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CHAPTER 56OFFICE ERGONOMICS*

Marvin Dainoff, Wayne Maynard, and Michelle RobertsonLiberty Mutual Research Institute of SafetyHopkinton, Massachusetts

Johan Hviid AndersenDepartment of Occupational MedicineHerning Hospital, Herning, Denmark

1 CONCEPTUAL OVERVIEW 1551

1.1 Introduction 1551

1.2 An Ecological Approach to Ergonomics 1551

1.3 Foundations 1551

1.4 Elements of an Ecological Frameworkfor Ergonomics 1552

2 EPIDEMIOLOGICAL EVIDENCEFOR CARPAL TUNNEL SYNDROMEAND UPPER EXTREMITYMUSCULOSKELETAL DISORDERSAMONG COMPUTER USERS 1554

2.1 Introduction 1554

2.2 Carpal Tunnel Syndrome 1555

2.3 Upper Extremity MusculoskeletalDisorders 1555

3 ERGONOMICS PROGRAMS FOR OFFICEENVIRONMENTS 1557

3.1 Employer Responsibilities 1557

3.2 Training 1557

3.3 Employee Involvement 1557

3.4 Injury and Hazard Surveillance 1557

3.5 Evaluation and Management of WMSDCases 1559

3.6 Job Analysis 1559

3.7 Job Design and Intervention 1560

4 OFFICE FURNITURE DESIGN 1560

4.1 Seating and Viewing Considerations 1560

4.2 Work Surface and Seated ClearanceConsiderations 1561

5 GETTING A GOOD ERGONOMICMATCH BETWEEN OPERATORAND WORKSPACE 1562

5.1 Talk to Your Employees 1562

5.2 Making Height Adjustments 1562

5.3 Direct Measurement Techniques 1562

5.4 Operator Measurements (Dainoffand Dainoff, 1986) 1562

5.5 Adjust the Chair Height 1563

5.6 Position the Keyboard and Mouse 1563

5.7 Position the Monitor 1563

5.8 Dual-Monitor Guidelines 1563

5.9 Laptop Computers 1563

5.10 Positioning the Laptop 1564

5.11 Other Considerations 1564

6 EYE STRAIN AND FATIGUE 1564

6.1 CVS: Symptoms, Causes, and Controls 1564

6.2 Control Options for Eye Muscle Strainand Fatigue 1565

7 MOBILE WORKERS: MANAGINGSAFETY OF TELECOMMUTERS 1565

7.1 Tips for Working at Home 1566

7.2 Using a Laptop Computer at Home 1567

7.3 Consider Your Environment 1568

7.4 Making a Good Ergonomic Fit 1568

8 INTERVENTION STRATEGIES 1568

9 CONCLUDING REFLECTIONS 1569

9.1 More Complete Characterizationof Exposure 1570

9.2 Focus on Quality and Performance 1570

REFERENCES 1570

* The opinions in this chapter are those of the authors and donot represent the positions of Liberty Mutual Group or HerningHospitals.

1550 Handbook of Human Factors and Ergonomics, Fourth Edition Gavriel SalvendyCopyright © 2012 John Wiley & Sons, Inc.

OFFICE ERGONOMICS 1551

1 CONCEPTUAL OVERVIEW

1.1 IntroductionThe purpose of this chapter is to present an overviewof ergonomic issues in the office workplace. However,in determining the scope of this material, it is necessaryto consider a fundamental question: What is an office?In the modern electronic workplace, the answer is notstraightforward. A traditional (Compact Edition of theOxford English Dictionary , 1971) definition states thatan office is “a place for the transaction of private orpublic business.” With the profusion of portable com-puters and hand-held devices currently available, almostany location can fit that definition: an airport waitingroom, a kitchen table, an automobile, even a parkbench. Nevertheless, this chapter must focus on evidence-based findings, and the bulk of such research has beenconducted in traditional offices. Therefore, we will focuson workplaces whose primary purpose is some aspect ofinformation processing and transformation, where somesort of computer equipment is employed, and whoseoccupants are expected to remain in place for extendedperiods of time (i.e., several hours). On the other hand, thegeneral principles discussed here can be usefully appliedto more temporary venues (e.g., setting up a temporaryworkspace with a laptop and modem in a hotel room).Of particular interest is the increasingly frequent caseof telework in which individual employees are—eithervoluntarily or involuntarily—expected to set up theirprimary workplace at home.

The chapter cannot hope to be comprehensive. Asearch of the terms “office ergonomics” in Google Scho-lar resulted in 72,000 hits. Even allowing for overlap,a comprehensive literature review would likely resultin all of the allocated space for this chapter being com-posed of citations. Nevertheless, it is the intent of theauthors that at least the major issues will be introducedand discussed with sufficient citations to enable thereader to explore these issues in depth.

The contribution of individual authors can be specif-ically identified. In Section 2, Johan Andersen presentsa systematic review of the epidemiological literaturelinking carpel tunnel syndrome and upper extremity dis-orders among computer users. In Sections 3 through 7Wayne Maynard relies on consensus standards [Busi-ness and Institutional Furniture Manufacturers Associa-tion (BIFMA), 2002; Human Factors and ErgonomicsSociety (HFES), 2007], the draft report of the Z365committee of the National Safety Council (AccreditedStandards Committee, 2002), and many years of prac-tical experience to summarize ergonomic recommenda-tions for office design from a practitioner’s perspective.In Section 8, Michelle Robertson considers the evidencefor effective interventions. Finally, Marvin Dainoff pro-vides a conceptual framework (Sections 1 and 9) andis responsible for overall organization and integration.The authors do not speak with one voice and disagree-ments will appear. We regard this as a strength of thechapter. As Root-Bernstein (1989) argues, “it is notconsensus for which we must strive, but the elabora-tion of as many adequate descriptions of nature as wecan imagine—in short the sort of complementarist viewespoused by Bohr” (p. 375).

1.2 An Ecological Approach to Ergonomics

This overview is based on previous work (Dainoff andMark, 2001; Dainoff, 2005, 2008).

Galison (1997) has provided an intriguing study ofthe development of the field of microphysics, from thenineteenth century cloud chamber to the factorylike lab-oratories of the present day at places like the EuropeanOrganization for Nuclear Research (CERN), Stanford,and Berkeley. His particular focus is on the way inwhich the development of laboratory apparatus trans-formed the social/organizational structure of micro-physics from individual investigators working alone orin small groups with total control and understanding oftheir apparatus to industrial-style organizations requir-ing collaboration among many professionals. In orderfor this collaboration to have occurred, Galison invokesthe concept of “trading zones” (1997, p.46). Derivedfrom the field of linguistics, trading zones refer to sim-plified languages (creoles, pidgins) that arise when adja-cent cultures require a mutually understandable meansof communication in order to transact business. Gali-son’s insight has important implications for the field ofergonomics.

Just in the area of ergonomics of chairs and furniture,the applicable research involves individuals from a num-ber of academic specialties, including biomechanics,epidemiology, economics, industrial engineering, indus-trial medicine, industrial design, muscle physiology,multivariate statistics, psychology of human perfor-mance, psychophysics, organizational design, orthope-dics, and optometry. What is required is a trading zone,a conceptual framework within which specialists in onearea can communicate with specialists in another.

1.3 Foundations

Two books were written at the end of the 1940s, whichtogether should have changed the face of psychology.Both of these books offered naturalistic approaches tobasic psychological processes which, prior to that time,had been treated in highly abstract ways, torn out oftheir functional contexts (Reed and Bril, 1996, p. 242).

The first of these books was J. J. Gibson’s Perceptionof the Visual World (Gibson, 1950); the second, whichwas suppressed for political reasons, was Bernstein’s OnDexterity and Its Development . The volume was finallypublished (Bernstein, 1996), and it remained for thosewho followed and elaborated the Gibsonian positionto incorporate Bernstein’s insights into the ecologicalposition. See, for example, Turvey et al. (1978).

Gibson’s ecological approach to psychology, as out-lined in his last book (Gibson, 1979), provides part of thefoundational basis for ecological ergonomics. Gibsonrejected the prevailing view of psychology as the studyof an individual organism, in which environmental con-text is simplified or ignored. Instead, he argued that theindividual and environment are so tightly and recipro-cally coupled that they cannot be studied independentlyof one another. Thus, to understand the simple case of aperson walking across a field, a detailed physical analy-sis of the terrain is required—including characterizationof the projected optical flow patterns across the retina

1552 SELECTED APPLICATIONS IN HUMAN FACTORS AND ERGONOMICS

associated with movement in a given direction. Becausethis approach takes into account the interacting aspectsof both person and environment, Gibson called it an“ecological” approach. Gibson’s arguments are similarto the systems-versus-psychological distinction made byMeister (1989) and, in fact, Gibson himself saw simi-larities between his view and systems theory (Vicente,1999).

While Gibson argued for the importance of viewingperception within the functional context of behavior in theenvironment, Bernstein presented a parallel argument forviewing actions within their functional/adaptive contexts.What he called “dexterity” is a capacity of solving motorcontrol problems under dynamically changing parameters(Reed and Bril, 1996). Hence, movement science cannotstudy movements as abstract patterns without takinginto account functional demands of task constraints,environmental constraints, and (changing) constraintswithin the individuals themselves (Newell, 1996).

1.4 Elements of an Ecological Frameworkfor Ergonomics

The core of this approach rests on the parallelism betweenbasic concepts of ergonomics and ecological psychology.Ergonomics can be characterized as the fit between thehuman being and those things (tools, workplaces, envi-ronments) with which he or she interacts (Dainoff andDainoff, 1986). At the same time, ecological psychol-ogy provides a theoretical foundation which allows us torelate the physical attributes of people and their envi-ronments with behavioral acts required to function inthat environment (Gibson, 1979). Therefore, the factthat both ecological psychology and ergonomics focuson the mutual relationship between person and environ-ments leads us to propose an ecological framework forergonomics.

The starting point for analysis is a single individual(or “actor”) interacting with his or her environment.Two conceptual building blocks form the core of thisanalysis: affordances and perception–action cycles.

The first component of the ecological framework isthe concept of affordance. Affordances are attributes ofthe environment of an individual (or “actor”) definedwith respect to the action capabilities of that individ-ual (Dainoff and Mark, 2001; Gibson, 1979). Insofar asthe fundamental definition of ergonomics can be con-strued in terms of the fit between individual and envi-ronment (Dainoff and Dainoff, 1986; see above), theconcept of affordance, as developed within the theoreti-cal framework of ecological psychology, provides a sys-tematic approach to understanding and critical analysisof person–environment complementarity. Thus, compo-nents of an ergonomic chair are affordances for alter-nating between different seated work postures, but onlyfor a particular set of users. The chair is not usableas designed for a two-year-old child who is too small,an extremely obese adult who is too large, or a per-son with muscle impairment who is unable to adjust thecontrols. The chair is not functionally usable by the per-son who does fall in the above categories but does notunderstand either how to adjust the controls or why suchadjustments might be useful.

