In an article published in Work: A Journal of Prevention, Assessment, and Rehabilitation, on January 15, 2012, Harvard School of Public Health researchers have begun quantifying the ways in which a person’s posture, and also the design of the tablet and its case, affects comfort.
The prestigious New England Journal of Medicine actually ran a letter from a physician noting the unfortunate side effect of children reading more, and for longer periods, than they ever had in their lives. One paediatrician, Dr.Howard J. Bennett, finally realized that all three of the headache-ridden children he saw in one week were obsessively reading the newly released Harry Potter and the Order of the Phoenix, a book that runs to over a quarter of a million words. Two of his patients refused to stop reading at their current rate, instead opting for a prescription to dull the pain. He noted that, “In all cases, the pain resolved one to two days after the patient had finished the book.”
Falaki et al. (2010)
conducted by Jinghong Xiong and Satoshi Muraki vol57, ISS.6, 2014
TABLETS AND SMART PHONES
HOW TO MANAGE THEM ERGONOMICALLY
PREVENT REPETITIVE STRESS INJURIES.
Rise of the Computer
• Increase in computer
• Various aches and pains
we now know as
• The computer-now
slowly got hand held
• Metamorphosed into a
tablet, a smart phone
Hand Held Devices
• Significant rise in use
compared to PC
• Combined use PC+
• Increased risk of
• We look at various tablets and smart phone
dimensions and its use.
• We explore the postures users assume while
using these devices.
• We evaluate the possibilities of WMSDs
arising from prolonged use of such postures
• Aim to provide certain guidelines for risk
• Tablet sizes across the
world vary from 5inch
to 11inches (case size)
Operating a Tablet
• Tablets are used by people mainly to watch
movies, play games.
• Recently they are increasingly being used for
more and more times for long meetings etc.
• In an article published in Work: A Journal of Prevention,
Assessment, and Rehabilitation, on January 15, 2012,
Harvard School of Public Health researchers have
begun quantifying the ways in which a person’s
posture, and also the design of the tablet and its case,
• Fifteen experienced tablet users were in a lab to
complete a set of simulated tasks on an Apple iPad2
and a Motorola Xoom.
• All of the volunteers were adults under 40.
• Each tablet had a proprietary case that could be
adjusted to prop up the tablet at an angle.
• Users were situated in four postures:
– Lap-Hand (tablet held on lap)
– Lap-Case (tablet placed on lap in case at its lower
angle setting—15 degrees for the iPad and 45
degrees for the Xoom)
– Table-Case (tablet placed on table with its case at
its lower angle setting)
– Table-Movie (tablet placed on table in case at its
higher angle setting—73 degrees for the iPad and
63 degrees for the Xoom).
• While users browsed the Internet, responded to email,
played games, and watched a movie, their head and neck
posture and gaze angle were measured using an infrared
three-dimensional motion analysis system.
• The researchers found that study participants’ heads and
necks were in more flexed positions while using the tablets
than those typical of desktop or notebook computer users.
• Working for long periods of time with the head slumped
forward and the neck flexed can result in neck pain.
• Users held their heads in the most neutral positions when
sitting in the Table-Movie configuration.
• Tablets are used as a portable device and hence
lack a proper operating environment.
• It is subject to awkward postures, awkward
viewing angles and improper lighting conditions.
• Different people use tablets of different
dimensions and weights.
• These factors promote improper ergonomic
postures and over time these could lead to
various repetitive stress injuries.
WMSD risk areas-Tablet
• Neck-Cervical radiculopathy
• Shoulder-iPad shoulder
• Wrist and hands-iPad hands/carpal tunnel
• Hands- de Quervain syndrome, a painful affliction
that involves the tendons that move the thumb.
• Lower back-pain due to improper posture and
• Hogwarts headache
• Use an external keyboard and mouse, that makes
the setup look more like a desktop.
• Users should “move more; vary positions as much
• Use cases that let them keep the device propped
on a table at about a 60- to 70- degree angle to
prevent neck strain.
• Set the font size larger so that one can read
material in the appropriate neutral posture with
back and neck in a straight vertical line.
• Ensure that chairs are adjustable, so users can use
tablets with their backs and arms supported.
