Computer Ergonomics - Avoiding MSD and RSI

7/28/2019 Computer Ergonomics - Avoiding MSD and RSI

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Computer Ergonomics - Avoiding MSD and RSI

Introduction

In 2001, the Occupational Safety and Health Administration (OSHA) of the United States hadscheduled a new safety regulation for computer workers to go into effect in the Fall of that year.This regulation addressed the risks of physical injuries associated with computer usage (see

"What Is MSD/RSI?"). The regulation required employers to provide employees with

information and training on how to avoid such injuries - specifically, OSHA directed employers

to provide all employees with a printed booklet and classroom instruction on risks, symptoms,and prevention.

A client company gave Matthew Harris the task of preparing a printed booklet and trainingcurricula in compliance with the new OSHA regulation. This article is a revised version of the

safety booklet prepared in accordance with the OSHA requirements.

What Is MSD & RSI?

Musculo-Skeletal Disorder(MSD) is a blanket term for illnesses and diseases of the muscles,

tendons, skeleton, and connective tissues, such as tendonitis.Repetitive Stress Injury (RSI) is atype of MSD, and refers to injuries to the muscles, bones, or connective tissues caused by

repetitive motions. Carpal Tunnel Syndrome is an example of a common RSI. MSD and RSI

injuries can take many forms, and can affect any part of the human structure; typically in thehands, shoulders, neck, spine, knees, or ankles.

What Causes MSD/RSI?

Repetitive Stress Injury (RSI) occurs when a person performs the same motion over and over;

especially if the motion is performed intensely over a long period of time and involves awkwardbody positions and/or application of force. Long periods of typing, improper workstation setup,

incorrect work habits and/or problems in your personal health may be linked to MSD or RSI.

When you work muscles intensely, the individual cells in your muscles produce waste products

faster than your circulatory system can carry them away. The cell waste products, calledfatigue

poisons, build up in the muscle and other body tissues, and cause swelling. In turn, the swelling

reduces circulation, and causes a further build-up of fatigue poisons, resulting in further swellingwhich reduces circulation even more, and so on in a vicious cycle. Swelling in muscles and

connective tissues often puts pressure on nerve pathways, resulting in temporary or permanent

damage to the nerves.

As an example, a common type of RSI is Carpal Tunnel Syndrome. The tendons that move yourfingers pass through small tunnels in the carpal bones at the back of your hands (hence the name

carpal tunnel syndrome). When your hands are overworked, the tissues around the carpal tendons

swell, and the tendons become too large to move freely through their bone tunnels; the tendons
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then scrape against the bone and pinch the nerves that share the carpal tunnel with the tendons.

The result is a painful, crippling loss of mobility and control of the hands.

Other types of MSD have similar causes, mostly related to a lack of circulation. For example,

constant vibration can drive blood away from the part of the body experiencing the vibration,resulting in tissue and nerve damage.

Some types of MSD, however, are caused by a lackof motion. The joints of the human body,like the moving parts of machinery, must be lubricated for the joint to move freely. Although the

human body produces its own internal lubrication for the skeleton's joints, movement of the joint

is necessary for the lubrication to be spread over the bearing surfaces. If you don't move the

various joints in your body through their full range of motion, the available range of motiontends to become less.

Who gets MSD/RSI?

Young or old, anyone in any occupation can get MSD or RSI. Although we currently most hear

about RSI related to computer work, you can get RSI or other MSD from any sort of work, andeven from your hobby and recreational activities.

For example, RSI has been a problem afflicting assembly-line workers for over a century now.

Piano players have been known to get Carpal Tunnel Syndrome, and there is an MSD known as

"bassoon finger" caused by the fact that bassoon players support most of the weight of their

instrument with one finger of one hand when playing. Motorcyclists are subject to an MSDknown as "tingle-finger" which is caused by vibration in the handlebarsthe vibration drives

blood out of the fingers, resulting in nerve and tissue damage in the hands. In recent years,

teenagers are being diagnosed with a malady known as "texter's thumb", caused by using one'sthumbs for too much typing.