The concept of affordance is particularly relevantto ergonomic aspects of design, since it requires thedesigner to explicitly take into account how physicalobjects relate to the action capabilities of users.Action capabilities, in turn, are determined by certainclasses of constraints: personal, environmental, and task(Newell, 1996). Personal constraints refer to individualvariability, including body dimensions (anthropometry),biodynamics (body strength, mass, flexibility), andrelevant psychological factors (perceptual, cognitive,motivational). Environmental constraints include bothsize and shape of objects and surfaces as well as theirphysical properties relevant to the action.

The second component of the ecological frameworkfor ergonomics is the perception–action cycle. Any in-tegrated behavior pattern (task) can be decomposed intoa series of steps in which perceived information aboutthe possibility of action is followed by the action itself,which, in turn, reveals new information about potentialactions, and so on. For example, information is extractedfrom the home page of a website indicating the presenceof a clickable button. Hand and finger muscles move themouse to the location of the button and click. The effectof the click is to act on the environment—a new Webpage appears. The new page has additional information,some of which is extracted (perceived) and the cyclecontinues. (See Figure 1.)

Perception–action cycles are defined by certainclasses of constraints, which can be classified into fourgroups. Task constraints reflect the functional require-ments of a task. This includes individual task demands.A second class of constraints consists of surround-ing social and organizational factors. Workspace con-straints reflect the layout of components within theworkspace (e.g., display, input/out device, furniture)as well as relevant environmental constraints (lighting,air quality, temperature and humidity, gravity). Indi-vidual constraints reflect both physical (anthropometricand physiological) and psychological (cognitive, moti-vational, emotional) attributes of the actor.

The action components of perception–action cyclestake place within a three-dimensional postural envelope.Within the postural envelope, the operator must reach,lift, and manipulate, while parts of his or her body areor are not supported.

The perception–action cycle is the theoretical con-ception which links Gibson’s concept of affordancewith Bernstein’s concept of skill as the coordinationof multiple degrees of freedom. It is the informationabout affordances which, when perceived, initiates theperception–action cycle by revealing the capabilitiesfor action within the environment. At the same time,the existence of multiple affordances within the sys-tem requires a degree of coordination through selectionand timing of appropriate task-relevant actions associatedwith appropriate affordances. When this coordination canbe achieved under changing environmental constraints,the user has achieved what Bernstein called “dexterity”(Bernstein, 1996). Consequently, we argue that the per-ception –action cycle should be the fundamental unit ofanalysis of work systems and, therefore, a basic tool forergonomics.


Perception

Action

Individual Task

EnvironmentalOrganizational

Figure 1 Perception–action cycle defined by constraints.

1.4.1 Application of the FrameworkThe preceding conceptual framework can be used as apractical tool, a kind of lens with which the remaininginformation in this chapter may be viewed.

Let us consider in detail the example of a user seatedat a fully adjustable computer workstation while writingan article for a book chapter. The adjustability of theheight and angle of the seat, angle of the backrest,height and angle of the keyboard support, height andangle of the monitor, as well as the scalable font size ofthe word-processing program are all affordances whichallow this particular person to achieve a comfortableworking posture. Each of these affordances referto physical properties of the workstation defined interms of corresponding attributes (action capabilities)of the actor’s anthropometry, motor control ability,and understanding of operation and coordination of thecontrol mechanisms. These affordances are defined inexplicit detail in Section 4. Thus, in a real sense, theproducts of design are affordances.

A critical point here, and one that is often misun-derstood, is that the physical attributes described aboveare only considered affordances if they are perceived assuch by the actor. That is, a chair may have a heightadjustment lever, but if the actor does not know that itexists, knows that it exists but does not know its loca-tion, knows its location but not how it operates, or knowshow it operates but does not have the physical capabilityto operate it, the chair does not have an affordance forheight adjustability.

If, on the other hand, the actor is fully aware ofthe functionality of each of the components above, theybecome affordances enabling the individual to adapt tothe complexity of the workstation in that he or shecan achieve comfortable/efficient working posture. Moreprecisely, this awareness can allow the execution ofmultiple nested perception–action cycles.

Consider the detailed task requirements involved increating text in the process of composing a book chapter.This involves periods of rapid keyboard operationinterspersed with periods of reflection and pondering.Therefore, one set of perception–action cycles involvesthe linkage between actions of the fingers on the keys and

corresponding reading of the text on the screen. Here thefingers and eyes are playing a primary role whereas theremaining bodily structures (head, neck, arms, shoulders,trunk) are in a more passive supporting role. Whatwe call efficient/comfortable working posture is a setof perception–action cycles which adjust the relativelocations of these limbs into orientations which allow theprimary keying–reading cycle to be easily performed.[Note: The term “comfort” here is a convenient labelfor a hypothetical underlying physiological principle ofefficiency or least effort. (See, e.g., Nubar and Contini,1961.) ]

In a well-designed office environment, efficient/comfortable posture is afforded by the adjustabilitymechanisms in that the seat and backrest can be adjustedso that that the trunk can be inclined backward withthe feet flat on the floor and the lower back supported.The keyboard support is adjusted so that the handsare flat and forearms parallel to the floor. The headis erect and the monitor is within a field of view 30◦below the horizontal. The backward-inclined workingposture places the eyes over 100 cm from the displayscreen, but this is compensated for by increasing thefont size of the displayed characters. These criteria forcomfortable posture are contained in many standards andguidelines [e.g., American National Standards Institute(ANSI)–HFES 100-2007: U.S National Standard forHuman Factors Engineering of Computer Workstations(HFES, 2007)] and are reviewed later in Section 4.

It is useful to examine in the detail the perception–action cycle for just one of these adjustments—seatheight. It is assumed that the actor is fully informed aboutthe functionality of the particular chair he or she is usingwhich has a height adjustment lever (HAL) below the seatsurface on the right side. Table 1 depicts the four stagesof the perception–action cycle required to operate thislever and raise the level of the seat to the desired height.This entails locating the lever, pulling it upward while atthe same time elevating the buttocks, and allowing theseat surface to move upward to a desired height. In thiscase, both the HAL and seat surface can be consideredaffordances.


Table 1 Perception–Action Cycle for Height Adjustment of Ergonomic Chair

Continue

Tactile/visualpickup: seatheight not yetcorrect

Elbow heightlower than worksurface

Seat surfacemoves upwardto new positionof buttocks

Grasp and pullHAL: rotatethighs andbuttocks upward

Tactile pickupthat HAL isgraspable

HAL is inoperatingposition(graspable)

Hand movesto HAL

Arm extensionplus grasp

Tactile/visualpickup of HALlocation

Height adjustmentlever (HAL) rightside below seat

Action ActivationPerceptionInformation

What is the desired height? In this case, the goal is toraise the trunk so that the elbows are approximately levelwith the keyboard. At the same time, the legs should bestraight and feet flat on the floor. Depending on theindividual anthropometry of the actor, this goal maynot be achievable without additional perception–actioncycles, such as adjusting the height of the keyboardsupport surface.

A completely different set of perception–action cyclesis brought into play if the task requirements change.Assume that a section of the chapter has been finishedand printed on paper copy. The actor’s preference is toplace the paper document on a copy holder adjacentto the display screen for further editing. Hence a newadaptation in working posture to these changed demandsis necessary. Because the small font size on the paperdocument is no longer visible while the seat back isinclined rearward, the seat back must be adjusted to amore upright position.

In Bernstein’s terms, a certain degree of dexterity(coordination of multiple degrees of freedom) is requiredto utilize the adaptive potential of a modern ergonomicoffice to achieve the desired goal of efficient/comfortableworking posture for multiple task demands. Thesedegrees of freedom are manifest as individual furnitureadjustment mechanisms and major joints of the body.Depending on the particular equipment supplied, adjust-ment mechanisms can include seatpan angle, seatpanheight, backrest angle, backrest height, backrest tension,work surface height, monitor height, and monitor angle.Major joints include wrist, elbow, shoulder, neck, thigh,knee, and ankle.

While the motor control mechanisms for coordinat-ing postural degrees of freedom is the subject of consid-erable research activity within the ecological psychologycommunity (see, e.g., Latash and Turvey, 1996), for thepurposes of this chapter, it is sufficient to reiterate thepoint made earlier that the actor must understand bothhow to adjust the controls and why such adjustmentsmight be useful. Simply put, user training must be anessential component of office ergonomics.

Therefore, to return to where we started, fit (Dainoffand Dainoff, 1986) is achieved when the appropriateconstraints and affordances are available so as to allowadaptive perception–action cycles to move the actor intoa three-dimensional postural envelope (comfort zone)within which task activities can be carried out with aminimum of physical effort (see, e.g., Newell, 1996).

2 EPIDEMIOLOGICAL EVIDENCEFOR CARPAL TUNNEL SYNDROMEAND UPPER EXTREMITY MUSCULOSKELETALDISORDERS AMONG COMPUTER USERS

2.1 IntroductionMusculoskeletal disorders of the neck and upper limb(UEMSDs) and carpal tunnel syndrome (CTS) have beenlinked to keyboard and visual display terminal (VDT)use since the beginning of the 1970s. Early reportson occupational cramps and muscle pain appeared inAustralia (Ferguson, 1971) and Japan (Maeda, 1977)after use of electric keyboards or among accountingmachine operators. Later, an apparent epidemic occurredin Australia in the mid-1980s, where so-called repetitionstrain injuries (RSIs) were frequently reported amongcomputer users. The epidemic disappeared, and thebackground and causes of the epidemic have beendiscussed ever since. Historically, there have beensimilar examples of outbreaks of pain and cramps—forexample, writer’s cramp or telegraphers’ cramp (Dembe,1996)—often coinciding with the introduction of newtechnology into the society. Arguments on causes toexplain the outbreaks have ranged from specific physicalexposures at the workplace to cultural beliefs and societalexpectations (Lucire, 2003). In Europe and the UnitedStates, the first concerns on health effects of VDTs werepotential adverse effects on reproduction, which has beenrefuted by large epidemiological studies.

The majority of UEMSDs are characterized byrecurrent episodes of pain and consequent disability,varying in severity and impact. Most of the episodesare self-limiting and subside within days or weeks, while


some end up with long-lasting chronic problems. Riskfactors from physical, psychological, and social domainshave been identified, but the relative contribution ofthe various risk factors to the onset and aggravationof UEMSDs is less known. As a result, controversiesstill exist regarding the degree of work-relatedness ofUEMSDs (Silverstein et al., 1996).

