Original Article J. Phys. Ther. Sci.19: 151–163, 2007

The Effects of Exercise and Rest Breaks on Musculoskeletal Discomfort during Computer Tasks: An Evidence-Based Perspective

RONALD DE VERA BARREDO1), KELLY MAHON2)

1)The College of Health Sciences, Tennessee State University: 3500 Jhon A Merritt Bonlevard,Nashville TN 37209, USA.

2)The Graduate program in Physical Therapy, Arkansas State University

Abstract. OBJECTIVE: To review the strength of research evidence on the effects of exercise and restbreaks on musculoskeletal discomfort during computer tasks and compare the evidence with clinicalguidelines. SIGNIFICANCE: The review of research evidence and its comparison with current clinicalguidelines provide clinicians with knowledge to make clinically sound decisions in the care andmanagement of individuals with musculoskeletal discomfort during computer tasks. METHODS: Articlesfrom Pubmed, Ovid and references of relevant articles were reviewed for research design and internalvalidity. Grades of evidence were assigned based on the aggregate strength of articles for each intervention.RESULTS: Fifteen articles (one on exercise, seven on rest breaks, five examining both) met the inclusioncriteria. Exercise and rest breaks were each assigned a grade of C. CONCLUSIONS: Evidence supportsthe use of exercise and rest breaks in reducing musculoskeletal discomfort in computer tasks. The researchevidence suggests no additional benefits of exercise over rest breaks alone. Research evidence concurswith the clinical guidelines recommended by OSHA and the Official Disability Guidelines.Key words: Computers, Musculoskeletal, Exercise

(This article was submitted Nov. 13, 2006, and was accepted Jan. 18, 2007)

INTRODUCTION

Computer use frequently causes musculoskeletaldiscomfort1–13) which, according to a survey of theliterature, may include muscle tension, musclefatigue, paresthesia, pain, and/or physical strain insoft tissues and bones7, 14–17). The incidence ofmusculoskeletal discomfort in computer users is ashigh as 50%5, 18). Musculoskeletal discomfort hasbeen reported by computer users, either separatelyor in aggregate, in the neck, shoulders, elbows,wrists, hands, back, legs, buttocks, ankles, feet, andchest3–10, 12, 13, 15).

Many interventions have been implemented to

decrease musculoskeletal discomfort in computertasks. The interventions include individual,organizational, and ergonomic modifications.Ind iv idua l in t e rven t ions inc lude rou t ineexercise16, 19, 20) and smoking cessation19, 21). Theorganizational modifications include: increasedwork task variety, decreased hours of computer useper day3, 4, 21, 22), increased rest break opportunities,and exercise opportunities11, 12, 16, 23).

Ergonomic changes to the computer workstationare the most frequently employed intervention.Ergonomic interventions are not sufficient forcomple t e ly e l im ina t i ng muscu lo ske l e t a ld i scomfor t 7 ) . In some cases , e rgonomic

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in te rven t ions have caused no changes inmusculoskeletal discomfort. Therefore, workorganizational factors must be incorporated.

Workstation exercises and supplemental restbreaks are examples of organizational interventions.The y a r e i nex pe ns ive a nd a dva n t ag eou sinterventions aimed at decreasing musculoskeletaldiscomfort in computer tasks10). As separateinterventions, exercises and rest breaks have beenattributed to increased productivity in computertasks16) such as work with computers, video displayterminals (VDT) and data entry tasks.

Many exercises have been recommended todecrease musculoskeletal discomfort, with varyingdegrees of efficacy24, 25). They consist primarily ofstretching and relaxation techniques, which can beperformed at the computer workstation (with theexception of walking) in ten minutes or less.

Rest breaks have also been recommended todecrease musculoskeletal discomfort. Toward thisend, studies have reported that limited opportunitiesfor rest breaks are a major causative factor in manymusculoskeletal disorders in computer users9, 10).Rest breaks, rest, and breaks in this appraisal aredefined as cessation of computer tasks. During therest breaks participants are not required to remainmotionless; however, they must not perform aspecific exercise protocol.

This study examines the effects of exercise(irrespective of technique) and rest breaks( i r respect ive of length and frequency) onmusculoskeletal discomfort during computer tasks.For the purposes of this project, musculoskeletaldiscomfort is defined as a constellation of signs andsymptoms that include muscle tension, paresthesia,pain and/or physical strain in soft tissues and bones.More specifically, this study reviews the strength ofthe current research evidence on exercise and restbreaks and compares each intervention’s strengthwith current clinical guidelines, to provideclinicians with ample evidence and workingknowledge to make clinically sound decisions in thecare and management of indiv iduals wi thmusculoskeletal discomfort during computer tasks.

