Pain and Muscle Activity of Neck, Shoulder and Forearm Muscles
during Touch-screen Tablet Use
on the Lap, on the Table, and on the Table with a Case Set
PattariyaIntolo *,
DuangsamonKeawroongreaung,
OnumaRushaneepun,
and
HathaishanokPoolnoi
Faculty of Health Sciences, Srinakharinwirot University, Thailand
Background: The touch-screen tablet has become a widely used portable computing device
globally. However, physical ergonomics parameters such as muscle activity and pain during
use have yet to be evaluated.
Objective: To determine pain and muscle activity at neck, shoulder, upper back and forearm
regions during tablet use on the lap, table, and table with a case set among university
students.
Methods: Twenty-four female experienced tablet users aged 18-25 years old completed
simulated tasks with tablets in three typical user configurations: on the lap, table, and table
with case set at a 60-degree angle. Pain was measured using visual analog scale and body
pain chart. Muscle activity was measured using electromyography (EMG).
Results: Surprisingly, nearly 100 percent of participants reported pain after tablet use for 21
minutes in all three configurations. The highest severity of pain at the marked region was
found during tablet use on the lap compared with other two configurations. Pain at forearm
was clearly found in tablet use with the case set at high angle. EMG of cervical erector
spinae muscle in tablet use on the table and table with a case set were significantly higher
than that on the lap.
Conclusions: Tablets should be placed on the table to avoid neck pain during computing use.
However, tablet sat high angle can lead to pain at forearm region. Activity of neck muscle
was high during tablet use on the table. Ergonomic parameters of tablet use should be
evaluated in children and other age groups.
Keywords: tablet, pain, muscle activity
*
Corresponding Author:DrPattariyaIntolo PT, Ph.D. (Physiotherapy)
Faculty of Health Sciences, Srinakharinwirot University,
Ongkharak, Nakhon-Nayok, 26120, Thailand
Phone: (+66) 84944 5859 Fax: (+66) 37 395438
E-mail: pattariy@swu.ac.th
1 Introduction
Tablet computers have recently become very popular in the global computer market
with increases of U.S. Internet users owned a tablet from 12% in 2011 to 31% in 2013
(Moscaritolo, 2013). The mobility properties and easy to use touch-screen of a tablet are the
main reasons behind this trend. However, such properties allow the user to adopt a variety of
postures leading to health problems. In addition, the keyboard and displays are included in a
small screen compared to laptop and desktop computers which also leads to health problems.
Risk of musculoskeletal symptoms in computer users may relate to display position
and location of computer during usage. Pain at neck and shoulder were reported arising from
computer use among users (Bongers et al, 2006, Brandt et al, 2004, Hakala et al, 2006,
Janwantanakul et al, 2008, Siu e tal, 2009, Godl et al, 2011,). Positioning of computer and
location of display as relates to pain and muscle activity at neck and shoulder has been widely
examined (Psihogios et al, 2001, Siu et al, 2009, Straker et al, 2008, Gold et al, 2011, Young
et al, 2012).Increase in head neck flexion moment and cervical erector spinae muscle group
activity were found in lower display position (Villanueva et al., 1996, Turville et al, 1998,
Sommerich et al., 2001, Greig, Straker, & Briggs, 2005). Tablets were used in a wide variety
of locations including on the lap, table, on a case to set it at any angle, and holding it (Young
et al, 2012).
Guidelines for good ergonomics for tablet use –following investigations into physical
ergonomic parameters and neck and shoulder pain– need to be established urgently due to
increasing usage. Interestingly, pain and muscle activity at forearm region during tablet use
has not yet been evaluated even though it is active with a touch-display, differing from PC
and laptop computers.
The study aimed to evaluate the severity and location of pain and muscle activity at
the neck, upper trunk, shoulder and forearm regions after tablet use emailing, typing and
game playing for 21 minutes in three workstations, namely, on the lap, table and table with a
case set among university students aged 18-25 years old.
2 Methods
Study design
A within-participant design was used to examine the effect of three tablet
workstations on neck, and upper limb pain and muscle activity.
Participants
Females aged 18-25 years old were recruited into the current study (Table 1). The
participants used tablets twice a week for at least 2 hours per week. The exclusion criteria
included any history of pain at neck, shoulder and upper limb regions requiring clinical
treatment. All participants were right-hand dominant and had normal or corrected-to-normal
vision. The present study was approved by the Human Ethics Committee of Health Science
Faculty, Srinakarinwirot University.
