain Demonstrate Reduced
Electromyographic Activity of the Deep
Cervical Flexor Muscles During Performance
of the Craniocervical Flexion Test", Spine,
vol. 29, no. 19, pp. 2108-2114 10.1097/01.
Gajasinghe, S., Wijayaratna, M. & Abayadeera,
A. 2010, "Correlation between numerical rating
scale (NRS) and visual analogue scale (VAS) in
assessment of pain in post operative patients", Sri
Lankan Journal of Anaesthesiology, vol. 18, no. 2,
pp. 81-83.
Gay, R.E., Madson, T.J. & Cieslak, K.R. 2007,
"Comparison of the Neck Disability Index and
the Neck Bournemouth Questionnaire in a sample
of patients with chronic uncomplicated neck
pain", Journal of manipulative and physiological
therapeutics, vol. 30, no. 4, pp. 259-262.
Grifths, K.L., Mackey, M.G. & Adamson, B.J.
2007, "The Impact of a Computerized Work
Environment on Professional Occupational Groups
and Behavioural and Physiological Risk Factors for
... One of the participants also showed an increase in productivity with both chairs. This implies that office chairs without adjustable armrests may be equivalent to more expensive fully adjustable chairs with respect to pain, muscle spasm and disability (Hoeben and Louw, 2014). ...
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With the emergence of work-related musculoskeletal disorders and the associated high cost of injured workers, physical therapists are in a unique position to help employers manage these concerns through multidisciplinary injury prevention programs, education, ergonomics, on-site treatment, and return to work programs. The purpose of this paper, through a review of the literature, is to describe the effect that workplace injuries have on employees and the economic burden on employers. Furthermore, this paper will highlight the effectiveness a physical therapist can have in the occupational health setting as part of a multidisciplinary team on ergonomics, employee health, prevention of work-related musculoskeletal disorders, return to work programs, and on-site treatment interventions, such as therapeutic exercise and manual intervention. This review of the literature suggests that participation in ergonomics and on-site physical therapy treatment in the workplace (e.g., education, exercise, manual intervention) has a positive effect on decreasing work-related musculoskeletal disorders, decreasing costs associated with these injuries, increasing work productivity, and decreasing absenteeism and improving presenteeism amongst workers. It is important to ensure that payers, employers, and employees are aware of the crucial role physical therapists can play in occupational health. Physical therapists also need to advocate for their role in occupational health and offer expert care to workers in a nontraditional manner.
Conference Paper
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ABSTRACT An adjustable multipurpose table is a platform that is at waist level, and it works like a workbench. This table uses when working in metal fabrication with especially in welding. It is handy because it gives the welder a stable place to work and can provide squaring and measuring assistance. A previous study found some problems experienced by the respondents when using the welding table. Among the problems experienced are such as back pain, the table is too heavy, and no safety features. The objective of this study is to design a more efficient and user-friendly welding table. For methodology research, a pneumatic system is applied to adjust the height of the table. Next, we use lighter iron than usual, so it is easier to move. A survey has been done to identify the existing table's problems and things that need to be upgraded. As a result, the design of the adjustable multipurpose table makes worker easier to do the welding task. However, the disadvantage of the product is limited to the size of the table. The results presented here may facilitate improvements in the materials, size, and safety factors. Keywords: Adjustable multipurpose table, pneumatic, welding
Conference Paper
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Ergonomics and design are interrelated concepts. The realization of ergonomics is through design. Today, when it comes to furniture design, not only visuality, but also ergonomics, aesthetics, functionality, comfort, health and safety issues are considered. Furniture, which is an indispensable part of our daily life, takes place in all areas of human life and adds aesthetics, beauty and functionality to the environment. Ergonomics science deals with many fields such as engineering, health, medicine, business, etc. One of the areas where design and ergonomics concepts are important is the furniture sector. In this study, the importance of ergonomic factors in furniture design was examined and the relationship between design, furniture and ergonomics was investigated. For this purpose, a literature review on the furniture industry has been carried out, and the studies on the subject have been examined and the importance of these concepts in the sector has been emphasized.
The reconfigurable seating system is a flexible seating solution for transit vehicles that allows operators to change the configuration of the floor plan in a timely manner in order to accommodate change in needs. This project consists of three senior project teams each working on a component of the design: system, track & latch, and articulation. Descriptions of the responsibilities of each team will be discussed below.
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38 consecutive consenting patients undergoing donor nephrectomy via loin incision were studied and assessed for the severity of pain by using both NRS and VAS at the beginning of commencing post-operative analgesia and then 2, 6, 12 and 24 hour intervals respectively. Data were analyzed to identify the correlation between the scales. 157 readings for NRS and VAS were analyzed which showed Beta coefficient of 0.87 (p < 0.01) in linear regression. Pearson correlation for the association was 0.904(p < 0.01). Pearson correlation for the NRS and VAS values taken at 2 and 6 hour intervals were higher than the overall Pearson correlation (0.904), while the values taken at other intervals were lower. NRS which is less pain inducing in post-operative period has a strong linear association with VAS, thus can substitute for VAS in assessment of post-operative pain. The reliability of NRS is higher at the commencement of analgesia, at 2 and 6 hour intervals.