METHODS

Search strategyThree search strategies were used in a literature

search. The first search strategy was conductedusing Pubmed with the following limits: publication

date 1990–April 2005, clinical query, therapy,broad-sensitive search and English. The followingsearch terms were used in the literature search ofPubmed: “Computer or VDT and musculoskeletala nd exe rc i s e , ” “ C ompu te r o r VD T andmusculoskeletal and rest,” and “Computer or VDTand musculoskeletal and breaks.”

The second search strategy was conducted usingthe Ovid portal with the following limits: 1990–April 2005, therapeutics, English, and human. Thefollowing databases were searched through theOvid portal: Cumulative Index to Nursing andAllied Health Literature (CINAHL 1990–week 2April 2005), Ovid Medline (1996–week 1 April2005), Ovid Medline in Process and Non-IndexedCitations (1996–April 1, 2005), and all Evidence-based Medicine Reviews (Database of Abstracts ofReviews of Effects, Cochrane Database ofSystematic Reviews, ACP Journal Club, CochraneCentral Register of Controlled Trials).

The third search strategy reviewed the referencesof relevant articles obtained through the first andsecond search strategies. Conference proceedingsand articles published prior to 1990 were alsoincluded if they were referenced in two or morerelevant articles.

This literature appraisal was restricted to articleswhich analyze rest breaks or exercise. Exercise andrest breaks had to be analyzed independent of othervariables to be included. Articles that examinedmult iple occupations were excluded if a l loccupations did not involve computer use. Articleshad to have clearly defined methods to be includedin this study. The articles had to describe theparameters of rest breaks. Studies with exerciseprotocols lasting longer than 10 minutes wereexcluded. Exercise breaks are often consideredbreaks supplemental to the breaks required by law.Employers are unlikely to permit employees breakssupplemental to perform exercises if the protocolsrequire longer than ten minutes to complete.

Review articles other than meta-analysis orsystematic reviews were excluded because they areprimarily l i terature reviews. Studies withparticipants from multiple occupations, in whichnot all participants used computers were excluded.

Evaluation of research evidenceEach article was reviewed and the strength of

evidence was evaluated using the AmericanAcademy for Cerebral Palsy and Developmental

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Medicine (AACPDM) method26). Developed bythe AACPDM Treatment Outcomes Committee,this method is a modification of the Centre forEvidence-Based Medicine (CEBM) method27, 28)

created by Dave Sackett and colleagues. The levelof evidence for each article was determined by itsresearch design (Table 1) and internal validity(Tables 2 and 3)26).

The AACPDM method has been used in cerebralpalsy26, 29) and knee osteoarthritis30). This methodhas been determined as an appropriate method forexamining evidence of the effects of exercise andrest breaks in computer tasks by Johanna Darrah ofthe AACPDM Treatment Outcomes Committee (J.Darrah, PhD, PT, [johanna.darrah@ualberta.ca],

email, Wednesday, April 27, 2005).After evaluating the strength of each article using

the AACPDM method, the aggregate strength ofeach intervention was evaluated using the criteriaoutlined by Sackett et al.28) (Table 4) and grades ofrecommendation27, 28) (Table 5) were given andsubsequently compared with existing clinicalguidelines.

There were two reviews of each article. The firstreview was conducted by the primary author. Thesecond reviewer reviewed the appraisals conductedby the first reviewer. In the event that the tworeviewers did not agree, the reviewers meet todiscuss their findings to gain consensus. Thismethod increased the validity of the review process.

Table 1. Research designs26)

Level Non-empirical Group Research Outcomes Research

I • Systematic review of randomized controlled trials (RCT’s)• Large RCT (with narrow confidence intervals) (N>100)

II • Systematic review of • Outcomes research (very cohort studies large ecologic studies)• Smaller RCT’s (with wider confidence intervals) (N<100)

III • Systematic review of case-control studies• Cohort study with concurrent control group

IV • Cohort study without concurrent control group (e.g. with historical control group)• Case series• Case-control study

V • Expert opinion• Expert opinion based on theory or physiologic research• Case study or report• Bench research• Common sense/anecdotes

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RESULTS

The literature search revealed three articles on theeffects of exercise breaks on musculoskeletaldiscomfort during computer tasks. Seven publisheda r t i c l e s on t he e f f ec t s o f r e s t b r eaks onmusculoskeletal discomfort during computer taskswere obtained through the literature search. Fivearticles that examined the effects of both exerciseand rest breaks on musculoskeletal discomfortduring computer tasks were obtained from theliterature search. Reviews of each article, includingjustification for the assigned level of evidence aregiven below.

