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Research Article
Effects of the Computer Desk Level on the Musculoskeletal
Discomfort of Neck and Upper Extremities and EMG Activities in
Patients with Spinal Cord Injuries
Bo-Ra Kang ,
1
Jin-Gang Her ,
2
Ju-Sang Lee ,
3
Tae-Sung Ko,
4
and Young-Youl You
5
1
Department of Occupational Therapy, Yonseimadu Hospital, Goyang, Republic of Korea
2
Department of Rehabilitation Therapy, Graduate School of Hallym University, Chuncheon, Republic of Korea
3
Department of Physical Therapy, Hallym Polytechnic University, Chuncheon, Republic of Korea
4
Department of Physical Therapy, Daewon University College, Jecheon, Republic of Korea
5
Department of Physical Therapy, Bronco Memorial Hospital, Hwaseong, Republic of Korea
Correspondence should be addressed to Jin-Gang Her; jghur7@empas.com
Received 5 September 2018; Accepted 24 December 2018; Published 3 February 2019
Guest Editor: H. S. Chhabra
Copyright © 2019 Bo-Ra Kang et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background. Computers are used as a means of social communication, for work and other purposes. However, patients with spinal
cord injuries may have a higher risk than normal individuals with musculoskeletal problems when using computers owing to their
inability to control respective postures due to problems in motor and sensory functioning. Objectives. This study is aimed at
identifying the effect of computer desk heights on musculoskeletal discomforts of the neck and upper extremities and EMG
activities in patients with spinal cord (C6) and upper thoracic spinal cord injuries. Methods. Participants of the present study
were the patients diagnosed with ASIA A or B. The patients were divided into two groups according to their spinal cord
injuries: C6 group and T2-T6 group. The level of the desk was set at 5 cm below the elbow, at the elbow level, and 5 cm above
the elbow level. Electromyography was used to measure the duration of typing task EMG(%RVC) of the cervical erector spinae,
upper trapezius, anterior deltoid, and wrist extensor. Subjective musculoskeletal discomfort (Borg-RPE) was measured at the
end of the experiment. Results. The two groups showed differences in terms of RPE corresponding to each level of the computer
desk (p<05). Postanalysis revealed the C6 group had decreased RPE as the level of computer desk increased, whereas the
subjects in the T2-T6 group had decreased RPE values in accordance with the decreasing level of computer desk (p<05). In
EMG, both groups had no significant differences (p>05). However, in terms of the interaction between the muscles and the
level of computer desk in both groups, the differences in the interactions of the upper trapezius and wrist extensor with each
level of the desk were found (p<05). Conclusion. This study is meaningful in that it confirms computer work posture and
preference of spinal cord-injured individuals.
1. Introduction
The global incidence of spinal cord injury shows an increas-
ing trend every year. Approximately one-third of patients
with spinal cord injuries also have tetraplegia, wherein
approximately 50% of the patients have complete injuries
[1, 2]. The injuries are mainly due to various accidents,
including the increasing incidence of industrial accidents;
the increase in the number of patients is also ascribable to
advancements in medical science which have resulted in
increased cases of the survival of patients with disabilities
[3]. Spinal cord injury is typically accompanied by neurople-
gia of the motor and sensory nerves as well as various phys-
ical disorders [4]. Spinal cord injury is an injury in the
central nervous system, which is difficult to completely treat.
Rehabilitation of patients with spinal cord injuries necessi-
tates biomedical and complementary approaches simulta-
neously with sociocultural approaches [5].
The number of working environments involving inter-
faces with computers has been increasing recently, wherein
Hindawi
Occupational erapy International
Volume 2019, Article ID 3026150, 10 pages
https://doi.org/10.1155/2019/3026150
the majority of employees spend an average of 7 hours a day
working at the interfaces to complete their work [6]. Individ-
uals with disabilities are able to work and socialize using
computers [7, 8]. Along with the increase in the number of
computer users, the number of patients with neck and shoul-
der pains and problems in the musculoskeletal system, such
as carpal tunnel syndrome, has also been increasing [9, 10].
