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 Height Body mass index Body height

(yr) (cm) (kg/m2) (cm)

Mean 21.2 160.6 20.5 84.88

Standard 1 5.7 1.5 7.19

Range 18-25 150-175 18-23 73-93

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 60-

degree 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

3 workstations

Pain

in any body part

Number of

regions

Intensity

of region

marked

Overall

intensity

Number of

participant (%)

Mean (SD) Mean (SD) Mean (SD)

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.

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

On the lap On the table On the table

with a case set

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

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

Severe pain (VAS =7.5-10) 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

0

5

10

15

20

on the tablewith case on the table

on the lap

3 2

0

20 18

12

1 4

10

0 0 2

Nu

mb

er o

f p

arti

cip

ant (

n=2

4)

Workstations

no pain

mild

moderate

severe

Pain at neck region

Table 3EMG activity of 4 muscles of tablet use in 3 workstations (n=24)

Muscles

EMG Muscle activity

(%Normalization)

Workstations

On the lap On the table On the table

With a case set

P value

1. Wrist Extensor 15.47%± 11.08% 14.74%± 10.20% 13.30% ± 5.91% No significant difference

in all three workstations

2. Cervical erector

spine 11.02% ± 6.24% 26.45%± 16.82% 20.44% ± 9.34% 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

3. Upper trapezius 16.15%± 11.00% 21.01%± 17.81% 25.39%± 19.17% No significant difference

in all three workstations

4. scapular retractors

10.82% ± 7.55% 12.80% ± 8.40% 12.18% ± 8.10% 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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