Articles on exerciseFenety and Walker11) examined the short term

effects of a revised Dataspan exercise program oneleven directory assistance operators. During theexperimental period of three to five day shifts,participants took one workstation exercise breakevery 30 minutes. Musculoskeletal discomfort, asmeasured by the Body Part Discomfort Scale,increased over time during the pre-exercise andexercise testing sessions. However, discomfort wassignificantly higher during testing periods whenparticipants were not exercising. In-chairmovement was significantly greater in the exercise

test session than in the pre-exercise test session,indicating decreased postural immobility in theexercise condition.

The research design employed by Fenety andWalker11) was a non-randomized clinical trial inwhich participants served as their own controls.According to Bob Phillips of the Centre forEvidence-Based Medicine, non-randomized clinicaltrials are best understood as cohort studies (BobPhillips, MD [bob.phillips@doctors.org.uk], email,Tuesday, September 6, 2005). This design qualifiesas level of evidence IV. This study had moderateinternal validity. The lack of reliability data for theBody Part Discomfort Scale lowered the internalvalidity26).

Saltzman31) examined the impact of StretchBreak, an ergonomic software program, via acomputer assisted survey. Each stretching sessionconsisted of several stretches lasting 1–2 minutes.The participants reported that short stretch breakswere effective in reducing stiffness, muscle ache,and stress. They credited increased awareness ofthe need for frequent mini-breaks and properworkstation ergonomics to the Stretch Breakprogram. Twenty-three percent of participantsreported increased productivity and enjoymentworking at their personal computer (PC) whenusing Stretch Break.

The level of evidence based on the researchdesign of this study was V because the studyemployed a survey for all data collection. Theinternal validity was weak in this study because themeasures used have not been proven to be reliable,appropriate statistical evaluations were not

Table 2. Internal validity questions25)

1. Were inclusion and exclusion criteria of the study population well described andfollowed?

2. Was the intervention well described and was there adherence to the interventionassignment? (For 2-group designs, was the control exposure also well described?)

3. Were the measures used clearly described? Were they valid and reliable formeasuring the outcomes of interest?

4. Was the outcome assessor unaware of the intervention status of the participants(i.e., blind assessment)?

5. Did the authors conduct and report appropriate statistical evaluation includingpower calculations?

6. Were dropout/loss to follow-up reported and less than 20%? For 2-group designs,was dropout balanced?

7. Considering the study design, were appropriate methods for controllingconfounding variables and limiting potential biases used?

Table 3. Internal validity score25)

S Strong (well conducted) 6 to 7M Moderate (fairly conducted) 4 to 5W Weak (poorly conducted) 3 or less

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conducted, 43% of participants dropped out of thestudy, and confounding variables and potentialbiases were not limited26, 31).

Thompson14) conducted a study evaluating theeffects of exercise on musculoskeletal discomfortand productivity of 85 data entry operators. Duringeight-hour workdays, employees were required toperform 6.5 hours of “logged on” time. Two 5-minute exercise breaks were added to the traditionalwork day. Employees were encouraged to take the5-minute exercise breaks in mid-morning and mid-afternoon, exercise during their normal rest breaksinstead of remaining passive, perform the exerciseson personal time at work or home, emphasizeexercises which seemed to cause the mostrelaxation and discomfort relief, and take additionalmini-breaks of 20–30 seconds to stretch, flex, andshake muscles if discomfort developed. Theoperators reported reduced discomfort at work and agenerally improved physical condition outside ofw o r k . T h e r e w e r e n o n e w w o r k m a n ’ scompensation claims one year after introduction ofthe exercise program. Productivity increased 25%over the first four months of the exercise program.

The research design level of evidence was V inThompson’s14) study because formal statistical

analyses were not performed. Musculoskeletaldiscomfort was not formally assessed before orduring the exercise program. The internal validitywas weak in this study because the measures usedwere not clearly described, dropout was notreported, and confounding variables were notcontrolled by permitting large variations in exerciseprotocol amongst participants26).

Table 6 provides a summary of the analysis onresearch design and internal validity of each articleon exercise using the AACPDM tool26). A grade ofrecommendation, based on the CEBM method27, 28),is provided for exercise as an intervention formusculoskeletal discomfort during computer tasks.