The last decades, since the anecdotal stories in the1970s and the early reviews, have been characterizedby a steady increase in the number of published studieson computer work and UEMSDs, The studies generallyfall into one of two categories: either experimentalstudies trying to identify a possible pathophysiologyof computer-related disorders or intervention studiesand epidemiological studies focusing on the associationbetween workplace risk factors and musculoskeletaloutcomes.

The pathophysiological studies have produced alarge number of hypothetical injury mechanisms rang-ing from a systematic overload of low-threshold motorunits (the “Cinderella” hypothesis) to intracellularCa2+ accumulation, impaired blood flow, reperfusioninjury, blood vessel nociceptor interaction, myofascialforce transmission, intramuscular shear forces, triggerpoints, and aggravated heat shock response. There isa certain degree of overlap between the hypotheses,but in spite of intensive research the empirical datato support a unifying hypothesis or identify a specificinjury mechanism has been limited. It is assumedthat pain results from muscle tissue damage due toprolonged low-force muscle activity with few breaksand little variation. However, muscle activity measuredby electromyography seems to be slightly higher duringrest breaks and noncomputer office work than duringcomputer work. In a study by Richter et al. (2009), thedivision between computer activity and noncomputeractivity was based on electronic activity registrationwith different cut-offs. These observations may be seenas support for few, if any, biologically plausible effectsof mouse work on UEMSDs.

The pathophysiological or mechanistic studies arenot included in this chapter. Instead, the scope is tosummarize the knowledge and synthesize the evidencegained from the large number of risk factor studies,including prospective studies, which have been pub-lished since 2000. Although several systematic reviewson computer work and UEMSDs and CTS have beenpublished in recent years in an attempt to provide thiskind of information, the conclusions in the reviews areoften in discord and the heterogeneity has created a sit-uation of confusion rather than of clarity.

2.2 Carpal Tunnel Syndrome

Carpal tunnel syndrome is a compression neuropathyof the median nerve as it passes through the carpaltunnel. It is regarded as the most frequent compressionneuropathy. Based on both clinical symptoms andnerve conduction tests (NCTs), overall prevalences of3.0–5.8% among women and 0.6–2.1% among menhave been found in general population samples (Atroshiet al., 1999). CTS is generally believed to be causedby increased pressure in the carpal tunnel. It is widelyaccepted that exposure to hand–arm vibrations and

exposure to a combination of repetitive hand use andhand force may be causally related to CTS. In recentyears, with the expanding use of computers, it has beena matter of concern if computer use could be a riskfactor for the development of CTS. Three recent reviewsof high quality concluded that there is insufficientepidemiological evidence that computer work causesCTS (Palmer et al., 2007; Thomsen et al., 2008; VanRijn et al., 2009). Table 2 summarizes the aims andmain conclusions from the three reviews.

2.3 Upper Extremity MusculoskeletalDisordersUpper extremity musculoskeletal disorders cover a widerange of complaints from the neck, shoulder, elbow,forearm, and wrist/hand. Umbrella terms such as repeti-tion strain injuries (RSIs), occupational cervicobrachialdisorders (OCDs), and cumulative trauma disorders(CTDs) have often been used in the literature, but termslike these assume that the proposed mechanisms orexposure must be avoided. It is fairly consistent fromthe literature that distal arm pain and, to a lesser extent,neck–shoulder pain are associated with intensive use ofthe keyboard and the mouse, and the conclusions fromseveral reviews (Gerr et al., 2004, 2006; Griffiths et al.,2007; IJmker et al., 2007; Village et al., 2005; Waerstedet al., 2010; Wahlstrom, 2005) are shown in Table 2.The reviews are based on a total of 80 original studies.

The association is much more uncertain when itcomes to computer use and more prolonged or chronicpain and clinical entities such as shoulder tendonitis,lateral and medial epicondylitis, forearm disorders, orwrist tendonitis. Researchers recently performed a criticalreview of the epidemiological evidence for a possiblecausal relationship between different aspects of computerwork, including keyboard and mouse use, and neckand upper extremity musculoskeletal disorders diagnosedwith a physical examination (Wahlstrom, 2005). As canbe seen in Table 2, they found limited epidemiologicalevidence for an association between aspects of computerwork and the clinical diagnoses. There is a tendencyfor recent reviews to be more critical than earlierreviews, even though newer and prospective studieshave been included in the reviews. In epidemiologicalstudies it is usually found that more and better studiesprovide stronger evidence for a causal relation if suchexists in the real world. The current level of findingsis in contradiction with a causal relation betweenaspects of computer use and clinical verified UEMSDs.Nevertheless, this should be carefully interpreted. Withthe very widespread use of computers in professionalwork life and in leisure activities, even a small increasein risk could have profound importance and, based onour current knowledge, we cannot discount such smallrisks. Over the last 25 years we have witnessed somebig changes in the office environment. The physicalwork environment has changed and, maybe of moreimportance, the psychosocial and work organizationalcircumstances have changed toward increase in officeworker flexibility, more precarious work, and incessantorganizational changes. Loss of worker autonomy, lackof predictability and meaning, and appreciation bysupervisors or peers are probably of more importancein today’s office work than biomechanical loads.


Table 2 Aims and Main Conclusions from Reviews on Risk Factors for CTS and UEMSDs among Computer Users

Carpal Tunnel Syndrome

Palmer et al., 2007 Aim: To assess occupational risk factors for CTSConclusion: The balance of evidence on keyboard and computer work does not indicate an

important association with CTS.

Thomsen et al., 2008 Aim: To examine evidence for an association between computer work and CTSConclusion: There is insufficient epidemiological evidence that computer work causes CTS.

Van Rijn et al., 2009 Aim: A quantitative assessment of exposure–response relationships between work-relatedphysical and psychosocial factors and the occurrence of CTS in occupational populations

Conclusion: The contradictory findings for computer use and the development of CTS are inagreement with the conclusion of a recent review (Thomsen et al., 2008).

Upper Extremity Musculoskeletal Disorders

Gerr et al., 2004 Aim: The epidemiological evidence examining associations between UEMSDs and computer useposture and keyboard use intensity (hours of computer use per day or per week).

Conclusion: Daily or weekly hours of computer use is more consistently associated with hand andarm MSDs than with neck and shoulder MSDs.

Wahlstrom, 2005 Aim: To give a summary of the knowledge regarding ergonomics, musculoskeletal disorders, andcomputer work and to present a model that could be used in future research.

Conclusion: None. It is hypothesized that perceived muscular tension is an early sign ofmusculoskeletal disorder, which arises as a result of work organizational and psychosocialfactors as well as from physical load and individual factors.

Village et al., 2005 Aim: To evaluate the evidence supporting a causal relationship between computer work andmusculoskeletal symptoms and disorders (MSDs) of the hand, wrist, forearm, and elbow.

Conclusion: There is consistent evidence of a positive relationship across numerous prospectiveand cross-sectional studies with increased risk most pronounced beyond 20 h/week ofcomputer use or with increasing years of computer work. The disorders confirmed withphysical examinations are wrist tendonitis and tenosynovitis, medial and lateral epicondylitis,and DeQuervain’s tenosynovitis. The risk of carpal tunnel syndrome is increased with a use of acomputer, especially with mouse use for more than 20 h/week.

Gerr et al., 2006 Aim: To explore the epidemiological evidence of associations between upper extremitymusculoskeletal symptoms and disorders and keyboard use intensity (hours of computer useper day or per week) and computer use postures

Conclusion: A somewhat consistent finding is an observed association between hours ofcomputer use and adverse hand/arm MSD outcomes and, to a slightly lesser extent, betweenhours of computer use and adverse neck/shoulder outcomes.

The conclusion also points to severe methodological limitations in the literature.

Griffiths et al., 2007 Aim: To draw attention to the potential risks to musculoskeletal health with the computerization ofwork among professional occupational groups.

Conclusion: The risk factors for work-related musculoskeletal symptoms with computer workhave been extensively researched and are generally well established.

IJmker et al., 2007 Aim: To get a more conclusive insight into the relationship between the duration of computer useand the incidence of hand–arm and neck–shoulder symptoms and disorders, a systematicreview of longitudinal studies was performed.

Conclusion: This review showed moderate evidence for an association between the duration ofmouse use and the incidence of hand–arm symptoms. Indications for a dose–response werefound. In addition, the neck–shoulder region seemed less susceptible to exposure to computeruse than the hand–arm region.

Waersted et al., 2010 Aim: To examine the evidence between computer work and neck and upper extremity disorders(except carpal tunnel syndrome).

Conclusion: There is limited epidemiological evidence for an association between aspects ofcomputer work and some of the clinical diagnoses. None of the evidence was considered asmoderate or strong and there is a need for more and better documentation.


3 ERGONOMICS PROGRAMS FOR OFFICEENVIRONMENTS

Ergonomics is the design of jobs to match the capabili-ties and limitations of workers. Jobs designed ergonom-ically result in higher productivity and quality andimproved workplace safety. To achieve such outcomesin ergonomics requires a managed health and safetyprocess that targets the design of tasks, workstations,tools, equipment, and organizations to reduce risk fac-tors that can contribute to injury and disability. Manybelieve the most effective ergonomics program in anoffice environment is one that properly fits an employeeat their computer workstation with the chair, keyboardand mouse, monitor, or display at the correct heightwith proper seated posture. In reality, proper worksta-tion adjustment is but a small component of an officeergonomics process.

The following guidelines, comprising Section 3 ofthis chapter, are adapted from the 2002 final draftof ASC Z365 Management of Work-Related Muscu-loskeletal Disorders (Accredited Standards Committee,2002) and describe the elements of an ergonomics pro-gram and process for managing work-related muscu-loskeletal disorders (WMSDs) to reduce frequency anddisability.

An ergonomics program for WMSDs has the follow-ing components:

• Employer responsibilities• Training• Employee involvement• Injury and hazard surveillance• Evaluation and management of WMSD cases• Job analysis• Job design and intervention

3.1 Employer Responsibilities

Effective implementation of a managed ergonomicsprocess will require establishing priorities for preventionand control activities. The choice of priorities willdepend on the progress made in addressing workplacefactors and on the extent of problems already present inthe workplace. Some will focus first on management ofdiagnosed WMSD cases and evaluation and interventionof the corresponding jobs. Others, in worksites withfew or no WMSD cases or high employee turnover,may move straight to implementing proactive jobsurveys (e.g., employee interviews, checklists) so thatpotential problems associated with particular jobs canbe identified and addressed before new WMSD casesappear.

The level and breadth of training and employeeinvolvement may directly depend on how the programis initiated and progresses over time. As Figure 2 shows,there are three surveillance outcomes that could leadto job analysis. An employer may focus first on theemployee reports and, in doing so, provide the appropriatetraining and employee involvement to accomplish thisgoal. As one moves to surveillance using existing recordsand job surveys, participants may change and so may the

corresponding level and breadth of training and employeeinvolvement.