Studies determining the proper ergonomic postures fit for
individuals with sedentary work, such as those work involv-
ing computers, have been increasing lately [11]. However,
most studies that explored proper ergonomic postures
required for working with computer interfaces have been car-
ried out in the European and North American environment,
thereby the results of such studies may not comply with
physical conditions of Asian people. In particular, the results
may not be suitable for Asian people relying on wheelchairs
[12]. For patients with spinal cord injuries, the risk of muscu-
loskeletal problems resulting from the use of VDTs would be
higher than normal people owing to the difficulty in dimin-
ishing static load or controlling respective postures wherein
respective patients would have different postures with which
they feel comfortable [12–14]. Currently, the majority of
studies have involved healthy individuals, and the number
of studies investigating the proper postures required when
using computers or preferences of patients with spinal cord
injuries is insufficient.
Therefore, the present study is aimed at identifying the
effects of computer desk heights on musculoskeletal discom-
fort of the neck and upper extremities and EMG (electromy-
ography) activities of patients with spinal cord (C6) and
upper thoracic spinal cord injuries (T2-T6).
2. Methods
2.1. Participants. A total of 12 patients admitted to the
Y-rehabilitation Hospital located in Gyeonggi-do province
from January 17 to January 26, 2018, were included in the
present study. They were divided into the following two
groups according to the level of spinal cord injury: C6 group
(six patients) and T2-T6 groups (six patients).
The inclusion criteria were as follows: (1) patients diag-
nosed as having complete injuries of motor function of the
types of either ASIA A or B defined by the American Spinal
Injury Association (ASIA) without cerebral injuries and
complications such as bone fracture or bedsores [15–17];
(2) male sex to eliminate differences in physical measure-
ments attributable to different sexes [18]; (3) right-handed;
(4) over 0.8 corrected vision; (5) normal range of articular
motion of the upper extremities; and (6) understood the pur-
poses of the present study and provided informed consent to
participate in the present study [17].
2.2. Experimental Method. The study protocol was approved
by the IRB of Hallym University (no. HIRB-2017-064) and
adhered to the ethical principles of the Declaration of Hel-
sinki. The computer used for the study had a 21-inch moni-
tor with adjustable levels, wherein the top of the monitor was
set at the patient’s eye level. The distance from the monitor to
the eyes of the patients was set at 70 cm, rather than the
recommended range of 63 to 93 cm, in consideration of the
patients’physical characteristics as subjects and their posi-
tions were each monitored into account [19]. Keyboards used
for the experiment were the standard ones. The keyboards
were placed on each desk with “G”and “H”keys placed at
the center of each patient and with a keyboard slope angle
of 3
°
, which was set as the default angle [20]. Based on the
study on subjective preference and fatigability of spinal
cord-injured patients who use wheelchairs, the height of the
keyboard was set to 5 cm below the elbow, the height of the
elbow, and 5 cm above the elbow [12], and the height adjust-
able desk were used for the matter of the heights [21]. The
participants were allowed to use their wheelchairs for the
experiment. Participants were asked to sit at 90
°
-110
°
hip
joint angle and over 90
°
knee joint angle [17]. For the C6
group, the “bend-type typing device”was used [7]. The par-
ticipants were asked to type for two minutes; a metronome
was used to eliminate the effects resulting from the partici-
pants’different typing speeds. A simple typing task was
introduced to minimize the factors affecting EMG activities
of the participants, which could lead to psychological reac-
tions of each subject who might be unfamiliar to the working
environment and input data [22, 23]. The subjects were asked
to use their right hand to enter “J,”“K,”and “L”keys, while
their left hand were supposed to type the “A,”“S,”“D,”and
“F”keys, simultaneously. The participants were asked to per-
form the typing task three times with one-minute rest time
between the typing tasks at identical keyboard level. The
sequence set to complete the typing tasks of each subject
was determined randomly. Five minutes of time for resting
upon completion of each typing task with the given posture
was allowed for each subject. The participants freely placed
their arms on their legs during the rest time [17]. Moreover,
the participants were instructed not to put their wrists and
forearms on the computer desk to eliminate the effects
resulted from the support of the lower arms during the given
typing task [17] (Figure 1). The subjective musculoskeletal
discomforts in the cervical erector spinae, upper trapezius,
anterior deltoid, and wrist extensor were measured using
the “Rating of Perceived Exertion Scale,”and EMG activities
of the neck and upper extremities of the subjects corre-
sponded to the varied positions of the keyboard. The cervical
erector spinae and upper trapezius frequently exhibit muscu-
lar pains and diseases resulting from an accumulation of
myalgia. The muscles used in long durations would cause
musculoskeletal problems due to the muscles being activated
continuously to maintain the static postures required [24]. In
individuals doing repetitive typing tasks using the hands and
arms, the musculoskeletal diseases would arise from the arm,
shoulder girdle, and wrist [25, 26]. In particular, the anterior
deltoid would be affected by the level of the keyboard. More-
over, the continuous repetitive tasks would result in muscu-
loskeletal problems in the wrist extensor [17] Thus, the four
muscles, which are likely to have frequent problems in indi-
viduals working on computers, were evaluated in this study.