Table 1
Anthropometric values for 24 female participants.
Participants Age
Mean
Standard
Range
Height
Body mass index
Body height
(kg/m2)
(yr)
(cm)
21.2
160.6
20.5
84.88
5.7
1.5
7.19
18-23
73-93
1
18-25 150-175
(cm)
Independent Variables
The position of tablet (size 9.5x7.3x0.4 inches) use was observed in university
students representing the three workstations of on the lap, table and table with a case set
(Figure 1). Participants sat on a standard chair and table commonly used in the university
with no adjustment of height and tilt. The location of tablet was placed directly in front of
participants2 inches from the edge of the table; this location was generally observed in this
group of students. In the laboratory, climate and light was controlled.
Figure 1 Three workstations a) on the lap b) on the table c) on the table with a case set at 60degree tilt
Tasks
The three tasks were: 1) internet searching and e-mail reading, 2) game playing, 3)
typing words; each task lasted7 minutes totaling21 minutes with a rest period between
workstations.
Dependent Variables
Location and severity of pain were measured with visual analog scale and body pain
chart (Mekhora et al, 2000). Level of pain was on a scale of 0-10 where 10 indicated extreme
pain and 0 no pain. Pain was divided into four levels: no pain (VAS=0-0.04), mild pain
(VAS=0.05-4.4), moderate pain (VAS=4.5-7.4), and severe pain (VAS=7.5-10) (Hawker et
al, 2011).
Surface electromyography was recorded from the right cervical erector spinae (CES),
right upper trapezius (UT), right thoracic erector spinae/scapular retractors (TES), and right
wrist extensor bundle (RWE). Pairs of 10-mm diameter Ag-AgCl disposable surface
electrodes (Uni-Patch, Wasbasha, MN) were placed 25 mm apart (center to center) after the
skin had been thoroughly prepared by shaving and cleaning. Location of surface electrode
and amplitude normalization to maximal voluntary contraction (MVC) was performed
(Straker et al, 2008). Raw EMG signals were collected via a four-channel AMT-8 EMG cable
telemetry system(Bortec Biomedical, Alberta, Canada) with analogue differential amplifiers
and sampled at 1000 Hz. Mean EMG activity over the last two minutes (20min-21 min) of
each workstation was utilized for analysis.
Procedure
Participants completed an informed consent form. Instruction of required workstations
and tasks was described. Maximum voluntary contraction of each muscle was collected.
Participants performed tablet use in three workstations in random order with 21 minutes for
each workstation and 15 minutes break between. Participants were asked to define location
and severity of pain on the body pain chart and visual analog scale immediately after
finishing tablet use in each workstation.
Statistical Analysis
The dependent variables were pain and muscle activity at the neck, shoulder, upper
back and forearm regions. The independent variables were the three workstations of tablet
use on the lap, table and table with a case set. Intensity of marked pain regions and overall
pain intensity were calculated for the mean and standard deviation, and number of anatomical
pain regions marked was counted. To examine mean differences in EMG for the three
workstations, one-way ANOVA repeated measures with Bonferroni adjustment for alpha to
account for multiple comparisons was used with alpha level of .05.
3 Results
3.1 Pain in three workstations of tablet use
One hundred percent of participants(n=24/24) reported pain after emailing, playing
computer games, and typing for tablet use on the lap, while approximately ninety six percent
(n=23/24) reported pain in tablet use on the table and on the table with a case set (Table 1).
Participants experienced pain at a mean of 3.3-3.5 for the four overall regions (neck, upper
back, shoulder and forearm) after finishing tablet use in the three workstations. Average
intensity of pain in the regions marked for tablet use on the lap was highest with a pain level
of 4.4, while this was 3.1 and 2.5 for on the table and on the table with a case set,
respectively. Average overall intensities after tablet use on the lap, table and table with a case
set were 2.6, 1.9, and 1.6 respectively.
Table 1 Body region of pain of tablet use in 3 workstations (n=24)
Tablet use in
Pain
Number of
Intensity
Overall
in any body part
regions
of region
intensity
3 workstations
marked
Number of
Mean (SD)
Mean (SD)
Mean (SD)
participant (%)
On the lap
n=24 (100%)
3.5 (0.9)
4.4(2.2)
2.6 (1.5)
On the table
n=23 (96%)
3.5 (1.1)
3.1(2.0)
1.9 (1.4)
On the table with a case set
n=23 (96%)
3.3 (1.2)
2.5(1.9)
1.6 (1.5)
Interestingly, there were two participants reporting severe pain at neck after tablet use
on the lap, whereas there were no such participants for tablet use on the table and table with a
case set. In addition, the number of participants reporting moderate pain at neck was highest
when compared with the other two workstations (Figure 2).