3.2 TrainingPeriodic training is necessary so that employees andmanagers can facilitate surveillance, job analysis, jobdesign, and medical management. Be sure to providetraining to appropriate management representatives andemployees. Training may include:

• Recognition and reporting of the signs andsymptoms of WMSDs that may be work related

• Record-keeping processes for reporting WMSDs• Whom to contact for further assistance• Roles and responsibilities in the surveillance

procedures• Recognition and management of WMSD risk

factors• Job analysis and design procedures• Proper use, adjustment, and maintenance of

tools, work equipment, and work stations• Job interventions and best-work procedures and

practices for minimizing risk of WMSDs

3.3 Employee Involvement

Give employees the opportunity to participate in theprogram for management of WMSDs. The followingare examples of employee involvement:

• Submitting suggestions or concerns• Participating in discussions related to their

workplace and work methods• Participating in employee surveys• Participating in formal team meetings• Using and operating tools and work equipment

in the prescribed manner• Participating in the design of work, equipment,

and procedures• Participating in the employer’s WMSD problem-

solving process• Participating in WMSD education and training• Notifying the employer of related WMSD symp-

toms and risk factors early

3.4 Injury and Hazard SurveillanceThe results of surveillance are used to determine whenand where job analysis is needed and where ergonomicinterventions may be warranted. Each organization maywant to establish criteria for when a job survey resultor health surveillance data indicate the need for a jobanalysis. This information may be further used to assistin establishing job analysis and intervention prioritiesand assessing the program. Surveillance includes:

1. Initial review of existing records of work-related illnesses and injuries [e.g., OccupationalSafety and Health Administration (OSHA) logand workers’ compensation records] and at thestart of surveillance, periodically thereafter. This


Program management

No

Surveillance

Record review, trends, employee reports

Job analysis

Obvioussolution?

Newor substantially changedtools, equipment or work

processes?

Identify risk factorsand

characteristic properties

Job designor redesign

Risk factorsreduced oreliminated?

Design processends

Job design and intervention

Yes

Yes

Yes

Yes

Yes

Yes

YesYesYes

MSD symptoms?

WMSD risk factors? Baseline

assessmentdone?

Problemjob?

No

No

No

No

Case closed

Workrelated?

No

No

NoNo

Job survey

Ongoingsurveillance

HCPevaluation Recent WMSD

HCP treatmentand follow-up

Symptomsimproved?

MSD management

Employer responsibilities, employee involvement and training

Figure 2 Program for management of WMSD flowchart illustrating program elements. (Adapted from the 2002 final draftof ASC Z365 2002; Accredited Standards Committee, 2002.)

analysis will help determine where WMSDs areoccurring and will help prioritize jobs needingfurther analysis.

2. Employee reports—There are two kinds of em-ployee reports:

a. Employee reports of WMSD symptoms

b. Reports of employee concerns about WMSDrisk factors

3. Job surveys—The aim of job surveys is toidentify specific jobs and processes that may putemployees at risk of developing WMSDs. Jobsurveys are considered a cursory or preliminaryreview of jobs, as compared to a more detailed

job analyses. Job surveys may include any of thefollowing methods:a. Office walkthroughsb. Employee and supervisor interviews/ques-

tionnairesc. Computer workstation design assessment

checklistsd. Team problem-solving approaches

Job surveys can be incorporated into existing pro-grams such as regular safety, health, team problem solv-ing, or quality inspections and can expand their scope toinclude identification of WMSD risk factors. Results ofjob surveys may be applied to similar jobs within oneor more departments or locations:


Perform job surveys when:

• New WMSD cases are reported, to help deter-mine if risk factors exist across similar jobs thatuse similar tasks, equipment, tools, or processes.This might include a sampling of representativejobs.

• Employees report new MSD symptoms.• Employees report WMSD risk factors.• There is an unexplained high rate of turnover

or absenteeism for a specific job. There may bemany reasons for turnover or absenteeism notrelated to WMSDs.

• Surveillance activities are begun as a baselineassessment of job risk factors.

• A job, equipment, or process substantiallychanges to identify risk factors that may resultfrom making these changes.

• New equipment or furniture or work processesare planned, purchased, or installed.

3.5 Evaluation and Management of WMSDCasesEarly assessment or establishing a diagnosis and ini-tiating treatment may limit the severity, improve theeffectiveness of the treatment, and allow for sufficientand timely recovery of the condition. Early identificationof WMSDs can alert the employer to the need for jobanalysis of that employee’s job or the need for furtheranalysis if the job has already been evaluated.

It is recommended that employers:• Examine existing policies, practices, and pro-

grams to ensure that they encourage promptreporting of MSD symptoms or potential WMSDrisk factors without reprisals.

• Once notified of recurrent or persistent MSDsymptoms, facilitate a prompt evaluation of thesymptomatic employee by an appropriate healthcare provider (HCP) consistent with state laws.

• Provide the HCP with a contact who is familiarwith the job tasks.

• Provide HCPs the opportunity to become famil-iar with jobs and job tasks (e.g., site walk-throughs, review of job surveys, analysis reports,detailed job descriptions, job safety analyses,photographs, or videotapes).

• Ensure employee privacy and confidentialityregarding medical conditions identified duringthe assessment, as permitted by law.

In addition, employers should:• Select or recommend HCPs with knowledge,

experience, and training in workplace exposuresand the evaluation and treatment of WMSDs.

• Whenever feasible, modify jobs, redesign thejob, and/or accommodate employees with workrestrictions as determined by a HCP.

Note: Refer to the Americans with Disabilities Actfor guidance relevant to employees with disabilities.

The HCP should:• Evaluate the symptomatic employee.• Seek information and review materials regarding

employee job activities.• Be familiar with the management of WMSD

cases or refer the employee to a HCP who isfamiliar with such management.

Components of the HCP evaluation include:• A medical history (occupational and nonoccupa-

tional) which includes a complete description ofsymptoms.

• A description of work activities as reported bythe employee and the employer.

• A review of exposure information relevant to theclinical findings.

• A physical examination appropriate to the pre-senting symptoms and history.

• An initial assessment or diagnosis and anappropriate treatment plan.

• Work restrictions or work modifications if appro-priate.

• An opinion on the work-relatedness of thedisorder based on professional guidelines [e.g.,A Guide to the Work-Relatedness of Disease(Kusnetz and Hutchinson, 1979)].

Employees with WMSDs should:• Provide input to and follow the treatment plan

recommended by the HCP, including workrestrictions.

The HCP should follow up with symptomatic em-ployees to document symptom improvement or reso-lution or reevaluate the employee who may not haveimproved. The time frame for this follow-up depends onthe type, duration, and severity of the employee symp-toms. If symptoms do not improve within the expectedtime frame, the employee should be referred to an appro-priate medical specialist and/or the job should be ana-lyzed again.

When the employer has determined, based onthe medical evaluation and exposure information (jobdescription, walk through, etc.), that an employee has aWMSD, he or she should perform a job analysis of theemployee’s job or a sample of representative jobs andinclude input from the symptomatic employee.

3.6 Job Analysis

Job analyses are more detailed studies of the work thanjob surveys. Job analyses identify potential exposures towork-related risk factors and evaluate their characteristicproperties.

Perform job analyses:• When it is suspected that an MSD is work re-

lated.• When a problem job is identified from a records

review, a trend of WMSDs, or job surveys.


• When a problem persists after changes have beenimplemented.

• During the design or acquisition phase ofequipment, processes, or jobs.

Work-related risk factors are present at varying levelsfor different jobs and tasks. The mere presence of arisk factor does not necessarily mean that an employeeperforming a job is at undue risk of injury. Generally,the greater the exposure is to a single risk factor orcombination of risk factors, the greater the probability ofa WMSD. For example, the risk associated with the firstthree risk factors may be increased in the presence ofcold temperature (see Bernard, 1997; National ResearchCouncil & Institute of Medicine, 2001).

Consider the following work-related risk factorsin job analysis:

• Force and contact stress. Can include tasksother than keyboarding work as well, includinggripping heavy file folders and heavy manualmaterials handling work

• Posture and motions• Vibration• Cold temperature

Evaluate WMSD risk factors for the followingexposure properties of the physical stresseslisted above by qualitative or quantitative ap-proaches:

• Magnitude• Repetition• Duration• Recovery

Also consider work organization factors that can alterthe characteristic properties or effects of physical stressexposure.

Work-related risk factors may pose minimal risk ofinjury if sufficient exposure is not present or if sufficientrecovery time is provided. However, if there is sufficientexposure and insufficient recovery time, there will be arisk of injury. Reducing exposure to risk factors willresult in reduced probability or severity of WMSDs.When work-related risk factors and their correspondingexposure properties are identified and prioritized from ajob survey or analysis, job design or redesign, includingfeasible engineering or administrative changes, caneliminate or reduce exposure to work-related riskfactors. The decision regarding which specific riskfactor to reduce in job design or redesign is based onthe scientific evidence, professional judgment, technicalfeasibility, and input from employees and management.

3.7 Job Design and InterventionThe job design and intervention process ends when:1. exposures to work-related risk factors are

reduced or eliminated as much as practical orsurveillance indicates that the problem is undercontrol or

2. appropriate exposure limits have been identifiedand met.

4 OFFICE FURNITURE DESIGN

Visual display terminals have been a subject of someconcern as their use in business and industry hasbecome almost universal. VDT technology improvesproductivity and simplifies work, but it also has thepotential to cause problems when poor workplace designis coupled with high keying rates. Most of the reportedproblems have involved dedicated or full-time operatorswho use their VDTs for 4 or more hours a day.

Complaints have included back, neck, and wristpains, eye strain, headaches, and stress. These symptomsare often associated with the fatigue and discomfort thatcan result from poor installation of VDT equipment.Applying ergonomic principles to the design of VDTworkstations can alleviate many of these problems.

A well-designed VDT workstation will allow theoperator to sit with good posture, see the screen clearly,and reach the keyboard and document easily. Operatorcomfort and sufficient room to work are key factorsin improving productivity and reducing complaints.The best workstation designs allow independent heightadjustment of the screen, keyboard, and chair. Manymanufacturers now offer workstations and furnituredesigned specifically to meet the ergonomic needs ofVDT users.

The diagrams and guidelines on the following pagesgive ergonomic considerations for selecting, installing,and adjusting VDTs and VDT workstations.

4.1 Seating and Viewing Considerations

The preferred chair type is a swivel chair on a five-pointbase, with a rounded front edge on the seat, easily heightadjustable by the operator. Position the monitor so thatthe gaze angle to the center of the screen ranges between15◦ and 20◦ below horizontal eye level. Always take intoaccount the vision requirements of VDT operators whowear glasses or bifocals. The following considerationsare adapted from ANSI/HFES 100 and BIFMA G1-2002(BIFMA, 2002; HFES, 2007):

Seat Height . Seat height should be adjustable by theuser within the recommended range of 15–22 in.(38–56 cm). If the operator is too short to keepboth feet flat on floor in the suggested heightrange, provide a foot rest.