Articles on rest breaksBoucsein and Thum32) performed a field study to

investigate physical comfort and emotional well-being during two different work-rest schedules forcomplex computer -media ted work . Eachparticipant worked under a long break schedule of15 minutes break after 100 minutes of work on oneday and under a short break schedule of 7.5 minutesbreak after 50 minutes of work on another day. Thetotal break time each day was 82.5 minutes, whichincluded the lunch break. Musculoskeletal

Table 4. Grades of recommendation and levels of evidence26)

Level ofGrade Therapy/Prevention, Aetiology/HarmEvidence

A 1a SR (with homogeneity) of RCTs1b Individual RCT (with narrow Confidence Interval)1c All or none

B 2a SR (with homogeneity) of cohort studies2b Individual cohort study (including low quality RCT; e.g., <80% follow-up)2c “Outcomes” Research

C 3a SR (with homogeneity) of case-control studies3b Individual Case-Control Study

D 4 Case-series (and poor quality cohort and case-control studies)

E 5 Expert opinion without explicit critical appraisal, or based on physiology,bench research or “first principles”

Table 5. Grades of recommendation26)

A Consistent level 1 studiesB Consistent level 2 or 3 studies or extrapolations from level 1 studiesC Level 4 studies or extrapolations from level 2 or 3 studiesD Level 5 evidence or troublingly inconsistent or inconclusive studies of any level

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discomfort and exhaustion increased significantlyunder both break schedules. The degree ofdiscomfort was not significantly different betweenthe two work-rest schedules. Emotional well-beingwas significantly better under short break schedulein the morning and significantly better under thelong break schedule in the afternoon.

A crossover study design without randomizationwas used by Boucsein and Thum32). No concurrentcontrol group was used in this study. Studies usingnon-randomized crossover designs are bestunderstood as small cohort studies (Bob Phillips,MD, [bob.phillips@doctors.org.uk], email,Tuesday, September 6, 2005). This study employeda level IV research design. This study had weakinternal validity. The measures used have not beenproven reliable, power calculations were notperformed, confounding variables were notcontrol led, and loss to fol low up was notreported26).

Ferreira et al.33) performed a retrospective studyon the incidence of musculoskeletal disorders of thewrists and hands in an at-risk population of femalecustomer service operators. The variables studiedincluded: age, seniority, mean daily regular worktime, overtime per operator, time pressure at work,work-rest schedule, management status, personneltraining on posture and muscle stretching, andergonomic hazards. The variables that significantlycorrelated with upper extremity musculoskeletal

disorders were time pressure at work and work-restschedule. The effects of exercise examined byFerreira et al. were not analyzed independent ofother variables. Therefore, the exercise componentof their study was not included in this evidence-based review.

A case-control study design, level of evidence IV,was employed in the study by Ferreira et al.33) Theinternal validity of the study had moderate strength.Confounding variables were not controlled anddropout was greater than twenty percent26).

Galinsky et al.9) compared the effects of aconventional and supplemental work-rest scheduleon musculoskeletal discomfort, eyestrain, andper formance in da ta en t ry workers . Theconventional schedule consisted of a 15-minutebreak in the middle of the first and second halves ofthe shift, in addition to a 30-minute lunch break.The supplemental schedule included the samebreaks as the conventional schedule, in addition to a5-minute break during every hour which did notinclude a break in the conventional schedule.Musculoskeletal discomfort increased during thework periods for both schedules. However, thedegree of discomfort was lower in the supplementalschedule in the eyes, neck, back, buttocks, entireright upper extremity, and the left shoulder, upperarm, and elbow. There was no significantdifference in productivity between the twoschedules.

Table 6. Level of evidence summary—Exercise

Internal validity questions Internal Internalvalidity validity Research Level of

Study 1 2 3 4 5 6 7 sum score* design evidence

Articles concluding exercise is beneficial

Balci, 200310) Yes Yes Yes No Yes Yes Yes 6 S II II-SFenety, 200211) Yes Yes No No Yes Yes Yes 5 M IV IV-MHenning et al., 1997 small worksite12) Yes Yes No No Yes No No 3 W II II-WSaltzman, 199832) Yes Yes No No No No No 2 W V V-WSundelin & Hagberg, 198940) Yes Yes Yes No No Yes Yes 5 M IV IV-MSwanson & Sauter, 199241) Yes Ye No No No No Yes 3 W II II-WThompson, 199014) Yes Yes No No No No No 2 W V V-Wvan den Heuval et al., 200315) Yes Yes No No Yes Yes Yes 5 M I I-M

Article concluding exercise is not beneficial

Henning et al., 1997 large worksite12) Yes Yes No No No No No 2 W IV IV-W

*S=Strong; M=Moderate; W=Weak31).Grade of Recommendation for Use of Exercise: 27 C.Grade of Recommendation for No Exercise: 27 D.

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A randomized crossover design with less than100 participants was used in Galinsky’s study.According to the CEBM34), this was a level ofevidence II research design. There was moderateinternal validity in this study because the tool formeasuring musculoskeletal discomfort has not beenproven reliable and 58% of participants dropped outof the study9, 26).