Furthermore, the Borg-RPE (Rating of Perceived Exertion)
scale was employed for the measurement of musculoskeletal
discomforts of the neck and upper extremities. The RPE scale
spanned the range from “no pain at all”to “maximal pain”
2 Occupational Therapy International
[27]. The scores ranged from 6 points (the minimum) to 20
points (the maximum), with the lower scores indicating less
discomfort [28]. The scores were obtained from self-report
checklists distributed to each subject upon completion of
the experiment.
2.3. Data Collection. During the task, EMG measurement was
performed using a wireless EMG system (Wave EMG Infinity
Waterproof, Cometa System Inc., Italy) (Figure 2). Adhesive
dual electrodes of Ag-AgCl type, which were fixed 2 cm apart,
were used as surface electrodes. The “visual-3D”was used for
its analysis. The sampling rate was set at 2,000 Hz for electro-
myogram signals. The frequency range was set at the interval
of 30-250 Hz for the band-pass filtering. The measured sig-
nals of electromyogram were rectified and then smoothed
by employing the “Root Mean Square (RMS)”method [29].
While the participants were performing the typing task, the
electrodes were attached to the right cervical erector spinae,
upper trapezius, anterior deltoid, and wrist extensor, based
on the SENIAM (Surface ElectroMyography for the Nonin-
vasive Assessment of Muscles) instructions [30] (Figure 3).
The measurements of the electromyogram signals, collected
during the typing task, were standardized according to the
muscular contraction of specified muscles, also termed “Ref-
erence Voluntary Contraction (RVC)”. These values were
then standardized as %RVC [31, 32]. RVC of the neck muscle
was measured by asking the participants to wear a 0.3kg hel-
met and to maintain their posture with the head erected for
10 seconds. RVC of the shoulder muscle was measured by
asking participants to wear a 0.3 kg sandbag on their right
wrist. RVC of the upper trapezius was measured with the
patient’s arm abducted at 90
°
for 10 seconds, whereas the
RVC of the anterior deltoid was measured with the arm bent
at 90
°
. RVC of the wrist extensor was measured by asking the
patient to carry a 0.3 kg dumbbell with the wrist maximally
extended for 10 seconds [25]. The pads were attached by a
single person through the experiment to reduce errors in
the measurement of electromyogram. Electromyograms,
obtained from varied measurement durations of 100 seconds
to 300 seconds, are used for various purposes and tasks
reported in previous studies [17, 33]. In the present study, a
simple task was used in consideration of patients with spinal
cord injuries. The duration was set at 140 seconds, wherein
the electromyogram obtained from the duration of 120 sec-
onds which resulted from an exclusion of 10 seconds at both
ends of the interval was used for the analyses conducted in
(a) (b)
(c)
Figure 1: Desk height.
3Occupational Therapy International
the present study [23, 34]. In addition, musculoskeletal dis-
comforts were measured upon completion of all experiments
using the self-report checklist and the RPE Scale [28].