Seat Depth . Adequate seat depth supports the thighsand allows the user to sit back far enough touse the lower portion of backrest without creatingpressure on back of the knees. If nonadjustable,seat depth should be no greater than 17 in.(43 cm). If adjustable, seat pan adjustment rangeshould include 17 in. (43 cm) or less.

Seat Pan Angle. Seats may be designed with a fixedor adjustable seat angle (e.g., recline backward orforward from horizontal). If fixed, seats shouldbe within the range from 0◦ (horizontal) to 4◦rearward. If adjustable, seats should include somepart of the range from 0◦ to 4◦ rearward.

Backrest Height . The backrest provides support forthe back in various postures. The top of the


backrest should be at least 18 in. (45 cm) abovethe compressed seat height.

Lumbar Support . This helps maintain the naturalcurvature of the spine at the small of the back.The lumbar support area of the backrest shouldbe located between 6 and 10 in. (15 and 25 cm)above the compressed seat height.

Seat Pan–Backrest Angle. Studies have shown that arecline angle of 30◦ from vertical reduces fatigue.The torso-to-thigh angle should be at least 90◦.If adjustable, the backrest should recline at least115◦ from vertical.

Armrest Height . Proper armrest height supports theneck and shoulders. Armrests should be adjust-able from 7 to 11 in. (18–27 cm) above com-pressed seat height. All armrests should bedetachable.

Eye-to-Screen Distance. Preferably at least 20 in.(51 cm); minimum 12 in. (30 cm).

Angle between Upper Arm and Forearm. Elbowangle between 70◦ and 135◦ is recommended.

Work Surface Height . Should accommodate theuser population. Minimum range of adjustabilityshould be 28 inches (56 cm to 72 cm) from floor.

4.1.1 Seated Postures

It is expected that VDT users will frequently changeworking postures to maintain comfort and productivity.Four reference postures (see Figure 3) are recognizedand commonly observed at computer workstations.Movement within these postures is encouraged.

These working postures are acceptable as long as theworkstation has been properly adjusted to the employee.Standing posture can occur when working at standingworkstations or when getting out of a chair to do otherwork, for example, retrieving items from a printer.

4.2 Work Surface and Seated ClearanceConsiderations

The keyboard should be thin and detached from the con-sole, and the mouse or track ball should be at the samelevel as the keyboard. Clearance guidelines are designed

to accommodate upright, reclined, and declined sittingpostures. The items that follow are adapted from ANSI/HFES 100 and BIFMA G1-2002 (BIFMA, 2002; HFES,2007):

Work Surface Width . At least 27.5 in. (70 cm) wide.Palm Rest Depth . Minimum 1.5 in. (3.8 cm).Input Device Support Surface. For sitting postures,

adjust in height per work surface height recom-mendations.

Thigh Clearance (Height). If not adjustable, no lessthan 27 in. (68 cm) at front edge of work surfaceand 25 in. (64 cm) at 17 in. (43 cm) rearward fromfront edge of work surface. If adjustable, it shouldinclude a height clearance of 27 in. (68 cm) as partof the adjustment range.

Thigh Clearance (Width). No less than 20 in. (50 cm).Knee and Feet Clearance (Depth). At knee level, no

less than 17 in. (44 cm) deep and no less than23.5 in. (60 cm) deep at foot level. Work surfacedepth should allow for knee and feet clearances anda viewing distance to monitor of at least 19.7 in.(50 cm).

4.2.1 Chair Selection Tips

• Chair adjustment controls should be easilyoperable from a seated position.

• The chair and adjustment mechanisms should berugged.

• Supply chairs with both detachable and adjust-able armrests. Remove them if they interfere withthe task.

• Seat should be padded for comfort.• Several chair styles should be available to

accommodate different sizes and preferences ofusers. Seat pan adjustment is often an optionalaccessory so beware that one size chair may notfit all.

• Back-tilt tension should be adjustable.• The chair should permit alterations in posture

and freedom of movement.

(105–120°) (between 90 and 105°) (>90°)

Reclined sitting Upright sitting Declined sitting Standing

Figure 3 Reference working postures. (Based on, and adapted from ANSI/HFES 100-2007; HFES, 2007.)


• The backrest should be contoured to conformwith the curve of the lower spine.

• Chair fabric should allow ventilation.• Be sure that repair service is readily available.

4.2.2 Minimizing Glare

• Position screen at right angles to windows.• Adjust the tilt and swivel of the monitor.• Reduce bright outside light by means of curtains,

drapes, or blinds.• Adjust lighting levels to the range of 200–500

lux (20–50 foot candles).• Use parabolic diffuser grids or indirect lighting

to help reduce overhead lighting glare.• Provide work surfaces with an antiglare (matte)

finish.• Moveable task lights are often helpful.• Screen filters and/or hoods can also be used if

necessary.

4.2.3 Additional VDT Considerations

• VDT Stands . Height adjustability is preferred.Liquid crystal displays (LCDs) take up much lessroom and are much lighter than cathode ray tube(CRT) monitors.

• Color Displays/Monitors . Select a light highlightcolor that contrasts with the characters.

• Black-and-White Monitor . Rare these days, butselect a light background and dark characters.

• Flicker . Screen should be readable with noperceptible flicker (rate at which images are“refreshed” on a screen from scanning of theelectron gun). Not an issue with LCD flat-paneldisplays.

• Printers . Acoustical enclosures are recom-mended if sound levels exceed 55 dBA.

• Ventilation . Additional ventilation or air condi-tioning may be needed to overcome heat gen-erated by many VDT workstations in a room.LCD flat-panel displays are much more energyefficient than CRTs.

• Cables and Cords . Should be concealed, cov-ered, or out of the way.

• Training . Train all operators how to adjust chair,workstation height, and VDT position.

Computers in the workplace include desktop unitson workstation furniture in office and work-at-homeenvironments and laptop or notebook computers usedvirtually anywhere. Either way, discomfort associatedwith computer use can be traced to improper workstationadjustment and use. Surveys have shown that peoplewho operate computers and VDTs are more comfortableand experience less discomfort when their workstationsare adjusted properly. The importance of getting a goodergonomic match between the operator and the work isclear. But how do you create that match?

5 GETTING A GOOD ERGONOMIC MATCHBETWEEN OPERATOR AND WORKSPACE

5.1 Talk to Your EmployeesAn investment in office furniture with the latestergonomic features can be wasted unless operators aretaught to adjust their workstations correctly and unlessmanagement follows through to see that the adjustmentsare made. Keyboard work is demanding. Let youremployees know that you are concerned with theircomfort and you want to minimize the physical stress ofworking with the computer. Figure 4 shows the factorsthat you need to consider to ensure operator comfort.

5.2 Making Height AdjustmentsTwo methods are common for performing computerworkstation assessments. They include observationaltechniques that estimate correct height through knowl-edge of “neutral” posture and direct measurement tech-niques.

5.3 Direct Measurement TechniquesMeasure each operator individually to determine theappropriate height adjustments for their workstations.Seat the operator on a table or desk as shown in Figure 4,so that the edge of the tabletop just touches the back ofthe knees.

5.4 Operator Measurements (Dainoffand Dainoff, 1986)

A = Knee HeightMeasure from the crease behind the knee to the

bottom of the heel. Make sure the person iswearing the type of shoes normally worn on thejob.

B = Elbow HeightMeasure from a fixed surface, that is, tabletop, to the

tip of the elbow. The person should be relaxed butsitting up straight. This measurement is easier ifthe person holds the upper arm against the bodyand reaches the hand toward the neck.

C

B

A

Figure 4 Operator measurements.


C = Eye HeightMeasure from a fixed surface, that is, tabletop, to

the eyes. Again, the person should be relaxed butsitting up straight.

5.5 Adjust the Chair Height

Once you have measured knee height (A), elbow height(B ), and eye height (C ), set the height of the chair frontat knee height (A) initially. The seat pan may drop aninch or two when the operator sits down. If this is thecase, raise the seat pan to offset the height change.

It is important the employee be trained on everychair adjustment feature. Some adjustment features areoptional, for example, the seat pan adjustment.

Manufacturers may offer different size chairs, forexample, small, medium, and large chairs to allow forlonger legs. Make sure the employee has been fitted withthe right chair.

If the seat is too high and cannot be lowered to theappropriate level, get a footrest and adjust the seat sothat the vertical distance between the footrest and thefront edge of the seat is equal to knee height (A).

If the seat pan has a tilt mechanism, the operatorshould tilt the seat to the most comfortable angle forwork. In jobs that require a lot of data entry, such asword processing, some operators prefer a forward-tiltedseat. For less-intensive keyboard work, many operatorsprefer a backward-tilted seat. Tilting the seat pan usuallychanges the height of the seat; readjust the front edgeof the chair to knee height (A).

5.6 Position the Keyboard and Mouse

The center (or home) row of the keyboard should beadjusted to a height equal to knee height plus elbowheight (A + B ) above the floor, as shown in the lowerportion of Figure 5. If a footrest is necessary, its heightshould also be added. The intent is to place the centerrow level with the tip of the elbow, thus keeping theforearms in a horizontal position.

If the keyboard height is not adjustable, raise orlower the chair height so that the difference in height

A + B

A + C

A

Figure 5 Desired workstation heights.

between the chair seat and the keyboard is equal toelbow height (B ). Provide footrests if needed.

If the keyboard is thin (1–1.5 in.), place it about 2 in.back from the edge of the table. If the operator is usinga thicker keyboard, provide a padded palm rest.

The mouse or input device should be at the samelevel as the keyboard. If using a keyboard tray, the trayshould be wide enough to accommodate the mouse.

5.7 Position the MonitorThere are a variety of visual displays used in officesand they include CRT monitors and flat-panel LCDmonitors. Configuration can be a single monitor or dualmonitor set-up.

• Raise or lower the display so that the top of thescreen is level with or slightly below the eyes,about equal to knee height plus eye height (A +C ). If the operator wears bifocals or trifocals, alower position may be more comfortable.

• Position the display at least 20 in. away from theoperator’s eyes or at arms length.

• For tasks in which the operator must readdocuments in addition to looking at the screen,move the visual display right or left of center tomake room for a document holder (see Figure 5).

• Darken the screen while the operator checksfor light reflectance or glare. Tilt the screento eliminate as much glare or reflectance aspossible. If the screen is right or left of center,moving it to the other side may help reduce glare.

5.8 Dual-Monitor Guidelines

• Both monitors should be matched in size andquality (luminance and contrast). If not matchedin size, center viewing angle for documents onboth screens should be the same.

