hand usage pattern and upper body discomfort of desktop touchscreen users

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This article was downloaded by: [University of Sydney] On: 01 September 2014, At: 20:05 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Ergonomics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/terg20 Hand usage pattern and upper body discomfort of desktop touchscreen users Hwayeong Kang & Gwanseob Shin a a Department of Human and Systems Engineering, Ulsan National Institute of Science and Technology, Ulsan, Korea Published online: 12 Jun 2014. To cite this article: Hwayeong Kang & Gwanseob Shin (2014) Hand usage pattern and upper body discomfort of desktop touchscreen users, Ergonomics, 57:9, 1397-1404, DOI: 10.1080/00140139.2014.924574 To link to this article: http://dx.doi.org/10.1080/00140139.2014.924574 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions

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This article was downloaded by: [University of Sydney]On: 01 September 2014, At: 20:05Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

ErgonomicsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/terg20

Hand usage pattern and upper body discomfort ofdesktop touchscreen usersHwayeong Kang & Gwanseob Shina

a Department of Human and Systems Engineering, Ulsan National Institute of Science andTechnology, Ulsan, KoreaPublished online: 12 Jun 2014.

To cite this article: Hwayeong Kang & Gwanseob Shin (2014) Hand usage pattern and upper body discomfort of desktoptouchscreen users, Ergonomics, 57:9, 1397-1404, DOI: 10.1080/00140139.2014.924574

To link to this article: http://dx.doi.org/10.1080/00140139.2014.924574

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

Hand usage pattern and upper body discomfort of desktop touchscreen users

Hwayeong Kang and Gwanseob Shin*

Department of Human and Systems Engineering, Ulsan National Institute of Science and Technology, Ulsan, Korea

(Received 27 August 2013; accepted 5 May 2014)

A laboratory study was conducted to determine how users of different handedness interact with desktop touchscreendisplays and how the hand usage pattern influences their body discomfort development. Twenty-one participants in threedifferent handedness groups conducted simple web-browsing for 30 minutes using a 2300 touchscreen display while theirsubjective body discomfort, frequency of use of each hand and touch area preference were periodically quantified.Participants reported a gradual increase in body discomfort during web-browsing, and the increments in body discomfortvaried between handedness groups for some body parts. Results also show that right-handed participants had strongerlaterality than the left-handed, and ambidextrous participants used both hands more evenly than other participants,suggesting associations between the hand usage pattern and body discomfort development. Findings of the current studysuggest that body discomfort of desktop touchscreen display users could be moderated by user-interface improvements anduser training.

Practitioner Summary: Body discomfort development of desktop touchscreen users may be influenced by their hand usagepattern. Findings of this laboratory study suggest that user discomfort may be moderated by placing menu items in the lowerarea within the display or training users to alternate hands when conducting touch gestures.

Keywords: touchscreen; touch interface; handedness; hand preference; body discomfort

1. Introduction

Finger touch interfaces, which have been widely used for electronic kiosks and small mobile devices (Colle and Hiszem

2004; Wobbrock and Myers 2008), are becoming one of the common interfaces for notebook and desktop personal

computers (PCs). While finger touch interface on PCs may provide users with several advantages over traditional data entry

devices such as direct interaction and multi-touch gestures, the touch interface on desktop touchscreens can cause risks for

musculoskeletal problems.

In order to touch and control what is displayed on a touchscreen display, users need to continuously look at the display,

stretch their arms and hands towards the display, and then conduct various touch gestures on the touchscreen display. When

the display is positioned upright at or near the user’s eye height for comfortable viewing (Seghers, Jochem, and Spaepen

2003; Turville et al. 1998), touchscreen users may experience physical discomfort and fatigue on the shoulder area due to

frequent floating arm (unsupported) postures. To the contrary, if the touchscreen is positioned more horizontally at or near

elbow height for more comfortable data entry and touch gestures, users may experience neck discomfort due to a continuous

look-down posture to look at what to touch and what is displayed (Shin and Zhu 2011).

