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July 2000


Dec. 2005


Jan. 2007


Ergonomics associated with the

Use of a Touch Screen Desktop PC

Gwanseob Shin, Ph.D. & Xinhui Zhu

Department of Industrial and Systems Engineering

The State University of New York at Buffalo

Sponsored by:


Background


Background


Background


Background


Research Objectives & Questions

Development of a workstation guideline for touch screen PC

Is there a comfortable workstation setting for the touch

screen

Will users experience more (or less) discomfort with

the touch screen


Study Structure – Independent Variables

Condition #1

Keyboard

• Mouse

• No touch control

Condition #2

Keyboard

• Touch control

Condition #3

• Touch keyboard

• Touch control

23.5” touch screen PC running on Windows 7

Within-subject design

5 min. rest between conditions


Study Structure – Dependent Variables

User-preferred position of the display and the keyboard

Viewing angle

Tilt angle

V. Typing

distance

Keyboard

-elbow

Tracking of reflective markers

Y

H. Typing distance

Seat

height

origin X

Keyboard

height

from floor

Display

height


Study Structure – Dependent Variables

Myoelectric activity (EMG) of neck and shoulder muscles

Neck extensors

Upper

trapezius


Methods – Participants

Age (yrs) Height (cm) Weight (kg)

Female (13) Mean 26.0 162.3 57.8

SD 3.2 4.3 8.1

Male (11) Mean 23.5 173.7 74.5

SD 3.7 5.5 11.2

Handedness

Right 21

Left 3

Counter-balanced

123

132

213

231

312

321


Methods – Task

Simple computer use task

•Visual search/scan

•Scrolling

•Right & left clicks

•Typing

15 minutes

Adjust workstation every 3

minutes for his/her comfort


Methods – Data Processing & Analysis

EMG

Band-pass filtered (10-500Hz)

Fully rectified

Linear envelope (3Hz)

Normalized

Statistical analyses

Repeated measures ANOVA

Tukey’s post-hoc test

Significance criterion of p


Tilt angle (deg)

Results – Display position

*p


Display height (m)

Viewing angle (deg)

Results – Display position

50

40

30

*

*

*

20

10

0

kb + mo kb + touch touch only

0.9

0.8

*

*

0.7

0.6

0.5

kb + mo kb + touch touch only


Results – Preferred display position

Keyboard + mouse Keyboard + touch Touch only


V. keyboard distance (m)

H. keyboard distance (m)

Results – Keyboard position

0.7

0.6

0.5

0.4

0.3

0.2

0.1

0.0

* *

kb + mo kb + touch touch only

0.0

-0.1

kb + mo kb + touch touch only

-0.2

-0.3

-0.4

-0.5

* *

*


Right elbow height (m)

Left elbow height (m)

Results – Elbow height (above elbow rest)

0.12

0.10

0.08

0.06

0.04

0.02

0.00

-0.02

*

* *

kb + mo kb + touch touch only

0.00

-0.02

-0.04

-0.06

-0.08

-0.10

-0.12

kb + mo kb + touch touch only


% maximum EMG

% maximum EMG

Results

– Muscle activity (EMG)

*p


% maximum EMG

% maximum EMG

Discussion

Objectives

To determine user-preferred setting

To assess biomechanical loads

0.20

0.15

0.10

Neck muscles

kb + mo kb + touch touch only

0.05

0.00

Left

Right

0.25

0.20

Shoulder muscles

kb + mo kb + touch touch only

0.15

0.10

0.05

0.00

Left

Right


Discussion

Preferred position of the Touch screen

(touch only)

Display height

Viewing distance

Tilt angle

Glare

Eye strain

Viewing angle

Head/neck bending

Neck muscle activity

Neck fatigue,

discomfort

Eye convergence

Visual fatigue


Discussion

Preferred position of the Touch screen

(touch only)

Display height

Tilt angle

Glare

Eye strain

Viewing angle

Head/neck bending

Neck muscle activity

Neck

fatigue,

discomfort

External keyboard

Shoulder elevation

Shoulder muscle

activity

Viewing

distance

Eye

convergence

Shoulder fatigue,

discomfort

Visual fatigue


% maximum EMG

Discussion

Touch screen with an external keyboard

0.25

0.20

0.15

kb + mo kb + touch touch only

0.400

ebow-rest gap.r-y

0.10

0.350

0.300

0.05

0.250

0.00

Left

Right

0.200

0.150

0.100

0.050

0.000


Discussion – Design considerations

Advantages of touch screen interface

Usability

Direct control and feedback

Size of the touch screen

Thumb Hand Arm

Physical capacity: Range of motion, Fatigue, etc.

Visibility

Visual acuity

Amount/type of information

Viewing distance

Workstation

Elbow support, hand support

External devices (e.g. keyboard)

Training


Thank You!

Questions

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