Carpenters, engineers, painters, sculptors, drafters, programmers, designers, students anyoneat all can be at risk for MSD/RSI.

MSD/RSI Symptoms & Warning Signs

The symptoms and warning signs of MSD/RSI usually appear in the hands, wrists, arms,shoulders, neck, or back. Symptoms include:

Pain Numbness Tingling Throbbing Weakness Swelling

Burning Soreness Aching Cramping Stiffness


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You may feel such symptoms when typing, using a mouse, drawing, or any number of otheractivities.

You may also experience these symptoms when you're not engaged in the activity responsible

for the injury, such as at night.

If you experience any of the symptoms listed, or any other pain or discomfort you think is related

to an RSI, you should promptly consult a doctor.

Additional Risk Factors For MSD/RSI

Your ability to avoid MSD/RSI while working or pursuing recreational activities can be affected

by your general state of health. Some factors that have been shown to increase an individual's

risk for MSD/RSI are listed below.

Inflammatory disease, such as arthritis Diabetes Excessive weight Hypertension Stress Smoking Conditions affecting hormone levels, such as pregnancy or menopause Advancing age General poor physical condition

In the preceding list, notice that most of the complicating factors are related to conditions that

may impede blood circulation. Use of tobacco products, for example, puts nicotine in yoursystem. Nicotine is a vasoconstrictor drug, and reduces blood circulation in the extremities,hence increasing the risk of RSI such as Carpal Tunnel Syndrome.

The remainder of this article describes proper computer workstation setup, posture, and work

habits to help you avoid MSD/RSI.


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Preventing MSD/RSI

he basic techniques for avoiding MSD and RSI are to use good ergonomics in your workstation,

and to engage in healthful work habits and lifestyle.

Ergonomics is the study of adapting work or working conditions to suit the worker. This sectiondescribes basic ergonomic posture, briefly describes correct ergonomics for working at a desk

without a computer, and then describes the correct ergonomics for a computer workstation in

detail.

Note The fundamental item you'll need to achieve correct ergonomics at your workstation is a height-

adjustable chair. Ideally, your chair should also have a tilt-adjustable seat (the seat of an office chair is

sometimes called the pan), and the ability to adjust the distance of the back from the seat. If your

workstation desk does not have a height-adjustable top, you'll probably need a footrest of some kind.

Basic Ergonomic Work Postures

The basic elements of good ergonomic posture involve three points:

Keep wrists and neck straight; don't bend them up, down, or to the side. Avoid pressure from edges of tables and chairs (even blunt or rounded edges) against the wrists,

arms, back, or legs.

Keep shoulders, arms, and hands relaxed.Working At Your Desk

When working at your desk (using pencil and paper, as opposed to using your computer), youshould sit upright, with your weight slightly forward. Keep your work close to you, and your

forearms flat on the table-top. Your hips should be slightly higher than your knees, without

putting pressure against the backs of your thighs from the edge of your chair's seat. If your chairhas a tilt-adjustable seat, it should be tilted slightly forward.

Computer Workstations

When working at your computer, you should sit upright in a relaxed posture, with your weight

slightly to the rear. Avoid either slouching forward, or leaning too far back. Your knees shouldbe slightly higher than your hips, especially avoiding pressure on the backs of your thighs from

the edge of your chair's seat. If your chair has a tilt-adjustable seat, it should be tilted slightly

back.


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Ergonomics At Your Computer

Figure 1

Correct Posture for Computer Work

This section explains correct posture while working at your computer, and describes how to

correctly determine the height for your chair, desk or table top, and monitor display. This section

also describes how to correctly position your mouse and keyboard.

Computer Work Posture

Keep your shoulders relaxed, with your forearms and wrists parallel to the floor. Adjust your

table and chair heights so that your forearms are parallel to the floor, with your wrists straight

(refer toFigure 1). You should be able to maintain the correct arm position and place both feet

flat on the floor. If you cannot place both feet flat on the floor without pressure on the backs ofyour thighs, use a footrest to raise your knees. Sit against the back of your chair, and position

your chair's backrest so that your lower back is firmly supported.