Findings in previous research indicate that use of desktop touchscreens can produce greater body discomfort and

physical loads compared to the use of traditional PCs with external data entry devices (Shin and Zhu 2011). This study is

limited, however, in that it did not consider user’s handedness as a main factor. Unlike computer mouse, desktop

touchscreen interface allows users to interact with targets on the display more freely without any physical medium to hold.

Depending on their handedness, users may interact with the display mainly using the right hand, the left hand or both, and

the hand usage pattern can affect the severity or location of body discomfort.

Previously, differences in hand usage patterns, task performance and body discomfort development between computer

users of different handedness have been reported in research with computer mouse (Hoffmann, Chang, and Yim 1997;

Peters and Ivanoff 1999). However, no study has yet investigated the same for the desktop touchscreen interface. Therefore,

the current study was conducted to investigate the effects of user handedness on the hand usage pattern (preferred touch

area, preferred hand for touch gestures) and the development of body discomfort while using a 2300 desktop touchscreen

q 2014 Taylor & Francis

A part of these results were reported previously in the proceedings of the 2013 Annual Meeting of the Human Factors and ErgonomicsSociety (Kang and Shin 2013).

*Corresponding author. Email: [email protected]

Ergonomics, 2014

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display. Participants were recruited from three handedness groups (left-handed, ambidextrous, right-handed), and their

hand movements and subjective discomfort ratings were quantitatively evaluated.

2. Methods

2.1 Participants

Twenty-one participants who had no physical difficulties in conducting touch gestures using both hands were recruited and

participated in this laboratory experiment. They were classified into three handedness groups (left-handed, ambidextrous,

right-handed) after completing the Edinburgh Handedness Inventory (Oldfield 1971). Seven participants who scored below

240 were grouped into the left-handed, seven who scored between 240 and 40 were grouped into the ambidextrous, and

the rest seven who scored above 40 were grouped into the right-handed (Table 1). No significant differences in height and

weight were found between the three handedness groups ( p . 0.05). Prior to participation, each participant provided

informed consent on a protocol approved by the institutional review board.

2.2 Data collection

Data collection was conducted in an isolated laboratory with a fully adjustable computer workstation. The workstation

consisted of a 2300 multi-touch display (IPS236V, LG Electronics, Korea) mounted on an articulated monitor arm, a desktop

PC running on Microsoft Windows 8, an external keyboard on top of a height adjustable table and an adjustable office chair

without armrests (Figure 1). Armrests were removed to avoid any confounding effects of armrest position on upper

extremity movements and physical stress (Zhu and Shin 2012). Participants were allowed to rest their forearms or hands on

the table surface or on the external keyboard.

Each participant performed web-browsing in three consecutive 10-minute sessions. The web-browsing task was

conducted using a web browser and two newspaper applications of the Microsoft Windows 8. The three applications were

specifically chosen to entail typical touch gestures such as vertical and horizontal scroll, pinch and stretch, tap, press and

hold. During the web-browsing task, the participant was monitored and verbally instructed to conduct at least one touch

gesture in every 30 seconds and switch applications every 3minutes, to keep the attention of the participant and to make

consistent task conditions between participants. The external keyboard was used only when typing web addresses or

keywords. Prior to data collection, the participant was instructed and trained for touch gestures and task protocols, and given

a practice period of at least 5minutes for self-practice.

Before the beginning of the first 10-minute session, the participant was allowed to make adjustments on chair height,

table height and display position (height, distance, tilt angle) for their own comfort, and rated physical discomfort of the

neck, shoulders, wrists and fingers using 10-cm visual analogue scales. Then, the participant began web-browsing and

continued it for 30minutes with a short pause every 10minutes (after each 10-minute session). During each pause, the

participant rated body discomfort again and then was allowed to make further adjustments on the computer workstation, if

desired. The interval between consecutive sessions was kept for less than 30 seconds. During the task, hand movements and

the viewable area of the display were videotaped for 2minutes with a 2-minute interval in each 10-minute session

(2–4minutes, 6–8minutes; 12–14minutes; 16–18minutes; 22–24minutes; 26–28minutes) using a digital video

camcorder. Simultaneously with the video recording of hand movements, head and display positions were recorded using a

three-dimensional motion capture system.