2.4. Data Analysis. The PASW 22.0 (IBM/SPSS Inc.,
Chicago, IL) for Windows was used for the statistical
analyses. The patients’general characteristics, such as the
age, height, weight, sitting eye level, and sitting elbow height,
were expressed in mean values and standard deviations,
whereas the date of onset of spinal cord injury, ASIA scale,
and level of injuries were expressed in percentage. An
ANOVA was carried out to analyze the musculoskeletal
(a) (b)
Figure 2: EMG measuring tools.
(a) (b)
(c)
Figure 3: EMG attachment part (posterior, lateral, and anterior view).
4 Occupational Therapy International
discomfort corresponding to the different levels of the com-
puter desk to determine the correct level of computer desk
corresponding to each level of injury. Values of %RVC for
the four muscles of subjects which corresponded to each level
of the computer desk were analyzed by conducting a two-way
ANOVA for repetitive measurements. The significance level
was set at α=005. The postanalytic Dunn-Bonferroni proce-
dure was used to perform multiple comparisons of the vari-
ables found to be statistically and significantly different.
3. Results
3.1. General Characteristics of the Patients. The details of the
general characteristics of the subjects are summarized in
Table 1.
3.2. Correlation of the RPE Values and Computer Desk
Height. A significant difference in terms of an indicator of
physical discomfort, which varied by different levels of the
keyboard of the subjects in the two groups, was found
(p<05) (Table 2). The RPE value of the patients in the C6
group decreased when the computer desk height was
increased (p<05), whereas, in the T2-T6 group, the RPE
value decreased when the computer desk height was
decreased (p<05). In particular, the RPE values of the
T2-T6 group were significantly different in the following
computer desk levels: (1) between the 5 cm below the elbow
level and elbow level and (2) between the 5 cm above the
elbow level and 5 cm below the elbow level (p<05). How-
ever, the RPE values in the computer desk level between the
level of the elbow and 5 cm above the elbow level had no sig-
nificant difference (p>05) (Table 3).
3.2.1. Correlation between the EMG of Patients and the
Varied Keyboard Positions. The correlations between the
EMG activities of the four muscles and the three different
keyboard positions were analyzed. No significant differences
in EMG activities of the four muscles were found between the
different levels of the computer desk (p>05) (Table 4).
3.2.2. Correlation between the Interactions of the Four
Muscles and the Various Computer Desk Levels. The correla-
tions between the interactions of the four muscles and the
three different computer desk levels were analyzed. Signifi-
cant differences were found in the interactions of the upper
trapezius and wrist extensor (p<05) (Table 5).
4. Discussion
In the present study, we investigated the effects of the varied
keyboard positions and computer desk heights on musculo-
skeletal discomforts and EMG activities of patients with spi-
nal injuries who were asked to perform a typing task on a
computer, with the goal of identifying the proper keyboard
position and computer desk level for these patients to prevent
the occurrence of musculoskeletal problems.
Factors that affect the neck and shoulder muscle tension
when handling the tasks involving the use of the keyboard
include: first, the incline of the thoracic spine and lumbar
spine; second, the posture of the cervical vertebrae; third,
the posture of the upper arm; fourth, the position of the key-
board and design; and fifth, computer-working skills and
break between the work [35]. In particular, for desk height,
most biotechnologists recommend that the position of the
“home”button should be placed 3 cm above the elbow during
elbow joint flexion, but another study suggests 8 cm [36]. In
addition, there is a study showing that the damage to the neck
and shoulder areas is from higher positions of the keyboard
and monitor and that the keyboard should be positioned
below the elbow [37]. However, the criteria for these table
heights are for the normal person. In a study of patients
who use the wheelchair, the study examined the subjective
preference and fatigability of users over 5 cm and below
5 cm based on the elbow height and found that spinal
cord-injured patients prefer the keyboards that were located
at the height of the elbow or below 5 cm [12]. In the case of
a normal person, muscle activity was doubled when working
on the table that is 5 cm higher than an elbow-high table.