• Flat-panel displays should not be paired withCRT monitors if possible.

• Both monitors should be placed at the sameheight and viewing distance. Viewing distanceto each monitor should be a minimum of 20 in.or arms length away.

• Place both monitors as close to each other aspossible.

• Provide adjustable monitor stands that are secureand allow for adjusting vertical height, screentilt, and screen angle.

• Set up one monitor as the primary and the otheras the auxiliary screen. Place the computer screenthat is used more frequently closer to the centerviewing angle and the auxiliary monitor to theside, left or right, and slightly angled toward theemployee.

5.9 Laptop ComputersLaptop computers are no longer just for people whospend a large portion of their time away from a tra-ditional office. Workers who rarely leave their officeare using them too. Unfortunately this has led tocomplaints of back, neck, and wrist pain because the


laptop is designed for portability, not ergonomics. Withthe keyboard and screen attached as one unit, the usermust decide between a comfortable head and neckposition or a comfortable wrist and arm position.

When discussing the use of laptop computers, thereare two situations to consider:

1. An operator in an office environment with adocking station, external monitor, keyboard, andmouse

2. A mobile worker who uses laptops in airports,hotels, or offices without any external devices.

Operators in an office environment with an externaldevice should follow the same height adjustmentguidelines mentioned above. Mobile worker solutionsare more challenging.

5.10 Positioning the Laptop

Positioning a laptop can be a challenge as placing thelaptop low (in your lap or on a desk) for comfortable armposition means that you have to tilt your neck forwardto view the screen; raising the screen to an acceptablelevel means that your hands are now reaching too high.

Some prefer placing the laptop on the work surfacedirectly in front of the operator with the back elevatedslightly to raise the display height. This can beaccomplished inexpensively using specially designedlaptop stands or three-ring binders with the binder atthe back of the laptop. This also angles the keyboard,which may or may not be desirable. Tilting the screentoo far may increase glare from overhead lights. Screendistance would follow the same guidelines as above.

Other operators prefer raising the entire laptop usinga monitor stand or other means so the screen is ateye level and using an external keyboard and mouse.Inexpensive and portable monitor stands and externalkeyboards are readily available from mobile workerergonomic accessory vendors and websites.

5.11 Other Considerations

Instruct the operator to:

Use a light touch when keying or using the mouse.Use the index and middle fingers instead of the thumb

to move the cursor via the touch screen. Movethe hand toward the touch screen to eliminatestretching the fingers and alternate between hands.

Take short breaks every 20–30 min.Use a bag with wheels when transporting the laptop.

If the operator must carry the laptop, use a bag with awide shoulder strap and alternate between shoulders.

Minimize the weight by carrying only what isneeded. Reduce the number of peripherals such as discdrives and CD-ROM drives.

6 EYE STRAIN AND FATIGUE

While CTS may be the most infamous and possibly themost costly of all WMSDs, it is NOT the most prevalentmalady of those who spend most of the working day

interfacing with a computer. That distinction goes to yetanother acronym, CVS, or computer vision syndrome.

The American Optometric Association (AOA) definesCVS as that “complex of eye and vision problems relatedto near work which are experienced during or related tocomputer use” and one that is very common among VDTworkers (AOA, 2010). The following studies illustrate theimportance of vision and visual fatigue on performanceand safety associated with computer work:

• Visual symptoms occur in 50–90% of VDT work-ers while a National Institute for OccupationalSafety and Health (NIOSH) study showed that22% of VDT workers suffer from the more tradi-tional musculoskeletal disorders (NIOSH, 1981).

• A survey of optometrists indicated that 10 millionprimary eye care examinations are providedannually in this country because of visual prob-lems at VDTs (Sheedy, 1992).

• A 2000 NIOSH study concluded the additionof supplemental breaks such as a 5-min breakduring each hour decreased musculoskeletaldiscomfort, eye strain, and mood and did notaffect performance in data entry workers (Galinskiet al., 2000). A follow-up study published in 2007provided further evidence that supplementarybreaks reliably minimize discomfort and eyestrainwithout impairing productivity (Galinski et al.,2007).

On the human side of the VDT, the visual symptomsof an unsound interface have been broadly classified as“asthenopia,” which is Greek for “MY EYES HURT,”or as defined by the Dictionary of Optometry and VisualScience, “a subjective complaint of uncomfortable,painful and irritable vision” (Millodot, 1997).

On the process side of the VDT the symptoms ofan unsound visual interface are work mistakes and lostproductivity. A study that examined the relationshipbetween the vision of computer workers and theirproductivity was conducted by the School of Optometryat the University of Alabama in Birmingham (Daumet al., 2004) and found a direct correlation betweenvision correction and process speed and accuracy.

6.1 CVS: Symptoms, Causes, and Controls

6.1.1 Eye Muscle Fatigue/Strain

The energy for all structural movement in the bodyis provided by muscles and the movement of the eyeis no different. The two primary muscle groups thatare impacted by near work like viewing a computerscreen are the large extraocular muscles that providefor the multidirectional movement of the eyeball andthe smaller ciliary muscles that are attached to the lenscapsule of the eye and provide the force necessary tochange the lens shape when we focus on an object.Much of the eye irritation attributable to near-viewingactivities like computer work is associated with thefatiguing and straining of these muscle groups.


6.1.2 Extraocular Muscle Strain/Fatigue

To understand how the extraocular muscles becomefatigueg and strained, we must review the concept of the“resting point of convergence,” which is that distanceat which the eyes no longer need to cross to view anobject. For most people the resting point of convergenceis ≈40 in.

As the object we are viewing moves closer than 40in., the medial rectus muscles will contract and pullthe eyeballs inward toward the nose. This movementis called convergence and allows the eyes to maintainthe alignment of the object we are viewing on the sameplace in both retinas, thus preventing double images.The closer the object, the stronger the contraction of themuscle and the more the muscle strain. Extended nearviewing requires a prolonged contraction of the medialrectus muscles and increases the risk of muscle fatigue.

6.1.3 Ciliary Muscle Strain/Fatigue andBlurred Vision

To understand how the ciliary muscles become fatigueand strained, we must discuss yet another resting point,the “resting point of accommodation,” which is definedas that point where the eye focuses when there isnothing to focus on. The resting point of accommodationwill vary slightly from person to person but is ≈31 in.for young people and will increase with age. At thisdistance, the ciliary muscles, which focus the lens, willnot be contracted.

As the object we are trying to focus on moves closerthan ≈31 in., the small ciliary muscles will begin tocontract to flex the lens into focus. The closer the focalpoint, the stronger the contraction of these muscles andthe more opportunity for muscle strain. The risk ofciliary muscle fatigue also increases when our visualwork area requires frequent changes of focal distances.These changes in focal distance are accommodated bythe ciliary muscles repeatedly contracting and relaxingto change the shape of the lens and thus keep the visualobject in focus.

6.2 Control Options for Eye Muscle Strain andFatigue

6.2.1 Monitor Distance

The closer the monitor, the more convergence andaccommodation are required. By moving the monitorback, the load on both the extraocular and ciliarymuscles will be reduced.

If you can see what you’re looking at, the screen isnot too far away. The only practical limit on how faraway the monitor can be is the size of the letters and theworkstation configuration. Fortunately many softwareprograms allow us to change the font size, enabling us towrite and edit with a larger font which is then changedbefore printing.

6.2.2 Monitor Height

Because the resting points of convergence and accom-modation both move inward with a downward gazeangle, lowering the monitor reduces the demand on these

muscular systems. For example, a horizontal viewingangle has a resting point of convergence of ≈45 in. whilea 40◦ downward viewing angle has a resting point ofconvergence of only 32 in.

6.2.3 Focal Distance

• As much as possible keep all frequently accessedvisual targets at a similar focal distance and inthe same vertical plane.

• The use of a vertically oriented document holderhelps to keep both the monitor screen and hardcopy in approximately the same focal distance.

6.2.4 Vision BreaksAnother way to reduce visual stress is to take “vision”breaks by looking at something that is well beyond yourresting points of accommodation and convergence. Weare all familiar with the term 20/20 as the descriptor ofnormal visual acuity. Just add another 20—20/20/20—and you have a great memory jogger for a visualwork/rest regime.

Every 20 min take 20 s to focus on an object at least20 ft away (Anshel, 1998).

7 MOBILE WORKERS: MANAGING SAFETYOF TELECOMMUTERS

Implementing a managed safety process is critical tooptimizing the working environment of telecommuters,reducing the risk of claims and injury costs, and increas-ing profits. Key stakeholders inside and outside theorganization are essential to the success of this pro-gram. Obtaining accurate and complete injury dataand hazard information to effectively manage telecom-muter safety is a challenge for managers. Three surveil-lance approaches are recommended by Robertson et al.(2003):

1. Employee Reports . Prompt reporting of haz-ards, injuries, or symptoms to the employer isimportant for treatment and prevention. How-ever, some telecommuters are reluctant to doso, fearing that reporting work-related hazardsor injuries may result in the cancellation of thetelecommuting agreement. Rather than report awork-related injury, some may visit their per-sonal physician and rely on health insurance topay the bill.

2. Review Existing Records . Records such as work-ers compensation claims, reports, and OSHAlogs provide valuable information. Check withyour workers compensation (WC) insurer tomake sure worker injuries occurring off-site areproperly coded and tracked in your itemized lossstatements.

3. Job Surveys . These include checklists and sur-veys dealing with hazards. Employers may notknow what hazards exist in the home envi-ronment unless the worker voluntarily offersthe information. Most companies rely on self-assessments of at-home workplaces.


Table 3 Telecommuter Safety Program Evaluation

01. Do you offer guidelines for setting up a home office, including equipment and ergonomic accessories, and providegeneral recommendations?

02. Do you have self-assessment surveys for ergonomics, computer workstations, and home hazards? If so, are thesesurveys administered online or by hard copy?

03. What do you do with surveys after you receive them? What kind of follow-up exists to determine whether hazardsare corrected?

04. How is survey data collected, analyzed, and used for improving safety at off-site environments?05. Do you have a policy addressing what ergonomic accessories and office furniture will be paid for by the company?06. Do you offer training programs for work-at-home workers that include risk factors, ergonomic solutions, symptom

recognition, and reporting? If so, are the training programs administered via the intranet, hard copy, or other means?07. Do you assess whether training is completed and learning has taken place?08. Is there a procedure for reporting computer and systems problems that impact the work-at-home employee? Are

these problems promptly resolved? Do you know that for sure?09. How do work-at-home employees report symptoms and general health concerns they feel are work related? Do they

feel they can do so without reprisal of job action? Is confidentiality of reports maintained?10. Does your WC insurer offer site coding in their claims databases for identifying injuries that occur to at-home or

off-site workers? Do you use these data for determining safety and risk management priorities for off-site workers?11. Do you have a return-to-work strategy for disabled workers who work at home or off-site? Are workers able to

receive quality health care? How do you know?12. Do work-at-home employees communicate regularly with their managers and peers, and are they kept current on

company happenings?