2.3 Data analysis

Discomfort ratings that were collected after each session of web-browsing were subtracted by the initial discomfort rating

(time ¼ 0minute) to compute increments or decrements in subjective discomfort over the duration of web-browsing. The

amounts of changes in the discomfort ratings were then compared between handedness groups and between sessions.

Statistical analyses were conducted by a two-way multivariate analysis of variance (MANOVA) with a Wilks’ lambda

Table 1. Participant information (mean, standard deviation).

# Handedness inventory score Age (years) Height (m) Weight (kg)

All 21 2 1.2 20.2 (1.8) 1.645 (0.076) 59.1 (9.3)Left-handed 7 2 70.0 20.9 (1.9) 1.616 (0.078) 60.3 (11.2)Ambidextrous 7 2 16.4 19.4 (1.1) 1.652 (0.084) 56.2 (8.2)Right-handed 7 82.9 20.3 (2.2) 1.666 (0.069) 60.8 (8.9)

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significance criterion of p , 0.05 to identify any significant main or interaction effects of the web-browsing duration and

handedness, and then by a univariate analysis of variance (ANOVA) on individual dependent variables. Tukey’s post-hoc

analysis was performed for dependent variables that were found to be significantly affected by main factors.

To understand hand usage pattern while conducting touch gestures, participant’s preference for touching hand and

preference for touch area were examined using the video recording of hand movements. The number of touch gestures made

in each of nine different areas of the display (3 rows and 3 columns) was counted for each handedness group (Figure 2).

Other gestures than tap and scroll were not counted, and consecutive gestures for scrolling multiple pages at once were

counted as a single scroll gesture. Preference for the use of either the left or the right hand for conducting touch gestures was

then quantified for the entire touch area of the display by computing the relative frequency (percentage) of left hand gestures

for each gesture type within each handedness group. Effects of handedness and task duration were tested on the percentage

of the left hand gesture by repeated measures two-way ANOVA with a significance criterion of p , 0.05. Bilateral

difference in the frequency was evaluated within each handedness group by a paired t-test. Preference for touch area within

Figure 1. Computer workstation.

Figure 2. Nine touch areas within the display.

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the display was evaluated by computing the percentage of touch gestures made in each of the nine different areas of the

display. Percentage values were compared between the nine areas and between handedness groups by repeated measures

two-way ANOVA. Tukey’s post-hoc analysis was conducted for pairwise comparisons.

In addition to the two sets of main dependent variables of interest, position of the touchscreen display relative to

participant’s eyes was measured for each session to evaluate how handedness and task duration might influence the user-

preferred position of the display and how it could affect body discomfort development. Reflective markers were attached to

participant’s head (lateral sides of both eyes and on the glabella) and the display, and their three-dimensional coordinates

were tracked by eight cameras (OptiTrack System, Naturepoint, OR, USA). Then, a distance between participant’s eyes and

the centre of display, and an angle between horizontal and a line that connected the two points were measured. They were

defined as viewing distance and viewing angle, respectively.

3. Results

3.1 Subjective body discomfort ratings

MANOVA found significant main and interaction effects of handedness and task duration. Subsequent two-factor ANOVA

was conducted on each body discomfort variable (Table 2). All discomfort ratings, except for the left finger discomfort,

increased over time, and the increments became statistically significant after 20 or 30minutes of web-browsing (Figure 3).

Between handedness groups, ambidextrous participants reported significantly less neck discomfort increments than the

other two groups. Increments in the left wrist discomfort were significantly less for ambidextrous participants than for the

left-handed, while increments in the right wrist discomfort of ambidextrous participants were significantly less than that of

the right-handed.

3.2 Touching hand preference

ANOVA found significant effects of handedness on the hand preference for tap and scroll gestures (Table 3). No significant

effect of duration was found. Post-hoc Tukey’s test showed that the usage percentage of the right hand was significantly

greater for right-handed participants than for the other two groups. Ambidextrous and left-handed groups used both hands

more evenly than the right-handed, and no statistical difference was found between the left-handed and ambidextrous

groups in the usage percentage values for both gesture types. In the comparison between left and right hand gestures within

each handedness group, it was found that ambidextrous participants used both hands equally, while right-handed and left-

handed participants used their dominant hand more often than the non-dominant hand, except for tap gestures by left-

handed participants (Table 3).