Also, [23] when the location of the keyboard is below the
elbow, it reduces the risk of getting damage on the neck
and shoulder areas [38]. However, an objective study on
whether these results appear the same for spinal
cord-injured patients using wheelchairs was needed, so the
5 cm above and below presented in the preceding studies
were set to the keyboard height based on the elbow height.
The results of the study showed that the significant differ-
ences are found between the RPE values and the varied com-
puter desk levels in both patient groups. Our results were
similar to the findings of a previous study involving patients
with upper thoracic spinal cord injury who were using wheel-
chairs which sought to identify subjective preference and
degree of fatigue when working on computers with various
desk heights similar to ours. Their patients preferred the desk
height level of 5 cm below the elbow level [12, 28]. The
decrease in the RPE values was considered to be attributed
to the muscular tension of the neck and shoulder, which
increased when the desk level increased, thereby resulting
in tensional neck syndrome and discomfort [20, 34]. How-
ever, in the patients with complete injuries of C6, whose fin-
ger functions and wrist flexion, as well as the trunk and lower
extremity functions are lost, reduced balancing capability
occurs [7, 39]. In particular, the injury of the spinal cord
would decrease the capability of the trunk adjustment signif-
icantly compared to the injury of the thoracic spinal cord [16,
40]. Thus, the reduced musculoskeletal discomfort of the
patients with spinal cord injuries might be due to the stability
of their trunk, which is increased when the computer desk
height is increased.
In the International Standards for Neurological Classifi-
cation of Spinal Cord Injury (ISNCSCI), the seriousness of
the injury is described by using ASIA Impairment Scale.
The most severe grade AISA A is considered AISA A because
the sensory or motor function is not maintained in the spinal
cord S4-5 because the sensor is completely lost [41]. In par-
ticular, in the case of a motor function, they only existed
within the neck muscle and major muscles from the upper
extremity deltoid, elbow flexor, and wrist extensor when the
cervical spinal nerve 6 is completely damaged. If hydrothorax
2-6 is completely damaged, the muscles in the neck and the
5Occupational Therapy International
abdomen will remain the same, but the tension in the abdom-
inal muscles will decrease [16]. In the case of the spinal
cord-injured patients, especially the upper level, they show
a noticeable back bend in the sitting posture and, in reaction
to this, a straighten neck position [42]. Therefore, this study
selected the cervical erector spinae and upper trapezius as
an experimental muscle because their muscle activity influ-
enced a lot due to reducing in the trunk’s tension that is for
maintaining posture during handling task [43, 44]. In addi-
tion, 90% of cumulative trauma disorders that comes from
the use of VDT are related with upper extremities [45]. In
particular, disease from the hand and wrist showed the great-
est frequency, followed by the neck, arms and shoulders [46].
The form of standardized keyboard requires hyperextension
of the wrist joint, and the work station’s location requires lift-
ing the upper arm which leads to tiredness of deltoid [45].
Therefore, the wrist extensor and deltoid that influence a
lot by the form of keyboard and the height of desk when han-
dling the task were selected as experimental muscles.
Moreover, the effects of the different keyboard positions
on EMG activities of patients with spinal cord injuries during
the typing task were explored. No significant differences were
found between the varied keyboard positions and EMG activ-
ities. The Occupational Safety and Health Administration
(OSHA) of the United States of America recommends that
the appropriate keyboard position should be from 70
°
to
135
°
of elbow flexion. However, these recommended levels
are only applicable in healthy individuals; hence, studies
investigating the effects of computer desk level of work table
on the upper extremities, necks, and shoulders of patients
with spinal cord injuries using wheelchairs are warranted
[47]. Furthermore, the correlation between the four muscles
and the different computer desk levels was analyzed. The sig-
nificant differences were found in interactions of the two
muscles of upper trapezius and wrist extensor of the subjects
in both groups with the varied level of the computer desk,
which might be attributable to the effects of the level of com-
puter desk over the upper trapezius of which major function
was originally supposed to raise the scapula [48]. In addition,
the wrist extensor of the patients in the C6 group was found
to be affected more by the varied levels of the computer desk
than those in the T2-T6 group, which might be due to their
difficulty in controlling their forearm because of the complete
loss of finger functions, partial loss of wrist joint functions,
and weak pronator and supinator [49, 50]. Moreover, as the
wrist extensor and anterior deltoid were found to be affected
significantly by the varied positions of the keyboard as
Table 1: General characteristics of the subjects (n=12).