The number of participants experiencing mild pain at upper back was similar for
tablet use on the table with case, on the table and on the lap at 16, 15 and 17 respectively.
However, 4 participants reported moderate pain at upper back after tablet use on the table,2
after tablet use on the lap, and none after tablet use on the lap with a case set.
The number of participants who experienced mild pain at shoulder after tablet use did
not differ for the three workstations: on the lap (n=19), table (n=20) and table with a case set
(n=19).
Interestingly, moderate pain at forearm was reported by participants using tablets on
the table with a case set, while there was only one report for on the table and none after tablet
use on the lap.
Pain at neck region
Number of participant (n=24)
20
20
18
15
12
10
5
0
3
1
2
0
on the table
with case
no pain
10
mild
4
moderate
0
on the table
0
2
severe
on the lap
Workstations
Figure 2 Pain at neck region after tablet use
On the table with a case set, on the table and on the lap
Table 2 Location of pain and severity of pain of tablet use in 3 workstations (n=24)
Location of pain: Number of participants experiencing pain.
Pain scale
No pain (VAS =0-0.04)
Neck
: n=0
Upper back :n=5
Shoulder
:n=2
Wrist
: n=6
Neck
:n=2
Upper back: n=5
Shoulder :n=2
Wrist
: n=3
On the table
with a case set
Neck
:n=3
Upper back: n=8
Shoulder :n=3
Wrist
: n=5
Mild pain (VAS =0.05-4.4)
Neck
:n=12
Upper back: n=17
Shoulder :n=19
Wrist
: n=18
Neck
:n=18
Upper back: n=15
Shoulder :n=20
Wrist
: n=20
Neck
: n=20
Upper back: n=16
Shoulder :n=19
Wrist
: n=17
Moderate pain (VAS =4.5-7.4)
Neck
:n=10
Upper back : n=2
Shoulder :n=3
Wrist
: n=0
Neck
:n=4
Upper back: n=4
Shoulder :n=2
Wrist
: n=1
Neck
:n=1
Upper back : n=0
Shoulder :n=2
Wrist
: n=2
Neck
:n=2
Upper back : n=0
Shoulder :n=0
Wrist
:n=0
Neck
:n=0
Upper back : n=0
Shoulder : n=0
Wrist
: n=0
Neck:
n=0
Upper back : n=0
Shoulder :n=0
Wrist
: n=0
Severe pain (VAS =7.5-10)
On the lap
On the table
Table 3EMG activity of 4 muscles of tablet use in 3 workstations (n=24)
EMG Muscle activity
(%Normalization)
Muscles
Workstations
On the lap
On the table
1. Wrist Extensor
15.47%± 11.08%
14.74%± 10.20%
On the table
With a case set
13.30% ± 5.91%
2. Cervical erector
spine
11.02% ± 6.24%
26.45%± 16.82%
20.44% ± 9.34%
3. Upper trapezius
16.15%± 11.00%
21.01%± 17.81%
25.39%± 19.17%
4. scapular retractors
10.82% ± 7.55%
12.80% ± 8.40%
12.18% ± 8.10%
P value
No significant difference
in all three workstations
Significant difference
Lap vs table (p<0.05)
Lap vs table with a case
set (p<0.05)
No significant difference
for table vs table with a
case set
No significant difference
in all three workstations
No significant difference
in all three workstations
Lap = tablet use on the lap, table = tablet use on the table, table with a case set = tablet use with a case set, vs =
versus
There was significant difference in EMG of cervical erector spinae between tablet use
on the lap and the table with p value of 0.05; for between tablet use on the lap and the table
with a case set this also stood at 0.05. However, there was no significant difference of EMG
of cervical erector spinae between tablet use on the table and table with a case set.
There was no significant difference for the other 3 muscles of wrist extensor, upper
trapezius, and thoracic upper trapezius and scapular retractors after tablet use in the three
workstations after 21 minutes.
4 Discussions
The purpose of the current study was to assess pain and muscle activity at neck, upper
trunk, shoulder and forearm after tablet use among university student for 21 minutes in three
workstations: on the lap, on the table and on the table with a case set. The results showed that
using tablets in different workstations affected various locations and severity of pain and
level of muscle activity. Generally, pain in any body part of the user, particularly neck pain
was reported in almost all participants after 21 minutes in all workstations. There was no
significant difference between the muscle activities of upper trapezius, scapular retractor and
forearm extensor muscles among all workstations; however, muscle activity of erector spinae
in tablet use on the lap was significantly higher than that on the table and table with a case
set.