Henning et al., 199435), compared mood state,performance, and discomfort in a regimented restbreak system and a compensatory rest break system.In the regimented break system, participantsreceived a 20-second computer administered breakafter every 5 minutes of work. In the compensatoryrest break system, spontaneous pauses lasting 3seconds or longer were deducted from the length ofthe computer administered rest breaks. Participantsin the compensatory rest break condition received a20-second computer administered break after every5 minutes of work only if their spontaneous restpauses totaled less than 17 seconds. Spontaneouspauses lasting longer than 3 seconds occurred, onaverage, in 4 out of 9 possible 5-minute worksegments. Discomfort increased during the workperiod under both conditions. However, backdiscomfort was s ignif icant ly lower in thecompensatory break system. There was nosignificant difference between the two breaksystems in the other body regions, mood state, orperformance.

A non-randomized clinical trial, level of evidenceI V r e s e a r c h d e s i g n ( B o b P h i l l i p s , M D ,[bob.phillips@doctors.org.uk], email, Tuesday,September 6, 2005), was performed in Henning’sstudy. This study had weak internal validitybecause the measures used for musculoskeletaldiscomfort have not been proven reliable, dropoutwas not reported, and potential biases were notlimited due to non-random group assignment26, 35).

McLean et al.13) evaluated the impact of threedifferent microbreak schedules on musculoskeletaldiscomfort, EMG activity, and productivity incomputer operators. Participants were assigned toone of the following microbreak schedules: 20-minute interval group (30-second microbreak every20 minutes), 40-minute interval group (30-secondmicrobreak every 40 minutes), or the control group(breaks taken whenever needed). Musculoskeletaldiscomfort increased over time during the recordings e s s i o n s f o r a l l p r o t o c o l s . D e c re a s e dmusculoskeletal discomfort was reported in all

body regions studied under both microbreakprotocols compared to the no-break protocol. The20-minute interval caused the greatest decrease indiscomfort. Higher mean frequency (MNF) cyclingwas present in all microbreak protocols at the wristextensors, in the control and 40-minute intervalgroups at the neck, and in the 20- and 40-minuteinterval groups at the back. No significant changesin MNF cycling were present at the shoulder.Productivity was not significantly affected by themicrobreaks.

A randomized controlled clinical trial wasperformed in this study. RCT’s with less than 100participants, as in the study by McLean et al.13),qualify as level of evidence II research design. Thisstudy had strong internal validity26).

In the 1986 study by Sundelin et al.36), the impactof spontaneous pauses and micro pauses onmusculoskeletal discomfort and muscular loadduring VDT word-processing tasks was evaluated.Two 3–6 hour work sessions with spontaneouspauses, and one 3–4 hour work session with shortpauses of 14 seconds were introduced ten times perhour. Participants took diverting pauses duringwhich they left the workstation and short passivepauses. Increased discomfort was reported after allwork sessions. Differences in discomfort betweenthe two rest schedules were present only in the eyes.EMG recordings of the middle and lower trapeziusrevealed no difference in muscular load between thetwo rest schedules.

The study of Sundelin et al. employed a non-randomized crossover research design. The level ofevidence, based on research design, was IV in this study(Bob Phillips, MD, [bob.phillips@doctors.org.uk],email, Tuesday, September 6, 2005). The internalvalidity of this study was limited to moderatebecause power calculations were not performed26, 36).

Zwahlen et al.37) examined the effects of restbreaks and task type on musculoskeletal discomfortand productivity in continuous VDT work. Thesubjects received a 15-minute rest break in themiddle of the morning and afternoon sessions, ina d d i t i o n t o a 4 5 - m i n u t e l u n c h b r e a k .Musculoskeletal discomfort increased throughoutthe day. However, the authors concluded restbreaks are h ighly benef ic ia l for reducingmusculoskeletal discomfort. Visual discomfort,which also increased throughout the day, wassignificantly less than musculoskeletal discomfort.There was minimal difference in discomfort

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between the task types. Productivity was slightlyhigher after the rest breaks.

The research design level of evidence was V inthis study by Zwahlen et al.37) because formalstatistical analyses were not performed. Theinternal validity was weak because the measuresused have not been proven reliable, appropriatestatistical evaluations were not performed, andconfounding factors were not suff icient lycontrolled26).

Table 7 provides a summary of the analysis onresearch design and internal validity of each article onrest breaks using the AACPDM tool26). A grade ofrecommendation, based on the CEBM method27, 28),is provided for rest breaks as an intervention formusculoskeletal discomfort during computer tasks.