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Background Prolonged sitting has been associated with musculoskeletal dysfunction. For desk workers, workstation modifications frequently address the work surface and chair. Chairs which can prevent abnormal strain of the neuromuscular system may aid in preventing musculo-skeletal pain and discomfort. Anecdotally, adjustability of the seat height and the seat pan depth to match the anthropometrics of the user is the most commonly recommended intervention. Within the constraints of the current economic climate, employers demand evidence for the benefits attributed to an investment in altering workstations, however this evidence-base is currently unclear both in terms of the strength of the evidence and the nature of the chair features. The purpose of this study was to evaluate the evidence for the effectiveness of chair interventions in reducing workplace musculoskeletal symptoms. Methods Pubmed, Cinahl, Pedro, ProQuest, SCOPUS and PhysioFocus were searched. ‘Ergonomic intervention’, ‘chair’, ‘musculoskeletal symptoms’, ‘ergonomics’, ‘seated work’ were used in all the databases. Articles were included if they investigated the influence of chair modifications as an intervention; participants were in predominantly seated occupations; employed a pre/post design (with or without control or randomising) and if the outcome measure included neuro-musculoskeletal comfort and/or postural alignment. The risk of bias was assessed using a tool based on The Cochrane Handbook. Results Five studies were included in the review. The number of participants varied from 4 to 293 participants. Three of the five studies were Randomised Controlled Trials, one pre and post-test study was conducted and one single case, multiple baselines (ABAB) study was done. Three studies were conducted in a garment factory, one in an office environment and one with university students. All five studies found a reduction in self-reported musculoskeletal pain immediately after the intervention. Bias was introduced due to poor randomization procedures and lack of concealed allocation. Meta-analysis was not possible due to the heterogeneity of the data (differing population, intervention and outcomes across studies). Conclusion The findings of this review indicate a consistent trend that supports the role of a chair intervention to reduce musculoskeletal symptoms among workers who are required to sit for prolonged periods. However the amount, level and quality of the evidence are only moderate therefore we cannot make strong recommendations until further trials are conducted. The review also highlights gaps: for example in showing whether the effectiveness of a chair intervention has long-term impact, particularly with respect to musculoskeletal symptoms, as well as the recurrence of symptoms and the consequent cost of care.
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The aim of this study was to investigate whether perceived exertion, perceived comfort and working technique is associated with the incidence of neck and upper extremity symptoms among professional computer users. At baseline a self-administered questionnaire was distributed to 853 participants from 46 different work sites (382 men and 471 women) who, at baseline, had been free from neck and upper extremity symptoms during the preceding month. Work-related exposures, individual factors, and symptoms from the neck and upper extremities were assessed. Observations of working technique were performed by ergonomists using an ergonomic checklist. Incidence data were collected by means of 10 monthly questionnaires, asking for information on the occurrence of neck, shoulder and arm/hand symptoms. Perceived exertion was rated on a modified Borg RPE scale ranging from 0 (very, very light) to 14 (very, very strenuous). Perceived comfort was rated on a 9-point scale ranging from -4 (very, very poor) to +4 (very, very good) in relation to the chair, computer screen, keyboard, and computer mouse. The median follow up time was 10.3 months. The incidence of symptoms from the neck, shoulders and arm/hands were 50, 24 and 34 cases per 100 person years, respectively.Higher perceived exertion in the neck, shoulder or arm/hands was associated with an increased risk of developing symptoms in the corresponding body region. Moreover, a dose-response relationship between the level of exertion and the risk of developing symptoms was recorded for all three regions. There was an association between low comfort and an increased risk for neck symptoms, but not for shoulder and arm/hand symptoms, although a trend towards such an association (not statistically significant) could be seen. Working technique was, in this study, not associated with the risk of developing symptoms in any of the investigated body regions. There was a strong association between high perceived exertion and the development of neck, shoulder, and arm/hand symptoms. Moreover, there was an association between poor perceived comfort and neck pain. Surveillance of computer users may include perceived exertion and comfort to target individuals at risk for neck and upper extremity symptoms.
Study Design. A systematic review was conducted. Objective. To identify, evaluate, and compare standard scales for assessing neck pain or dysfunction. Summary of Background Data. The degree of a patients neck pain or dysfunction can be evaluated using standardized scales at the time of a clinical encounter or during the performance of clinical research protocols. The choice of a scale with the most appropriate characteristics, however, is always a challenge to clinicians and researchers. Methods. Articles concerning scales for functional evaluation of neck pain or dysfunction were identified by computer searching of MEDLINE (January 1966 to June 1999) and CINAHL (1985 to 2000), citation tracking using the Citation Index, hand searching of relevant journals, and correspondence with experts. Results. Five standard scales were found. Three scales were remarkably similar in terms of structure and psychometric properties: the Neck Disability Index, the Copenhagen Neck Functional Disability Scale, and the Northwick Park Scale. However, only the first instrument has been revalidated in different study populations. The Neck Pain and Disability Scale provides a visual template for collection of information, but its usefulness is limited if the questionnaire must be read to the patient. The Patient-Specific Functional Scale is very sensitive to functional changes in individual patients, but comparisons between patients are virtually impossible. Conclusions. The five scales identified in this study have similar characteristics. The Neck Disability Index, however, has been revalidated more times for evaluation of patient groups. For individual patient follow-up evaluation, the Patient-Specific Functional Scale has high sensitivity to change, and thus represents a good choice for clinical use. The final choice should be tailored according to the target population and the purpose of the evaluation.