(a)
Classification C6 group (n=6)M±SD pT2-T6 group (n=6)M±SD p
Age (years) 33 8±150.041 53 3±130.097
Height (cm) 174 7±70.918 172 0±5 9.497
Weight (kg) 75 1±93.708 70 8±113.567
Eye height in sitting position (cm) 127 8±476 .305 122 9±4 5.166
Elbow height in sitting position (cm) 74 8±38.196 73 3±2 9.111
(b)
Classification C6 group (n=6) T2-T6 group (n=6)
Number (n) Percent (%) Number (n) Percent (%)
Onset (year)
Less than 1 1 16.7 4 66.7
1 to 2 4 66.7 2 33.3
2 or over 1 16.7 0 0
ASIA
A 5 83.3 3 50
B 1 16.7 3 50
Level of injury C6 (n=6) C6 (100) T2 (n=3), T6 (n=3) T2 (50), 6 (50)
∗p< 05 and values are n(%) or mean ± standard deviation.
Table 2: Correlation between RPE and computer desk height
(n=12).
Desk height Body part discomfort
rating (RPE) pF
C6
5 cm below 15 33 ± 1 50
∗.000 17.245Same as 13 00 ± 1 26
5 cm above 10 33 ± 1 63
T2-T6
5 cm below 10 33 ± 1 03
∗.001 12.297Same as 12 33 ± 1 03
5 cm above 14 00 ± 1 67
∗p<005.
6 Occupational Therapy International
reported previously, the significant difference in the interac-
tion between the function of wrist extensor and varied level
of computer desk could be ascribable thereto [17, 34, 50].
The population of disabled people in Korea was esti-
mated to be approximately 2,510,000 in 2014, wherein the
individuals with spinal cord injuries account for 4.9% of the
population with limb and body disabilities [51]. Hence, their
quality of life has received much attention, which is reflected
by several previously conducted studies. Factors affecting the
quality of life of these patients include level of economic sta-
tus, sex life, social support, the feeling of helplessness, depres-
sion, the degree of performance in daily living, occupational
activities, and mobility, among others [52]. In particular,
the availability of the Internet was found significantly associ-
ated with the quality of life; the emotional states, physical
states, a functional domain, economic life, and self-esteem
were also found significantly associated with their quality of
life [53]. In terms of the disability resulting from the spinal
cord injury, tetraplegia due to injuries in the cervical spinal
cord would be more serious than paraplegia due to the tho-
racic spinal cord injury [54], thereby the tetraplegic patients
need auxiliary tools when working on computers and envi-
ronmental provisions [17]. However, only a few studies
investigated on the working conditions, relating to computer
use, of patients with spinal cord injuries. Considering the
current situations, wherein engineering approaches employ-
ing computers to assist patients with cervical spinal cord
injuries are increasing, the present study would be significant
because it provides objective experiments employing EMG
activities and indicators of subjective musculoskeletal dis-
comfort on the varied desk levels.
The study had several limitations. First, the study has a
small sample size. Second, the representativeness of the
included patients was difficult to secure despite the
Table 3: Posthoc analysis of the musculoskeletal discomfort and desk height (n=12).
Group Desk height MD SE p
Body part discomfort rating (RPE)
C6
5 cm below Same as 2.333 .852 ∗.046
5 cm below 5 cm above 5.000 .852 ∗.000
Same as 5 cm above 2.666 .852 ∗.021
T2-T6
5 cm below Same as −2.000 .740 ∗.049
5 cm below 5 cm above −3.666 .740 ∗.001
Same as 5 cm above −1.666 .740 ∗.119
∗p<005; MD: mean difference; SE: standard error.