Articles on both rest and exerciseBalci and Aghazadeh10) compared different

work-rest schedules in data entry and simple mentalarithmetic tasks. A 60-minute work/10-minute rest,a 30-minute work/5-minute rest, and a 15-minutework/microbreak were compared. Under the 15-minute/ microbreak schedule participants receivedthree 30-second breaks and one 3-minute break perhour in addition to a 14-minute break after 2 hours.Exercises were performed during all breaks for eachwork/rest schedule, except the 30-second breaks.Neck, low back, and chest discomfort weresignificantly lower in the 15-minute/microbreakschedule than the other schedules. The highestspeed, accuracy, and performance was achieved inthe 15-minute/microbreak schedule.

Balci and Aghazadeh10) employed a randomizedcrossover design with less than 100 participants.The level of evidence was II based on researchdesign34). This study had strong internal validity26).

The effects of short rest breaks and exercise onmusculoskeletal discomfort, mood state, andproductivity at two field sites was examined in the1997 study by Henning et al.12). The operatorsconventional rest-break condition (control) wascompared to a rest-break-only condition and a rest-break-plus-exercise condition. The controlcondition included a 30-minute lunch break, and a15-minute break in the middle of the morning andafternoon. Operators had the option to split their15-minute breaks into three 5-minute breaks. Theexperimental break condition consisted of one 3-minute and three 30-second rest breaks per hour, inaddition to the conventional breaks. The exercises

required 15 seconds each to complete. Participantsin the exercise and rest-break conditions adhered tothe same break schedule as in the rest-break-onlycond i t ion . Dur ing the 30-second breaksparticipants performed one stretching exercise, andat least two exercises during the 3-minute breaks.A t t he l a rge work s i t e , t he de c r ea se i nmusculoskeletal discomfort in both treatmentgroups was not significant. Leg, feet, and eyecomfort improved under both treatment conditionsat the small work site. The improvement was onlysignificant in the breaks and exercise condition.Mood state did not change at either worksite. Therewere no significant differences in productivity at thelarge work site. Productivity increased at the smallworksite in both treatment conditions. However,the improvement was only significant in the breaksand exercise condition.

A between-participants randomized controlledclinical trial, level of evidence II, was performed atthe large worksite34). A non-randomized crossoverresearch design, level of evidence IV, was used att h e s m a l l w o r k s i t e ( B o b P h i l l i p s , M D ,[bob.phillips@doctors.org.uk], email, Tuesday,September 6, 2005). The internal validity was weakat both worksites because the measure used formusculoskeletal discomfort has not been provenreliable, and dropout rate was high12, 26).

Sundelin and Hagberg38), in their 1989 study,compared the effects of three different pause typeson musculoskeletal discomfort and EMG activityduring VDU work. Active pauses, diverting pauses,and passive pauses were each incorporated intoseparate work periods. Pauses were taken onceevery six minutes, for 15–20 seconds, during eachwork period. Discomfort ratings after each workperiod were very low. There was a tendency, but nostatistical significance, toward greater discomfortafter the work period involving passive pauses thanafter the work periods involving active anddiverting pauses. Static muscle load did not differbetween the three pause types. However, thepattern of muscle activity changed significantly inwork periods with active pauses. As a non-randomized crossover design, this research designqualified as level of evidence IV (Bob Phillips, MD,[bob.phillips@doctors.org.uk], email, Tuesday,September 6, 2005). The internal validity of thisstudy was limited to moderate because powercalculations were not performed26, 38).

Swanson and Sauter39) examined musculoskeletal

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discomfort, mood state, and productivity of 37healthy data entry operators. Both groups receivedthe following rest break schedule: 45-minute lunch,10-minute breaks after 100 minutes of work in themorning and afternoon, 30-second breaks every 10minutes during the morning and afternoon, 3-minute breaks at 50-minute intervals in themorning, and breaks after 30, 65, and 150 minutesin the afternoon. During the 3-minute and 30-second breaks, the exercise break group performedexercises while the passive break group satpassively. Musculoskeletal discomfort increased inboth conditions throughout the workday. Thegreatest increases in discomfort were reported in theback, neck, and throughout the right upperextremity. There were no differences betweengroups in musculoskeletal discomfort or moodsta te . Product ivi ty , which was measuredcontinuously throughout each work session,decreased more significantly during the afternoon inthe passive group than in the exercise break group,as revealed by post hoc analyses.

Swanson and Sauter39) conducted a randomizedcontrolled clinical trial. This study presents a levelof evidence II research design. The internal validitywas weak because the measures used were notclearly described, power calculations were notconducted, and dropout was not reported26).