This literature review of ergonomic intervention studies aims to identify effective ergonomic interventions for improved musculoskeletal health in the workplace and to make recommendations for quality criteria in ergonomic intervention research. To avoid ambiguity in terminology a list of definitions of the ergonomic terms used in this paper is provided in an appendix. Models were developed for use in the classification of ergonomic intervention research and to illustrate the problems in interpreting ergonomic intervention data. The relevant literature was identified by a two-step process. First the relevant literature was identified by inclusion criteria, then, quality criteria were applied to identify studies of good quality for effective intervention. These appear to be firstly “organizational culture” and secondly modifier interventions, the former using multiple interventions with high stakeholder commitment to reduce identified risk factors, and the latter especially focusing workers at risk and using measures which actively involve the individual. A list of recommendations is provided.
Reviews the literature on the Hawthorne effect (HE) which originated out of the studies at the Hawthorne Works of the Western Electric Company. This effect is generally defined as the problem in field experiments that Ss' knowledge that they are in an experiment modifies their behavior from what it would have been without the knowledge. An examination of the Hawthorne studies conducted 50 yrs ago does not reveal this "effect" probably because there were so many uncontrolled variables. HE is inconsistently described in contemporary psychology textbooks, and there is lack of agreement on how the effect is mediated. Controls for the HE in current field research (mostly in education) took several forms, each designed for different purposes. In 13 studies designed to produce HEs, only 4 using adult Ss were successful. It is suggested that most persons in any clearly identified situation define the context for their behavior and respond accordingly; the necessity to ascertain Ss' view of the experiment requires different procedures than those typically used to control for HEs in the past. It is concluded that better articulation of how to adapt postexperimental questioning procedures to a diversity of experimental settings is needed. (68 ref) (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Each year, more than 18 million adults in the United States receive manual therapies, at a total annual out-of-pocket cost of $3.9 billion. Although there is growing evidence supporting the efficacy of manual therapies, little is known about the mechanisms underlying these treatments. This lack of basic knowledge significantly limits the development of rational strategies for the use of these treatments and potentially hinders their acceptance by the wider scientific and health care communities. Many authors have hypothesized that manual therapies act by disrupting the pain-spasm-pain cycle, but relatively little experimental evidence has supported this hypothesis. The authors have tested this hypothesis and summarize their work on the biology of manual therapies.
Background Although visual display terminal (VDT) work has become a common task among office workers, surveys which would help to determine the allowable duration of daily VDT use are limited.Methods We investigated more than 25,000 workers three times over a 3-year period using a self-administered questionnaire. Three factors, namely mental, physical and sleep-related symptoms, were extracted by factor analysis. Adjusted means of each factor score were compared with the duration of daily VDT use by general linear model.ResultsPhysical symptoms score became higher with increasing duration of daily VDT use without a threshold effect. Mental and sleep-related symptom scores of the workers using VDT for more 5 hr/day were significantly higher than that of the groups using VDT for >1, 1–3, and 3–5 hr/day.Conclusions Duration of daily VDT use was linearly related to the physical symptom score, and was non-linearly related to mental and sleep-related symptom score with a threshold effect of 5 hr/day. Am. J. Ind. Med. 42:421–426, 2002. © 2002 Wiley-Liss, Inc.
Neck pain is becoming increasingly common throughout the world. It has a considerable impact on individuals and their families, communities, health-care systems, and businesses. There is substantial heterogeneity between neck pain epidemiological studies, which makes it difficult to compare or pool data from different studies. The estimated 1 year incidence of neck pain from available studies ranges between 10.4% and 21.3% with a higher incidence noted in office and computer workers. While some studies report that between 33% and 65% of people have recovered from an episode of neck pain at 1 year, most cases run an episodic course over a person's lifetime and, thus, relapses are common. The overall prevalence of neck pain in the general population ranges between 0.4% and 86.8% (mean: 23.1%); point prevalence ranges from 0.4% to 41.5% (mean: 14.4%); and 1 year prevalence ranges from 4.8% to 79.5% (mean: 25.8%). Prevalence is generally higher in women, higher in high-income countries compared with low- and middle-income countries and higher in urban areas compared with rural areas. Many environmental and personal factors influence the onset and course of neck pain. Most studies indicate a higher incidence of neck pain among women and an increased risk of developing neck pain until the 35-49-year age group, after which the risk begins to decline. The Global Burden of Disease 2005 Study is currently making estimates of the global burden of neck pain in relation to impairment and activity limitation, and results will be available in 2011.