Table 4: Comparison of the EMG of the 2 groups of subjects corresponded to varied positions of keyboard (n=12).
C6 group
Keyboard position (n=6)
T2-T6 group
Keyboard position (n=6)
Elbow flexion pX2/FElbow flexion pX2/F
5 cm elbow Same as 5 cm above 5 cm below Same as 5cm above
CES 277 27 ± 125 27 301 79 ± 146 10 303 67 ± 152 70 .810 .422 187 05 ± 68 29 420 94 ± 555 51 231 23 ± 84 19 .440 .868
UT 11 38 ± 10 78 16 32 ± 16 55 17 31 ± 21 99 .458 .796 22 71 ± 10 03 32 36 ± 18 16 41 23 ± 21 11 .135 4.012
AD 19 43 ± 9 11 19 42 ± 7 62 19 42 ± 7 78 .910 .188 21 20 ± 9 05 21 39 ± 7 86 24 19 ± 11 57 .692 .737
WE 53 32 ± 19 83 54 75 ± 22 15 59 43 ± 20 81 .611 .986 33 08 ± 15 08 31 80 ± 13 99 34 56 ± 12 27 .849 .327
∗p< 05; CES: cervical erector spinae; UT: upper trapezius; AD: anterior deltoid; WE: wrist extensor.
Table 5: Comparison of interactions of the four muscles of subjects in the two groups with the varied levels of the computer desk (n=12).
Desk
CES interaction
(group × desk)
UT interaction
(group × desk)
AD interaction
(group × desk)
WE interaction
(group × desk)
M±SD pF M±SD pF M±SD pF M±SD pF
C6
5 cm below 277 28 ± 125 27
.629 .585
11 38 ± 10 78
∗.013 4.196
19 43 ± 9 11
.758 .394
53 32 ± 19 83
∗.006 4.989
Same as 301 79 ± 146 10 16 33 ± 16 55 19 42 ± 7 62 54 76 ± 22 15
5 cm above 303 67 ± 152 70 17 31 ± 21 99 19 42 ± 7 78 59 44 ± 23 75
T2-T6
5 cm below 187 05 ± 68 29 22 71 ± 10 03 21 20 ± 9 05 33 08 ± 15 08
Same as 420 94 ± 555 51 32 37 ± 18 16 21 39 ± 7 86 31 81 ± 13 99
5 cm above 231 24 ± 84 19 41 23 ± 21 11 24 19 ± 11 57 34 57 ± 12 27
∗p< 05,mean ± standard deviation.
7Occupational Therapy International
homogeneity of the patient’s general characteristics to avoid
selection bias in the study participants. Third, the typing task
was a simplified short-run task, which was remarkably differ-
ent from the actual work performed in computers. Thus,
future studies with a large sample size and varied computer
task to examine EMG activities are warranted.
5. Conclusions
The RPE values, which represent the subjective measurement
of musculoskeletal problems of the upper extremities of the
patients in the C6 group, decreased at the computer desk
level of 5 cm above the elbow level, whereas the patients in
the T2-T6 group had decreased RPE values at the computer
desk level of 5 cm below the elbow. Moreover, the subjects
in both groups commonly exhibited no significant differ-
ences in EMG activities corresponding to the different levels
of the keyboard. However, the upper trapezius and wrist
extensor, among the four muscles, were found to be associ-
ated with the varied computer desk levels in both groups.
The appropriate computer working conditions should
be customized according to the need of the individual with
a disability.
Data Availability
The demographics and clinical data collected to support the
findings of this study are restricted by the Ethics Committee
of the Province of Hallym University (Republic of Korea)
in order to protect patient privacy. Data are available
from Bo-Ra Kang, Yonseimadu Hospital 123, Gangseok-ro,
Ilsandong-gu, Goyang-si, Gyeonggi-do, Republic of Korea
(violet781@nate.com), for researchers who meet the criteria
for access to confidential data.
Conflicts of Interest
The authors declare that they have no conflicts of interest.
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