It was clear that every participant reported neck pain after using tablets on their laps
for just21 minutes. In addition, intensity of pain in region marked and overall pain intensity
during tablet use on the lap was higher than the other two workstations. Surprisingly, 2
participants reported severe neck pain and 10 moderate neck pain after tablet use on the lap
for 21 minutes. This may be because the tablet was placed on the lap, which is much lower
than eye level. Moreover, tablet screens are generally small when compared with laptops and
desktops. To view the tablet screen properly, users need to be in a flexed neck posture,
leading to neck pain. The current study supported previous findings that working with a low
height screen leads to neck pain because of the flexed neck posture of the users (Gold et al,
2011).
It is noteworthy that almost all participants reported pain in at least one area (neck,
upper trunk, shoulder and forearm) following tablet use over a long period (21 minutes) on
the lap, table, and table with a case set. A previous study supports this finding; spending
longer time sitting on the computer leads to higher musculoskeletal pain (Jacob and Baker,
2002).The current study therefore suggests that frequent breaks be taken within in prolonged
tablet usage to reduce the risk of musculoskeletal problems.
This is the first study addressing the use of computer devices with touch screens and
pain and muscle activity at forearm region. Even though muscle activity of wrist extensor did
not significantly differ among all three workstations, tablet use on the table with a case set at
60 degrees clearly had a higher number of participants reporting moderate pain at forearm
compared with the other two workstations. No participants reported moderate pain at the
forearm after tablet use on the lap. Possibly, wrist posture was at a higher degree of extension
while working at a tablet with a case set at 60 degrees compared with on the lap. Obviously,
during tablet use, the wrist moves to the radial and ulnar sides while fingers move over a
wide range on the screen and zoom in/out – differing from wrist movements in typing on
keyboards and using mouses on desktops and laptops. Therefore, further study needs to
evaluate the pain and muscle activity of the wrist in radial and ulnar directions and fingers
while using tablets.
Surprisingly, the study found that neck erector spinae in tablet use on the lap was
significantly lower (p<0.05) than that on the table and table with case set. This may be
because during tablet use on the lap, the tablet was placed at the lowest level from eye level
compared with the other two workstations, students leaning their trunk backward to the chair
backrest with cervical flexion moment being reduced. In contrast, for tablet use on the table,
students sat upright and bent their necks forward to look at the screen on the table leading to a
high neck flexion moment related to high neck muscle activity (Fig 1). Further research is
needed to consider the effect of the position of upper and low trunks during tablet use for
creating guidelines for tablet use.
There was no difference in upper trapezius activity in the three workstations, which
concurs with previous studies (Aaras et al., 1997, Villanueva et al., 1997, Turville et al.,
1998, Sommerich et al., 2001, Fostervold et al., 2006) that found display height to have no
effect on trapezius activity. Straker et al (2008)found the mean muscle activity of the upper
trapezius in children during tablet use to be 21.6 %MVC, very similar to that for university
students for tablet use on the table in the current study (21.01 %MVC). However, the mean
muscle activity of erector spinae during tablet use in children was 38.0 %MVC (Straker et al,
2008) whereas for tablet use on the table in the current study it was 26.45 %MVC. This
difference in values can possibly be attributed to the age difference of participants. In a
previous study the muscle activity of cervical erector spinae in adults (18-25 years old) and
an older child (10-12years old) were lower than younger children (5-8 years old) during an
individual desktop workstation setup (Maslen and Straker, 2009).
5 Conclusions
Tablet use on the lap showed a higher intensity of pain in all regions especially neck
after working on a table for 21 minutes when compared with the other two workstations. The
number of regions of pain was also higher for tablet use on the lap. However, EMG activity
of ES in tablet use on the lap was significantly higher than the other two workstations. There
was no significant difference in EMG activity of UT, MT and wrist extensor among all three
workstations.
The ergonomic parameters of tablet use requires urgent investigation for
children and other age groups to prevent risk of musculoskeletal pain as the tablet is a rapidly
growing trend among IT users.
Acknowledgements
The authors would like to thank all of the participants for taking part in this study and
also special thanks to Stephen Lorriman for his support.
Conflict of interest
There is no other potential conflict of interest or the appearance of a conflict of
interest with regards to the study.
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