Van den Heuval et al.15) investigated the effectsof software-stimulated rest breaks and exercise oncomputer workers with neck or upper extremitymusculoskeletal discomfort. Participants wereassigned to a control group, a breaks-only group, ora breaks-and-exercise group. In the breaks-onlygroup, participants took 5-minute breaks after each35-minute period of continuous computer use and7-second microbreaks after each 5-minute period ofcontinuous computer usage. The microbreaks werenot administered after 5-minute periods duringwhich participants took “natural” breaks whichwere of equal or greater duration than the softwareprompted breaks. The same break and microbreakschedule was applied to the breaks-and-exercisegroup. Participants in the breaks-and-exercisegroup performed four 45-second exercises at thebeginning of the 5-minute breaks. The severity ofmusculoskeletal complaints decreased in the neckand throughout the upper extremity in all groups.The frequency of complaints decreased in the neckand shoulder, and increased in the elbow, wrist, andhands in all groups. After adjustment for sex and

age, both intervention groups reported significantlygreater recovery from musculoskeletal complaintsthan the control group. There was no difference inrecovery from musculoskeletal discomfort betweenthe intervention groups. Productivity was highest inthe breaks-only group.

A randomized controlled clinical trial wasperformed in van den Heuval’s study. Randomizedcontrolled clinical trials with more than 100participants, including this study by van den Heuvalet al.15), have evidence level I research designs. Theinternal validity of this study was limited tom o d e r a t e b e c a u s e t h e m e a s u r e u s e d f o rmusculoskeletal discomfort has not been provenreliable15, 26).

DISCUSSION

Grades of recommendationThe strength of evidence of each report was

evaluated using the AACPDM method26). Theaggregate strength of each intervention wasevaluated and grades of recommendation weregiven based on the CEBM method27, 28). Strength ofresearch evidence does not equate to interventioneffectiveness.

The aggregate conclusion from the articlesappraised is that exercise decreases musculoskeletaldiscomfort during computer tasks. The overallgrade of recommendation for exercise as anintervention to decrease musculoskeletal discomfortduring computer tasks is a C, because the evidencedoes not present consistent level I or II studies andonly two level V studies are included (Table 6).

Eight articles confirmed the effectiveness ofexercise breaks for reducing musculoskeletaldiscomfort in computer tasks10–12, 14, 15, 31, 38, 39).Only one article, Henning et al., 199712), foundexercise breaks not beneficial for reducingmusculoskeletal discomfort. They found exercisedid decrease musculoskeletal discomfort at a smallwork site, but not at a large worksite. Theparticipants at the large worksite were instructed togive priority to customer inquires over rest/exercisebreaks. Therefore, many breaks may have beenskipped.

Based on the articles appraised in this review, restbreaks are effective at reducing musculoskeletaldiscomfort during computer tasks. The overallgrade of recommendation for rest breaks as anintervention for decreasing musculoskeletal

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discomfort during computer tasks is C because theevidence does not provide consistent level I or IIstudies, and includes only one level V study. Thequality of evidence has improved since 2000 for restbreaks. All studies published since 2000 on theeffect of rest breaks on musculoskeletal discomfortduring computer tasks have levels of evidence of Iand II and have moderate to strong internal validity(Table 7).

Ten articles confirmed the effectiveness of restbreaks in decreasing musculoskeletal discomfort incomputer tasks9–10, 12–13, 15, 33, 37–39). Boucsein andThum32), Sundelin et al.36), and Henning et al.199712) did not find rest breaks effective. Sundelinet al.36) found musculoskeletal discomfort increasedduring all work periods with no difference inmusculoskeletal discomfort between two pausetypes. Boucsein and Thum32) found musculoskeletaldiscomfort increased over the work day and nosignificant differences between two work/restschedules. Henning et al. 199712) found rest breaksdid decrease musculoskeletal discomfort at a smallwork site, but not at a large worksite.

Swanson and Sauter39) found that exercise andrest breaks were equally effective in decreasingstresses of VDT work. Van den Heuval et al.15)

found no additional effects of exercises over restbreaks in recovery of musculoskeletal discomfort.Sundelin and Hagberg38) found no significantdifference in perceived discomfort between passivebreaks, diverting breaks, and exercise breaks.Henning et al. 199712) found exercise breaks weremore effective than passive rest breaks indecreasing musculoskeletal discomfort at a smallwork site but no difference between passive restbreaks and exercise breaks at a large worksite.