If you have a safety program that addresses work-at-home employees, evaluate its effectiveness by answer-ing the questions in Table 3 (Robertson et al., 2003). Ifan answer is “no” or “I don’t know,” target the item forimprovement.

7.1 Tips for Working at Home

If you are considering a work-at-home policy, there areseveral issues to consider in order to maintain a safe andcomfortable work-at-home environment.

7.1.1 Planning the Workspace

Identify a location that provides you with a physicallyseparate workspace, preferably away from the flow ofactivity in your house. Interruptions by family memberscan be distracting.

When planning your space needs, a good rule ofthumb for space allowance is to identify, at a minimum,a 6 × 6-ft space for your primary work area. Expectspace requirements to grow depending on what you needfor references or storage. Lateral files typically have afootprint of 36 in.× 18 in. while vertical files are 15 in. ×18 in. Bookcases require additional space.

Bookcases and filing cabinets should be placed sothat one needs to stand up to access them. Walk aroundperiodically. Do not sit continuously throughout the day.Plan movement into your office design and recognizethat this adds to the space requirements.

Do not put your office in a small room withoutwindows. A closed room needs two doors out for lifesafety. Ideally, you should have ready access to a viewgreater than 12 ft away. A window makes this easy. Thelonger view will allow the eye muscles to relax.

Avoid placing the computer next to a window.Windows that are close by create problems with visually

demanding work because of the glare. It is best to find aspace on a north wall. Be careful of extension cords andwiring that crosses the travel area, as they can producetrip and fall hazards. All cables and extension cordsshould be fastened up and out of the way.

Be sure you have a lockable door and can controlentry into your work area. Try to have an understandingwith family members or roommates that you needprivacy to conduct business in a professional manner.

Your work area should have at least two means ofegress. One way out can be a window if you have a safemeans of getting from the window to the ground.

Select a location with access to sufficient electricalpower outlets. If you have any questions about electricalsupply, have a licensed electrician evaluate your needsand install additional outlets if necessary. Residential-type extension cords are not a good choice; look fora cord with a minimum of 14-gauge wire. If a powerstrip is used, look for types with surge and overloadprotection.

7.1.2 Selecting FurnitureSelect your furniture carefully, especially your deskand chair. If your company provides furniture, knowin advance where you intend to place it to be sure itwill fit. If you are purchasing the furniture yourself,check with your manager or someone who is familiarwith getting surplus furniture. Your desk will need toaccommodate your computer, keyboard, phone, paper,references, stapler, sundry items like pen holders andpaper clips, and possibly fax, CD drive, scanner, andprinter; therefore desktop dimensions are important.

Watch out for the cheap office furniture in advertisingfliers. This furniture offers little flexibility in monitorplacement and adjustment. Those with cubby holes forthe components can create problems if you have a large


terminal, want to use a document holder, or want to usea slant board to hold books or other large references.Sometimes leg space is inadequate as well.

If you have a typical VDT monitor, you will need awork surface with at least 30 in. depth. A work surfacewith less depth is going to create problems. It is notunusual to find that the depth of the terminal combinedwith the depth of the keyboard exceeds 24 in. In thiscase, you will need to install a keyboard support or tray.

Do not place the monitor to the side of the keyboard.This is a poor solution because your neck was notdesigned to be held in a twisted position and you willeventually begin to develop neck and shoulder pain.

The desk may have a fixed-height work surface orit may be adjustable. Adjustable is better because youwill be able to set it at the correct height for you.Fixed-height desks or workstations are usually in therange of 28–29 in. This is a problem for many people.Some may find the keyboard is too high, even whenusing a standard office chair adjusted to its highest point.This requires an adjustable keyboard holder to bring thekeyboard down to a comfortable position.

Keyboard trays or holders should be at least 26 in.wide and at least 10 in. deep or more. Keyboard holdersor trays have some serious trade-offs. They are generallynot as stable as a desk top and can be loose or bouncy.Trays push you away from the working surface andeverything you have on that surface. The phone is harderto reach, you often have to stretch out your arm and getinto awkward positions just to write, and you will findyourself leaning and stretching out to read documents.

Select a solid, substantial desk or workstation thatdoes not tip over when loaded up or when an overloadeddrawer is pulled out. Beware of raised edges, and lookfor good leg clearance (at least 17 in. deep at the knee)and a matte finish. Center-drawer desks are not a goodchoice because the drawer will not allow the keyboardto be adjusted to the correct height for you and still leaveadequate leg clearance. A table is better, as long as thesurface has cantilever support or is otherwise designedso there is no part of the frame impinging on leg room.

The chair is a critical component to your homeoffice. A typical chair will create problems. Look for acommercial office chair with height adjustability, back-tilt mechanism, lumbar support, and a seat pan thatis the right width and length. Select one wisely aftertrying some out. Most office chairs adjust in the rangeof 16–21 in. Even at 16 in., about 15% of the femalepopulation and 2% of the male population will needfootrests.

Your chair should have a five- or six-point swivelbase with wheels and a rounded or waterfall front edge.Some seat pans are strongly contoured; these can bea problem for some people. Be careful that armrestsdo not stop you from bringing yourself up close to thekeyboard. If the chair has armrests, be sure they areneither too low, in which case you will be slumpingin the chair all day, nor too high, in which case yourshoulders will be raised into an unnatural posture.Armrest adjustability is preferable. The backrest shouldnot be so wide that your elbows bump it.

Filing cabinets can be dangerous for young children.If upper drawers are pulled out and children climb onthem, the cabinet can tip. Look for a means to securethe filing cabinet such as securing one to another orsecuring to a wall.

7.2 Using a Laptop Computer at Home

Many laptops lack the image clarity of a full-size VGAmonitor and can create eye discomfort. Docking systemsand simply attaching a full-size terminal are goodsolutions for those whose work requires a substantialamount of visual interaction with the screen. A full-sizekeyboard and mouse or other pointing device should beused as well.

If you are using a laptop, even with a detachedkeyboard, work surface depth of 24 in. should be suitablebecause the units are seldom more than 12 in. deep. Thefollowing steps can minimize the onset of eye fatigueand strain when using your laptop at home:

• Take “mini” breaks by focusing on a distantobject for a few seconds before continuing workon your screen.

• Keep the screen clean at all times, using ap-propriate antistatic cleaning materials.

• It is better to make keyboard position yourprimary concern. If the keyboard is not separate,this will mean tipping the display back.

• Reflective lighting may be a source of annoyancefor laptop users. Use drapes, shades, or blinds tocontrol glare. Use indirect light whenever possi-ble while avoiding intense or uneven lighting inyour field of vision.

• Keep your head in a comfortable position, notoverly turned or tilted. Adjust the screen bright-ness and contrast levels that allow you tocomfortably view the screen. If you experiencefatigue or visual discomfort after following thesesuggestions, consult an eye care specialist andinform that specialist of your computer use.

It is certainly a challenge to maintain comfortablehand and arm positions while using a laptop. Thefollowing recommendations may help:

• Change your position often to avoid discomfortand muscle fatigue. If you begin to feel uncom-fortable, stop and rest.

• Take periodic breaks and stretch your arms,hands, and fingers. Many computer users findthat frequent, short breaks are of greater benefitthan fewer, longer breaks.

• Type with a light touch. Do not pound the keys.Make sure you are not pushing down on the keysharder than necessary.

• Keep your wrists in a straight, nonrigid position.Never position your wrists in an exaggeratedangle or in a position that causes tension in yourwrists.


• Your hands and wrists should be free to movewhen typing. Do not rest your wrists on a palmrest, a table, or your thighs while typing on alaptop.

• Keep your fingers relaxed and nonrigid whenoperating your laptop or an input device. Payparticular attention to your ring finger, pinkiefinger, and thumb. Make sure you are not tenselyholding them up in the air or scrunching theminto the side of your hand when using your inputdevice or typing.

Working with a laptop keyboard for long periods canbe uncomfortable and fatiguing. Especially problematicis a laptop keyboard for someone who must work withnumbers. A regular-size and configuration number padas a peripheral is essential for those who work withnumbers on a laptop computer.

7.3 Consider Your EnvironmentIf you have a regular light-emissive terminal, theambient lighting around the screen should not exceed500 lux (50 foot candles). If you have a flat-paneldisplay, you can increase the lighting to around 750 lux(75 foot candles). Bare incandescent bulbs do not makea visually comfortable workstation. Indirect fluorescentlighting or fluorescent lighting with diffusers that trainthe light directly downward are the best choice.

Avoid having any bright-light sources in yourimmediate field of view. The preferable location for lightsources is behind you, over a shoulder at an angle, or ata right angle to you so that you do not see a reflectionin the screen.

Walls and wall coverings should be nonreflective.Some walls have enamel paint or shiny wallpaper thatcan be very reflective. Avoid the impulse to put framedartwork or photographs in your immediate field of viewbecause they tend to have a relatively high reflectance.

Most noise at home will come from televisions,stereos, and conversation. Demanding complete quietwhile you work in the kitchen is unreasonable. Locatingyour office out of the mainstream of activity will allowyour family or roommates to conduct normal lives.

The home office should have adequate ventilation. Ifthe home has a forced hot-air system or central air, aduct should be in the work area.

Most home carpeting and carpet pads are softer andless durable than commercial carpeting used in offices.Your chair will not roll as easily and may be a problemfor you to easily change position as you perform yourtasks. A solid carpet protector can be helpful but canalso be a problem if the chair rolls too easily.

If your office is below grade, have your work areatested for radon.

7.4 Making a Good Ergonomic FitOnce you have installed your furniture and equipment,it is important to adjust your workstation to fit you.

A good ergonomic fit for your workstation includesa chair height adjustment which permits your feet torest flat against the floor and the work surface for yourkeyboard to be about 1 in. lower than your elbow height.

If workstation design does not allow adequateadjustability for keyboard height, it may be necessaryto adjust chair height to elevate your elbow about aninch above your keyboard, and support your feet with afootrest.

Position the monitor for a moderate downward gazeangle and at fingertip reach, or about 20 in. from youreyes. If you are a hunt-and-peck typist, it might be easierfor you to have a closer, lower monitor so you are notmoving your head and neck up and down. Eyes movefairly easily through an arc of about 30◦, so a fairly lowmonitor reduces A and A + B repeated neck motion. Forthose who touch type, a monitor at a higher position willprobably be more comfortable.