• Ensure adjustable window blinds and overhead lights
with glare preventing baffles are installed in meeting
rooms and breakout areas where people are likely to
• Equip meeting rooms with accessories (e.g. external
keyboards) that can be used by anyone.
• Provide covers to all users to support typing.
• Provide any other external aids (stands, docking
stations, external keyboards, etc.) when required or
requested for users who use tablets at their desks.
Evolution of the mobile phone
• Initial mobile phone in
• It evolved rapidly in the
• From black and white to
HD colour devices
• Mini Computer
Multitasking with Smart Phone
• Smart phones are increasingly being used for
texting, emailing and browsing the web, with less
time spent on “the phone”.
• The posture that is assumed while performing
these activities, i.e. using thumbs to type while
hunched over a tiny keyboard, is very stressful.
• If performed repeatedly over extended periods
of time, it increases the risk of musculoskeletal
Operating a Smart Phone
• Use varies from low of 30mins-high of 500mins
• Daily average-10mins-200mins/day
• Used mainly as a communication tools (e.g.
email, text messages, instant messaging) this
accounted for 44% and 49%
• Although phones are mainly operated by holding
in one hand with the thumbs, it does require
stability via muscles at the wrist, elbow, shoulder
Operation Analysis of Smart Phone
• A study investigated the relationship between the thumb
muscle activity and thumb operating tasks in smartphone.
Touch screen with one hand posture.
• The study revealed that demand on first dorsal
interosseous (FDI) muscle increases when the thumb taps
small buttons and in flexion –extension orientation.
• But the demand on abductor pollicis longus increases in
adduction and abduction orientation.
• The study reveals that muscle effort among thumb muscles
on a touch screen smartphone varies according to the task,
and suggests that the use of small touch buttons should be
minimised for better thumb performance.
WMSD risk areas-Smart Phone
• With smart phones, the thumb is the main part used
for most operations.
• Dequervains syndrome is a common diagnosis or the
now outdated blackberry thumb
• CMC joint arthritis.
• Some other WMSDs may also include, Text Neck,
shooting pains down your neck and arm, as well as
numbness or tingling in your fingers and hand.
• Carpal tunnel syndrome. CTS (although there isn’t
much evidence to suggest smart phone use can cause
CTS, it can surely aggravate any existing condition.
• Draft briefer messages.
• Use word recognition to reduce keystrokes
• Keep the wrist in a neutral (straight) posture.
• Hold the phone in a position that allows for a more upright
neck and upper back posture.
• Keep moving, change your position often and take frequent
• Do more on your computer.
• Texting with two thumbs, with the back and forearms
supported, were less likely to be “symptomatic” than those
who texted with one thumb, or sat with the neck and back
Sizing up your smart phone
Smaller than 4.5 inches Medium 4.5-5.5 inches Larger than 5.5
• Tablets are portable devices. The risk of rsi (repetitive stress injury)
with extended use is very real and clinics around the world are
already diagnosing and treating such cases.
• Practically speaking-It is very difficult to adapt an ergonomically
correct position, whenever someone uses and tablet or a mobile
• There will however be certain scenarios when a correct
ergonomical position or a near correct ergonomical position can be
• Users must therefore be trained in correct ergonomic use of such
devices to enable then to correctly use them whenever possible.
• In situation which do demand certain deviations from the
‘ergonomic positions’ users should be educated in concepts of ‘rest
breaks’, ‘stretches’ etc.
• Surely, ergonomists somewhere must be toiling away to ensure that the
next generation of smartphones is likely to address these issues, and we
are anxious to see how the user will view the screen with the head
balanced over the shoulders, and enter text with the hands and wrists in a
• Already, some devices provide options to allow a variety of postures to be
used to control the devices (i.e. keyboard AND touch screen)
• In the next smartphones… how will the interface with the hand become
• How will the devices project a display into a space where it can be seen
with neutral neck and shoulders?
• Maybe people will learn a new syntax to reduce how much they have to
• Will language recognition progress to allow us to enter sentences without
typing out full words? Is a stylus better than a keyboard??
• An Ergonomic evaluation of the potential impact of touch screen tablets on office
workers. Katarzyna Marta Stawarz .Faculty of Brain Sciences, University College
• An ergonomics study of thumb movements on smartphone touch screen Jinghong
Xiong, Satoshi Muraki Ergonomics Vol. 57, Iss. 6, 2014