3.3 Touch area preference

Touch area preference was significantly different between the nine areas ( p , 0.05) for all handedness groups. No

significant handedness group effect or interaction effect was found. In general, participants tapped the middle column areas

more often than the left or right side areas. More than 50% of tap gestures were made in the middle column areas (51.9–

57.3%), and the highest tap frequency was observed in the middle-middle area (area 22) for all handedness groups

(Figure 4). For scroll gestures, participants touched the bottom row areas more often than the top row areas. More than 60%

of scroll gestures were made in the bottom row areas (60.3–63.7%), and the highest frequency of scroll gesture was found in

the middle-bottom area (area 32) for all handedness groups.

Table 2. Statistical analysis results for discomfort ratings (p-values).

Shoulder Wrist Fingers

Neck Left Right Left Right Left Right

Handedness , .001 0.342 0.068 , .001 0.008 0.092 0.142Duration , .001 0.003 0.001 , .001 0.019 0.110 0.044Interaction 0.048 0.868 0.792 0.003 0.724 0.539 0.896

Note: Repeated measures two-way ANOVA.

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3.4 Preferred position of the touchscreen display

Participants positioned the display 0.456 m away from their eyes with a viewing angle of 27.68 below their eye height, in

average (Table 4). No significant effect of duration was found on either display position variables. Significant effect of

handedness was found on the viewing angle only ( p ¼ 0.046). Tukey’s post-hoc comparison showed that the right-handed

participants placed the display lower, making significantly greater viewing angle than that of ambidextrous participants.

Figure 3. Increments in subjective discomfort ratings by handedness groups (mean and one standard deviation) (L Sh.: left shoulder;R Sh.: right shoulder).

Table 3. Preference for touching hand (mean and standard deviation).

Tap

p-valuesa (b/w hands)

Scroll

p-valuesa (b/w hands)Left hand Right hand Left hand Right hand

Left-handed 58.3 (26.7) 41.7 (26.7) 0.211 65.5 (15.1) 34.5 (15.1) 0.001Ambidextrous 53.4 (32.6) 46.6 (32.6) 0.631 57.1 (24.7) 42.9 (24.7) 0.219Right-handed 22.0 (27.7) 78.0 (27.7) , 0.001 28.3 (23.4) 71.7 (23.4) 0.001p-valuesb (b/w groups) , 0.001 , 0.001 , 0.001 , 0.001

aPaired t-test; bRepeated measures two-way ANOVA.

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4. Discussion

In this study, hand usage pattern and body discomfort development associated with the use of a desktop touchscreen were

evaluated from 21 participants of different handedness. Participants reported a gradual increase in body discomfort during

the use of the desktop touchscreen display, and the increments in body discomfort varied between handedness groups for

some body parts. Study results also show that right-handed participants had stronger laterality than the left-handed, and

ambidextrous participants used both hands more evenly than other participants, suggesting associations between hand usage

pattern and body discomfort development.

The left-handed participants showed differences in touching hand preference between the two gesture types, and it could

be attributable to differences in performance requirements between tap gestures and scroll gestures. Tap gestures typically

require precise aiming and reaching movements towards specific target items within the display. Left-handed participants,

who are known to be less strongly lateralised than the right-handed in aiming performance (Annett et al. 1979; Borod,

Caron, and Koff 1984; Peters and Durding 1979), might have conducted tap gestures with a hand near to each target for

faster operation with less arm movement. To the contrary, scroll gestures, which were conducted to scroll up/down or left/

right with single finger swiping on any location within the display, did not require as much aiming performance as tap

gestures might do. Therefore, the left-handed and right-handed participants might have conducted scroll gestures mostly

with their dominant hand, while the ambidextrous participants used both hands more equally.