A word on eye wear: A very common problem ispresbyopia, the loss of the eye’s ability to see closeobjects clearly. Presbyopia is usually corrected withbifocals or trifocals. If you are a touch typist or knowthe keyboard so well that you need not do more thanglance at it occasionally, it would behoove you to getmonocular lenses to replace the bifocals while working.The strength of the monocular lens should be set forthe distance from your eyes to your screen. If you are ahunt-and-peck typist, special bifocal lenses for VDT useare a good option. In this case, the top lens is set for theterminal distance and the lower lens for the keyboard.

Document holders are often a case of personalpreference. In most cases, the home worker or hotelerwill be composing rather than transcribing, so it is oftenunnecessary to be concerned with a document holder. Ifyour work involves a lot of transcription from a printeddocument, it will be very important to have a documentholder. Generally, document holders are designed to beat the side of the terminal or between the terminal andkeyboard. The location is a matter of personal preferencebut can be influenced by whether you are a touch typist,whether you have presbyopia, and what type of displayyou are using.

If your work surface is the wrong height and youdecide to buy a keyboard holder or tray, be sure thatyou get one wide enough to hold your keyboard andmouse/mouse pad or track ball. This is usually about28 in. unless you have a split keyboard or some othertype that is wider than a standard expanded keyboard.Avoid situations where you must reach out for themouse, especially with the shoulder raised. If you havemultiple computers and terminals, it is best to get an“A–B” switch for your keyboard so you do not clutterthe desktop with keyboards and mice.

Wrist rests are not for everyone and in some casescan be a problem. A wrist rest provides a soft place torelax the hands when not typing. It should not be used tosupport the hands while typing. Hands should be cuppedand above the keyboard when typing while the wrist isstraight or very slightly extended.

8 INTERVENTION STRATEGIES

Office ergonomics studies have revealed a varietyof contributing factors to musculoskeletal and visualdiscomfort among computer users. These factors include


increased job demands and more hours working ata computer (e.g., Bernard et al., 1994; Faucett andRempel, 1994), sustained awkward head and armpostures (Marcus and Gerr, 1996; Tittiranonda et al.,1999), increased levels of psychological stress and poorpsychosocial work environment, (e.g., Bongers et al.,1993; Carayon and Smith, 2000; Faucett and Rempel,1994; Marcus and Gerr, 1996), work organizationalfactors (e.g., Lassen et al., 2004; Punnett and Bergqvist,1997), a lack of specific ergonomic features in theworkstations and office buildings, and poor lighting(e.g., Daum et al., 2004; Nelson and Silverstein, 1998;Sauter et al., 1990). Typically, these studies are cross-sectional in design and only describe the work, safety,and health experiences of computer and office workersat one time period (Demure et al., 2000). Recently, theliterature in workplace interventions intended to preventor reduce musculoskeletal and visual symptoms amongcomputer users has grown. However, few longitudinalfield or lab studies have examined the effects of officeergonomics interventions on workers’ health, safety, andperformance (Brewer et al., 2006; Buckle, 1997; Karshet al., 2001). Although there is a growing interest amongemployers to improve office workplaces, studies thatinvestigated the effects of workstation, eyewear, andbehavioral interventions on upper body musculoskeletaland visual symptoms are of mixed quality (Brewer et al.,2006; Karsh et al., 2001).

There is some evidence, however, that ergonomicstraining (Brisson et al., 1999) in workstation and build-ing design (e.g., Aaras et al., 2001; Hagberg et al., 1995;Nelson and Silverstein, 1998; Sauter et al., 1990) canprevent or reduce musculoskeletal and visual discom-forts and symptoms in office environments. One methodfor reducing the prevalence of musculoskeletal andvisual symptoms is to provide specialized ergonomicstraining and workstation changes. Office ergonomicstraining helps employees to understand proper worksta-tion set-up and postures (e.g., Bohr, 2000; Brisson et al.,1999; Ketola et al., 2002; Verbeek, 1991). Green andBriggs (1989) showed that merely providing adjustablefurniture alone may not prevent the onset of overuseinjury. However, a significant decrease in WMSDs andvisual discomfort has been observed when workers weregiven an adjustable/flexible work environment coupledwith ergonomics training (Amick et al., 2003; Robert-son et al., 2008, 2009). Further, the provision of con-trol over the work environment through adjustabilityand knowledge may enhance worker effectiveness aswell as their health and safety (Hedge and Ray, 2004;McLaney and Hurrell, 1988; O’Neill, 1994; Robertsonet al., 2008, 2009; Smith and Bayehi, 2003). Recentfindings of a randomized control trial 15-day longitudi-nal laboratory study, replicating an 8-h customer servicejob, further supported these field intervention studies. Itwas observed in this study that the trained group whoused sit/stand workstations exhibited minimal and sig-nificantly lower musculoskeletal and visual discomfortcompared to a nontrained reference group also work-ing in the same sit/stand configuration. Moreover, thetrained group had significantly higher performance andeffectiveness than the reference group as exhibited by

higher accuracy and quality control scores (Robertsonet al., 2010). These findings, which indicate the abilityto mitigate symptoms, change behaviors, and enhanceperformance through training combined with a sit/standworkstation, have implications for preventing discom-forts in office and computer workers (Robertson et al.,2009). These results are also supported by the conclu-sions of a systematic review conducted by Brewer et al.(2006) with their critical and strict 11-point inclusioncriteria of 31 studies. In this review only moderate evi-dence was observed for no effect of workstation adjust-ment alone and no effect of rest breaks and exerciseon musculoskeletal or visual health. A positive effectof alternative pointing devices was found. They furtherconcluded that for all other workplace interventions amixed or insufficient evidence of effect was observed(Brewer et al., 2006).

When examining other office ergonomic interventionstudies that may have weaker designs, such as nonran-domized control trial or no controlled group, positive andsignificant results have been observed consisting of var-ious office ergonomics interventions (e.g., Dainoff et al.,1999; Hedge and Ray, 2004; Sauter et al., 1990; Smithand Bayehi, 2003; Smith and Carayon, 1996; Vink et al.,2009). Certainly these findings are limited in their gen-eralizability due to lack of internal and external validity;however, they do provide insightful and useful informa-tion describing the effects of various office ergonomicsinterventions in either field settings or a control labo-ratory study with limited exposure variables consistingof real world issues. Other related areas of workplaceinterventions, such as participatory ergonomics inter-ventions, have also shown mixed results (Rivilis et al.,2008). However, given mixed results of the effects ofoffice and computer interventions, it appears that, whenpossible in this field research, having the ability to con-trol some of the threats to validity can strengthen thestudy design and provide more definitive conclusions.Bridging laboratory with field intervention studies canalso provide an important link between building concep-tual models regarding office workers and associated risksand providing effective interventions and programmaticergonomic recommendations. These and future studiesgrounded in high-quality research can all contribute toreducing and preventing symptoms among workers andproviding an injury-free, comfortable, and productivework environment.

9 CONCLUDING REFLECTIONS

What are we to make of the current state of knowl-edge regarding office ergonomics? On the one hand,when rigorous methodological criteria are applied to thevast literature in the area, it is difficult to identify spe-cific biomechanical risk factors in WMSDs. Hence, psy-chosocial variables are proposed as potential explanatoryvariables. And yet, we have an extended case study bythe chief of experimental medicine at Beth Israel Dea-coness Medical Center in Boston describing his owndisabling wrist injury which he attributes to “bangingclumsily at the (laptop) keyboard for many hours at a


time” (Groopman, 2007, Chapter 7). At the same insti-tution, Boiselle et al. (2008) describe a prevalence rateof 58% of repetitive stress symptoms among radiolo-gists who spend more than 8 h per day interacting witha standard radiological archiving and communicationsystem (PACS). Symptom rates were reduced by intro-duction of and training on ergonomic workstations andchairs. The senior author of this chapter has similar per-sonal knowledge of highly motivated professionals whosuffered disabling wrist injuries attributed to prolongedcomputer use, injuries which were ameliorated by tra-ditional ergonomic solutions. At the very least, thesecase studies would seem to question simple psychosocialexplanations based on secondary gains through publicexpression of pain symptoms.

Two possible approaches to this dilemma are pro-posed for consideration.

9.1 More Complete Characterizationof Exposure

It is conceivable that current Cochrane-based method-ologies for attributing risk are more appropriate fortraditional disease vectors than for describing the com-plexities of office work. An alternative approach to char-acterizing exposure relies on Ashby’s (1956) principleof requisite variety, which states that the variety of themeasurement system must match the variety of the sys-tem to be measured.

Using the terminology of Section 1., we mightdefine a condition of maladaptive perception–actioncycles if there is a mismatch of coordination of pos-tural and supporting workstation degrees of freedomresulting in configurations of working postures in excessof some hypothetical three-dimensional spatial comfortzone (e.g., awkward posture), and such cycles proceedat a rate/pace in excess of a hypothetical temporal com-fort zone. The causes of these presumed mismatchesmight be physically based (e.g., anthropometic varia-tion, physical disability) and/or cognitive/behaviorallybased (e.g., lack of understanding regarding adjustmentmechanisms and the need to work at an appropriate workpace, lack of motivation to engage in appropriate adap-tive behavior).

The outcome of such maladaptive PACS could bediscomfort and pain. This may either resolve with thepassage of time or progress to a medically significantevent (diagnosis, compensation claim). Such pain mightresult from underlying tissue damage.

However, at the same time, we might consider thatthe impact of psychosocial factors on expressed painmight act through at least two pathways. The firstinvolves the possibility that combinations of psychoso-cial factors might create and/or enable maladaptiveperception–action cycles (e.g., increased work pace,lack of training, poor supervisory relationship, job con-tent, equipment). The second is that emotional reactionsto psychosocial stress have a direct influence on lev-els of pain (Marras et al., 2009). Unfortunately, themethodological challenges in subjecting the aforemen-tioned complex nonlinear relationships to analysis byrigorous scientific method are considerable. Of particu-lar difficulty is that the training and coaching required

to achieve adaptive control are also the same variablesresponsible for Hawthorne effects.

9.2 Focus on Quality and PerformanceA second approach is to avoid the context of medicaldiagnosis and treatment and focus instead on achiev-ing optimal and high-quality work performance. Bythis approach, maladaptive perception–action cycles areregarded as problems of management and work organi-zation. As has been seen in Section 8, there is consid-erable evidence that the ergonomic practices discussedin Sections 3 through 7 can result in improvements inwork performance and quality. Accordingly, reductionof discomfort/pain is a desirable management goal and,as such, is aligned with, rather than in conflict with,safety and health concerns (see, e.g., Dul and Neumann,2009). In fact, in an extensive telephone survey of over28,000 working adults, Stewart et al. (2003) determinedthat common pain at work is responsible for an annualloss of $61.2 billion in productivity in the United States,the bulk of which comes from reduced performancewhile at work. It might, therefore, be argued that use ofergonomic knowledge to provide an appropriate worksystem ought to be focused on optimizing overall workperformance and quality and, having done so, the safetyand health benefits are likely to result “for free.”

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