Most computer workstation furniture has height-adjustable table tops and monitor shelves.

Preferably, you should adjust your chair for correct leg height, then adjust the height of yourtable top for the correct arm position. If your table is not height-adjustable, adjust your chair

height to obtain the correct arm position, and then use a footrest to obtain the correct leg

position.
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Monitor Height & Position

Position your display monitor directly in front of you at a comfortable viewing distance;

typically about 18 to 24 inches. If you use a document holder, position it at the same level and

near the display monitor.

Keeping your neck straight is an important part of computer ergonomics. The height of your

monitor tends to control your neck position. If your monitor is too high, you'll end up tilting yourhead backwards, resulting in neck strain.

There are two basic rules you can apply to determine the correct monitor height for you:

The top of the monitor's display should be at eye-level when your neck is held in anupright position.

If you can't use the rule above (as happens with very large monitors), a secondary rule isthat the center of the monitor's display area should be at shoulder height, enabling you tosee the entire display area without tilting your head backwards.

Note If you wear multi-focal corrective lenses (bi-focal, tri-focal) you may find yourself tilting your

head back to bring the monitor into the appropriate focal range. If this is the case for you, lower your

monitor so that you don't need to tip your head back.

Tip If you wear multi-focal glasses, consider getting a pair of "task glasses" to wear when using your

computer task glasses are made for your near-vision correction, eliminating any need to tilt or turn

your head to focus on different areas of your monitor. Task glasses can save you a lot of neck and eye-

strain.

Positioning & Using The Keyboard

Figure 2Proper Keyboard Wrist Position

Your keyboard should be directly in front of you so that you can reach it easily with your elbowsremaining in a relaxed position at your side. Remember to keep your shoulders, arms, wrists, and

hands relaxed as you type, with your upper arms hanging freely at your sides. When typing, keep


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your wrists straight (refer toFigure 2). Do not splay or arch your wrists up or down (Figure 3), or

to the sides (Figure 4).

Avoid resting your arms or elbows on the edge of the table. Use a wrist pad to support your

wrists and/or cushion the edge of a table, but don't let the weight of your arms rest on the pad.

If you have a chair with arms, don't rest your elbows or forearms on the arms of the chair while

working. Doing so has two negative effects: first, resting your elbows or forearms on the arms ofthe chair tends to lock your arms in place. With your arms immobilized, you are more likely to

splay or arch your wrists and/or experience shoulder pain. Secondly, resting your elbows or

forearms on the arms of the chair is another source of point-pressure which may affect

circulation and/or put direct pressure on nerve bundles.

It is best to use a chair without arms for computer typing and mouse work.

Figure 3Don't Do This: Wrists Flexed Up Or Down

Figure 4Don't Do This: Wrists Flexed In Or Out
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Positioning & Using The Mouse

Position the mouse at the same level as the keyboard, and within easy reach. Like the keyboard,you should use the mouse with your forearm parallel to the floor, and your wrist straight (refer to

Figure 5). Make sure that the thickness of the mouse pad does not raise the mouse higher than

your elbow, forcing you to bend your wrist.

Figure 5Proper Mouse Wrist Position

Use your whole arm to move the mouse. Hold the mouse with a relaxed hand; avoid gripping the

mouse tightly.

Many people experience strain when using a mouse in activities that involve a lot of dragging or

double-clicks. Keep in mind that MS Windows can be configured so that items usually selected

with a mouse click are selected when the mouse pointer is moved over the item, and that items

activated with a double-click can then be activated with a single click. Also, a multi-buttonprogrammable mouse can help eliminate strain in the hands. Typically, you configure one or

more of the mouse buttons to provide a double-click, without the user actually having to double-

click.