Scroll gestures on a desktop touchscreen display are generally made by wrist flexion-extension and radial-ulnar

deviation to turn web pages during web-browsing. The frequent use of the dominant hand for scroll gestures might have

resulted in the significant difference in the wrist joint discomfort between handedness groups. In our post-hoc analysis, it

was found that participants conducted scroll gestures more often than tap gestures, and it is believed that the frequent

rotation of the wrist joint for scroll gestures might lead to the more pronounced difference in the wrist discomfort ratings

between handedness groups compared to that of other body parts. While the left-handed and the right-handed, who mainly

used dominant hand, reported larger increments in discomfort of the dominant wrist, the ambidextrous participants reported

less overall wrist discomfort thanks to their balanced use of both hands.

Ambidextrous participants also reported significantly less neck discomfort than others, and it could be due to their

smaller viewing angle compared to that of other participants. Increase in viewing angle is known to result in the greater neck

flexion of PC display users (Delleman and Berndsen 2002), and maintaining a looking down posture has often been

attributable to the development of neck discomfort of PC users (Kothiyal and Bjornerem 2009; Seghers, Jochem, and

Spaepen 2003). Although the difference in mean viewing angle between the ambidextrous and other participants was less

than 58, it might have caused less head forward flexion of the ambidextrous participants and contributed to their less neck

Figure 4. Touch area preference and Tukey’s post-hoc comparison results. Cells with different letters indicate significant differences.

Table 4. Preferred position of the touchscreen display (mean and standard deviation).

Handedness Viewing distance (m) Viewing angle (deg)

Left-handed 0.446 (0.051) 27.2 (6.8)Ambidextrous 0.463 (0.055) 25.3 (6.6)Right-handed 0.456 (0.051) 30.3 (6.7)

p ¼ 0.327 p ¼ 0.046

Note: Repeated measures two-way ANOVA.

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discomfort. It is not known, however, why ambidextrous participants placed the display higher than the others, and it needs

further evaluation in future research.

Findings of the current study suggest that body discomfort of desktop touchscreen display users could be moderated by

user-interface (UI) design and user training. Results of touch area preference hint the possibility of improving user comfort

and satisfaction by improving UI of operating systems or applications for desktop touchscreens. From the analysis of touch

area preference, it was found that participants preferred the lower areas for scroll gestures and the middle column areas for

tap gestures. Since scroll gestures can be made at any location within the display, participants might have chosen the lower

areas for their own comfort and productivity. Different from scroll gestures, tap gestures need to be made to specific target

items within the display. The strong preference for the middle column areas for tap gestures might be attributable to the

centred layout of typical websites and/or participant’s preference for positioning the main contents in the centre area within

the display by zoom or scroll gestures. It may not be desirable to place main contents in the lower area of the display because

of resultant looking-down posture and greater neck flexion, but other operating items such as menus and toolbars can be

located in the lower areas within the display to reduce frequency and/or duration of elevated arms.

In addition, study results also suggest that users may be able to reduce cumulative body discomfort by alternating hands

between the dominant and the non-dominant, as previously recommended to computer mouse users (Ackland and Hendrie

2005; Peters and Ivanoff 1999). Although not statistically significant, left-handed and ambidextrous participants reported

less increments in shoulder discomfort than the right-handed, and it might be attributable to their more balanced use of both

hands compared to the right-handed when conducting touch gestures. A longer task duration or a larger sample size could

have shown significant differences between handedness groups.

It should be noted that the potential benefits of UI design improvements or alternating hands for conducting touch

gestures may not be sufficient to eliminate or lower the concerns for musculoskeletal problems to the level of traditional PC

interfaces (mouse, keyboard). Additional ergonomics interventions such as the use of elevated armrests need to be

employed together to address the health concerns associated with the use of desktop touchscreens. It should also be noted

that the research questions of the current study need to be further examined with additional research to produce more

generalisable results and to make more structured and direct recommendations. First, future research should include more

detail and quantitative comparisons of aiming and touch performance (speed, accuracy) between handedness groups to

develop practical design guidelines and recommendations. Second, future study should include larger sample size per

handedness group to make more generalisable and reliable recommendations. Third, heavier task scenarios need to be tested

to examine improvements in touch proficiency over prolonged or repetitive uses, and to understand how the skill

improvements influence hand usage pattern and body discomfort development over time.

Acknowledgements

This study was supported by the Office Ergonomics Research Committee (OERC).

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