Comparison to existing guidelinesThe results of this evidence review on exercise

and rest breaks during computer work are consistentwith the recommendations of the OccupationalSafety and Health Administration (OSHA). OSHAmakes the following recommendations: 1) stretchthe torso, fingers, hands, and arms frequentlythroughout the day; 2) take several short rest breaks;3) stand up and walk for a few minutes periodically;4) alternate computer tasks with non-computer taskswhenever possible; and 5) make small adjustmentsto the desk chair40).

The Official Disability Guidelines Treatment(ODG) in Workers’ Compensation grades thelimited evidence for microbreaks as 2b for workers

Table 7. Level of evidence summary—Rest breaks

Internal validity questions Internal Internalvalidity validity Research Level of

Study 1 2 3 4 5 6 7 sum score* design evidence

Articles concluding rest breaks are beneficial

Balci, 200310) Yes Yes Yes No Yes Yes Yes 6 S II II-SFerreira et al., 199734) Yes Yes Yes No Yes No No 4 M IV IV-MGalinsky et al., 20009) Yes Yes No No Yes No Yes 4 M II II-MHenning et al., 199436) Yes Yes No No Yes No No 3 W IV IV-WHenning et al., 1997 small worksite12) Yes Yes No No Yes No No 3 W II II-WMcLean et al., 200113) Yes Yes Yes No Yes Yes Yes 6 S II II-SSundelin & Hagberg, 198940) Yes Yes Yes No No Yes Yes 5 M IV IV-MSwanson & Sauter, 199241) Yes Yes No No No No Yes 3 W II II-Wvan den Heuval et al., 200315) Yes Yes No No Yes Yes Yes 5 M I I-MZwahlen et al., 198438) Yes Yes No No No Yes No 3 W V V-W

Articles concluding rest breaks are not beneficial

Boucsein & Thum, 199533) Yes Yes No No No No No 2 W IV IV-WHenning et al., 1997 large worksite Yes Yes No No No No No 2 W IV IV-WSundelin et al., 198637) Yes Yes Yes No No Yes Yes 5 M IV IV-M

*S=Strong; M=Moderate; W=Weak31).Grade of Recommendation for Rest Breaks: 27 C.Grade of Recommendation for No Rest Breaks: 27 D.

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with a history of carpal tunnel syndrome. The gradeof 2b represents randomized controlled trials withmoderate quality. ODG recommends 5-minute restbreaks for every 30 minutes of work for computeroperators with a history of neck pathology. TheODG does not recommend specific work-restschedules for any other body regions. The ODGrecommends a maximum of fifteen keystrokes perminute for a maximum of two hours per day forcomputer operators with recent work-relatedmusculoskeletal disorders. Exercise, based on highquality research, is recommended for the treatmentof work related musculoskeletal disorders of alletiologies by guidlelines.gov and ODG. ODG andguidlelines.gov suggest stretching may aid inprevention of low back pain41, 42). The ODGrecommends frequent stretching in cases of carpaltunnel syndrome. However, the ODG andguidelines.gov do not specifically mention briefexercise breaks or workstation exercises duringcomputer work41, 42).

Aggregate limitations on internal validityInternal validity threats were present in all articles

appraised. This was inherent in the dependentvariable being measured. Since musculoskeletald i scomfor t was sub jec t ive ly repor ted byparticipants, the outcome assessor was the subject.Therefore, the outcome assessor could not be blindto intervention status. This lowered the internalvalidity score of all studies by one point. Internalvalidity was low in many field studies because thedropout rate was high. This was mostly due toemployment attrition, not the studies themselves.The internal validity score was lowered one point inevery study in which the dropout rate was 20% orgreater, or if dropout was not reported.

Compliance to the intervention was inconsistentin many of the studies appraised. This may beattributed to employees skipping rest and/orexercise breaks when work demands were high.This weakness is a typical response of employeeswho have mandatory productivity standards2). Inthe study by Henning et al. 1997, computeroperators who worked under an incentive paysystem had increased productivity when rest breaks,or rest breaks with exercise, were added to theirworkday12).

Most of the studies appraised had decreasedinternal validity because the reliability of the toolsused to measure musculoskeletal discomfort was

not presented in the articles. The tools may be validand reliable, but this could not be inferred from thearticles. Another reason for low internal validity inthe reviewed studies was five (33%) of the studiesdid not include power calculations when statisticalsignificance was not found. In those studies theresults should be interpreted with caution since it isunknown if the study had sufficient power to detecta treatment effect. This is a major weaknessthroughout medical literature. In the review ofMoher et al. review of 383 RCT’s published inmedical journals, they found only 32% of the trialswith negative results reported sample sizecalculations43). Halpern’s review found only 42%of studies reported power calculations, and only79% of trials had adequate power to reliably detecta true treatment effect44).

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