If you perform many mouse-drag operations, you may find it easier and more comfortable to use

an alternate pointing device, such as a trackball. A trackball avoids stress on the finger tendonsby using the fingers to perform delicate maneuvers and the thumb for clicks. Because the thumb

tends to be much stronger than the fingers, a trackball may alleviate fatigue associated with using

a mouse.

The same basic recommendations for using a mouse apply when using trackball or touchpad

pointing deviceskeep your wrists straight and relaxed, parallel to the floor.
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Notes For Laptop Users

All of the guidelines here apply to laptop users. Laptop users need to be especially careful of

wrist position. Using the laptop in your lap often results in wrists arched back (not a good thing,

ergonomically). Many on-the-go locations, such as a cafe table, will be too high, resulting inwrists arched down. In 2010, many news sources began reporting on a condition known as

"laptop thigh" or "toasted skin syndrome", a rash and discoloration of the skin caused by holdinga hot laptop on one's thighs.

Arm & Hand Motion

Use natural, comfortable motions to avoid strain. Keep your mouse and keyboard within easy

reach. Also keep frequently used work materials within easy reach; frequent over-extension toreach reference books or other work materials may result in injury.

Use these motion guidelines when working at the computer:

When typing, keep forearms and wrists level and parallel to the floor. Keep your elbows in a relaxed position near your body, but don't press them tightly against your

body.

When using the keyboard, mouse, or other input device, keep your wrists in a natural, straightposition. Avoid bending, arching, or angling your wrists.

If you use a palm rest, use it only briefly for resting. Do not use a palm rest, or rest your handson the table, while you are typing.

Keep your thumbs and fingers in a relaxed, natural position. Use the minimum amount of force needed to push down keys or mouse buttons. Avoid banging

on the keys or pressing mouse buttons with more than the minimum force required.

Preventing Eye Strain

Eye strain is not an MSD or RSI. Eye strain and fatigue are, however, a common experience forpeople who spend long periods looking at a monitor displaypreventing eye strain is an

important topic when discussing how to improve your well-being while working or playing at

your computer.

Follow these general guidelines to help reduce eye strain and fatigue:

Eliminate (or reduce) reflections and glare from the monitor screen (seeReducing Reflections &Glare). Use the brightness and contrast controls on the display to improve character and image quality.

A too-bright display can be a source of eye strain.

Use the customizing features of your operating system and video drivers to increase the size atwhich text and symbols are drawn on your screen.

Take frequent breaks and rest your eyes, be sure to focus on objects at varying distances. Keep your glasses, contact lenses, and the display clean.
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If you use a glare filter, clean it according to the instructions. Have your eyes examined regularly by a vision care specialist; out-of-date corrective lenses can

cause a lot of discomfort.

Consider having glasses made that are specifically suited for working with the computer display.The remainder of this section discusses two common eye strain problems:dry eyes, and

reflections/glarefrom the monitor screen.

Dry Eyes

When you look at a computer monitor screen, the rate at which you blink your eyes (blink-rate)

goes down.

This can cause a great deal of discomfort during long periods of computer use. With a lowered

blink-rate, your eyeballs are moistened less frequently, and are likely to begin feeling irritated.

This drying effect may be especially noticeable to persons wearing contact lenses.

To alleviate this extra drying, try massaging the outer corners of your eyes to help lubricatethem, and take frequent breaks from looking at your monitor. If you wear contact lenses, you can

use an eye lubricant approved by your vision-care specialist.

Reducing Reflections & Glare

To reduce or eliminate the most common causes of eye strain - reflection and glare - you need topay attention to both how you place your equipment and how you light your work area.

Basically, any strong light source behind you will cause reflections and reflected glare on yourmonitor screen. A strong light source in front of you will cause glare, and make it difficult to see

the image on your monitor.

You need to position your monitor and/or alter the room lighting to avoid glare or bright

reflections on the monitor screen.

In general, placing your screen at right angles to strong light sources (such as a window) will

eliminate or reduce reflections from that light source. (This means the side of the monitorenclosure is facing the bright light source.)

If an overhead light source is causing reflection/glare, you can often use the monitor's tiltingfeature to eliminate the problem - tilt the monitor forward or back to change its angle in relationto the offending light source and eliminate the glare.

Other tips to help arrange the lighting, or arrange the monitor in relation to lighting:

Position the display between the rows of overhead lights to avoid glare. Combine general and task lighting, but avoid bright light sources in your field of vision.
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Use indirect lighting to avoid bright spots on the display.

Tip

Focusing on objects at varying distances can help reduce eye fatigue. Periodically look up fromyour monitor and focus on something 20 or more feet away from you. If you don't have a line of sight to

something 20 feet away, use a mirror to increase the focal length - for example, if you look at something

15 feet behind you reflected in a mirror 5 feet in front of you, your eye has to focus as if the viewed

object is 20 feet (15 + 5) away.

Healthful Work Habits

The arrangement of furniture, equipment, and lighting are not the only factors that determine your riskfor MSD/RSI. Your work habits are also very important. This section recommends good work habits to

help reduce your risk of MSD/RSI.

First and foremost, vary your activities. Take some time to analyze the types of tasks you perform. Break

up your routine and try to vary your tasks so that you do not end up sitting in one position or performing

the same activities with your hands for several hours at a time. Staying too long in one position, or

repeating the same motion many times, causes discomfort and injury. Do something different with your

hands and arms for a while. For example, if you typically do several hours of data-entry each day, see if

you can intersperse other tasks with your data-entry so that you do not end up typing non-stop for

several hours at a time.

Note People have different levels of physical tolerance for working intensively over long periods.

Monitor your personal tolerance levels, and avoid regularly exceeding them. If any of theadditional risk

factors for MSD/RSIapply to you, it is especially important for you to know your personal limits.

Note If it hurts, stop! MSD/RSI can be a lifetime crippling disorder. Absolutely the worst thing you

can do is "work through the pain." If you have any of thesymptoms of MSD/RSI, and altering your

workstation/work-habits doesn't help, see a doctor.

If you must work at your computer for prolonged periods, make sure you take periodic breaks.

Get up, stretch, and walk around at least twice every hour, if only for a minute or two. Frequent,short breaks are probably of greater benefit than fewer, longer breaks - especially in light of

recent research regarding the detrimental effects of sitting still for as little as one hour.

Other suggestions for work habits that can reduce your risk of MSD/RSI:

Work in a relaxed, natural position. Avoid awkward or strained postures.
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Alter your sitting posture frequently to reduce muscle fatigue; stand up and stretchfrequently.

Avoid long periods of repetitive motions (such as typing). Improve circulation in your extremities through exercise, massage, warmth (such as

warming your hands by washing them). Remember to use the customizable features of MS Windows and/or your mouse to help

you work with less strain.

Safety & Comfort Checklist (Summary)

Use this checklist as a reminder when adjusting your workstation ergonomics to increase your comfort

at work or play, and to reduce your risk for MSD/RSI.

Keep your forearms and wrists parallel with the floor when you type or use the mouse.Do not angle your forearms up or down.

Type with your wrists in a natural, straight position. Avoid bending, arching, or anglingyour wrists.

Ensure your chair height allows you to maintain the proper arm and hand position. Be sure your chair supports your lower back. Rest your feet flat on the floor or on a foot rest. Use the minimum amount of force needed to push down keys and mouse buttons. Take periodic breaks when working at your computer for prolonged periods. Arrange your monitor for comfortable viewingyou should be able to see the entire

display without tilting your head back.

Vary your tasks during the day to avoid sitting in one position or performing repetitivemotions for several hours without interruption.

Avoid reflections and glare on the monitor display by careful placement of the monitor,and by controlling room lighting.

Have your eyes examined regularly by a vision care specialist. Stretch and exercise several times a day.

Wishing you happy and healthful computing!

Note Only you can determine the best workstation arrangement for the way you work. Your

choices, however, should be based on an understanding that working intensely, or for a long timein uncomfortable or unnatural positions, can pose risks.

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Computer Ergonomics - Avoiding MSD and RSI

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