nijs.etal04 CFS-INACTIVITY

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Kinesiophobia in Chronic Fatigue Syndrome: Assessment andAssociations With Disability

Jo Nijs, PhD, PT, Kenny De Meirleir, MD, PhD, William Duquet, PhD

ABSTRACT. Nijs J, De Meirleir K, Duquet W. Kinesiophobiain chronic fatigue syndrome: assessment and association with

disability. Arch Phys Med Rehabil 2004;85:1586-92.

Objectives: To investigate aspects of the validity of the totalscores of the Tampa Scale for Kinesiophobia (TSK), DutchVersion, which was modified to make it an appropriate questionnairefor the assessment of kinesiophobia (fear of movement)in chronic fatigue syndrome (CFS) patients (the DutchTSK-CFS), and, using this assessment tool, to examine theassociations between kinesiophobia, exercise capacity, and activitylimitations and participation restrictions in patients withCFS.

Design: Prospective observational studies.

Setting: An outpatient fatigue clinic.

Participants: In the first study, 40 patients fulfilling the1994 US Centers for Disease Control and Prevention (CDC)criteria for CFS were enrolled. The sample of the second studyconsisted of 51 CDC-defined patients with CSF.

Interventions: Not applicable.

Main Outcome Measures: Study 1: Subjects completed aset of questionnaires; the Utrechtse Coping List (UCL), the

Dutch TSK-CFS, and the Dutch Baecke Questionnaire of HabitualPhysical Activity. Study 2: All patients completed 2questionnaires (Chronic Fatigue Syndrome Activities and ParticipationQuestionnaire [CFS-APQ], Dutch TSK-CFS) andperformed a maximal exercise stress test on a bicycle ergometer.The heart rate was monitored continuously by use of anelectrocardiograph. Metabolic and ventilatory parameters weremeasured through spirometry.

Results: Study 1: The Cronbach .coefficient for the individualitem scores on the TSK-CFS was .80. The total scores

on the Dutch TSK-CFS showed a statistically significant correlationwith both the avoidance/abide subscale of the UCL(Spearman .35, P.029) and the total score of the BaeckeQuestionnaire (.45, P.004). Study 2: The total scores onthe Dutch TSK-CFS showed a statistically significant correlationwith the total scores on the CFS-APQ (.39, P.004).No statistically significant associations were observed betweenthe exercise capacity parameters and the total scores on theDutch TSK-CFS.

Conclusions: These results provide evidence for the internalconsistency and the convergent and congruent validity of thescores obtained by use of the Dutch TSK-CFS. Kinesiophobia

appears to be associated with activity limitations/participationrestrictions but not with exercise capacity in patients with CFS.



From the Departments of Human Physiology (Nijs, De Meirleir) and HumanBiometry and Biomechanics (Duquet), Faculty of Physical Education and PhysicalTherapy, Vrije Universiteit Brussel, Brussel, Belgium.

No commercial party having a direct financial interest in the results of the researchsupporting this article has or will confer a benefit upon the authors(s) or upon

anyorganization with which the author(s) is/are associated.

Reprint requests to Jo Nijs, PhD, PT, Vakgroep MFYS/Sportgeneeskunde, AZVUBKRO gebouw 1, Laarbeeklaan 101, 1090 Brussel, Belgium, e-mail:[email protected].

0003-9993/04/8510-8815$30.00/0

doi:10.1016/j.apmr.2003.12.033

Key Words: Avoidance learning; Disabled persons; Fatigue

syndrome, chronic; Fear; Movement; Rehabilitation.

© 2004 by the American Congress of Rehabilitation Medicineand the American Academy of Physical Medicine andRehabilitation

CCHRONIC FATIGUE SYNDROME (CFS) is a chronicdebilitating disease of unknown origin.1 Patients with CFStypically present with debilitating fatigue and a wide variety ofsymptoms. Controversy regarding the etiology and treatment ofCFS continues to affect rehabilitation of patients with CFS.

Patients with CFS typically experience worsening of symptomsafter previously well-tolerated levels of exercise.1,2Fishler et al3 assumed that this may cause avoidance behavior,especially toward fatiguing physical activities such as a maximalexercise stress test. Numerous investigators and clinicianshave speculated that avoidance of activity perpetuates the conditionand hence causes greater disability,4-6 providing part ofthe rationale for incorporating graded exercise and a cognitivebehavioral approach into the management of CFS.7 Disabilityis defined as the inability or restricted ability to performactions, tasks, activities related to required self-care, homemanagement, work, community, and leisure roles in the individual

s

sociocultural context and physical environment.8(pS23)The available evidence points to short-term effectiveness ofcognitive behavioral therapy (often implying graded exercise)for adult patients with CFS.9 Because both cognitive behavioraland graded exercise therapies recommend consistent increasesin physical activity, these therapies focus on decreasing avoidancebehavior toward physical activity. To our knowledge,evidence pointing to the contribution of avoidance behaviortoward physical activity to CFS disability is scarce, with 1report by Fishler.3 Fishler used the nonachievement of 85% ofage-predicted maximal heart rate during incremental exerciseas the sole criterion for avoidance behavior. However, according

to the American College of Sports Medicine, the achievementof age-predicted maximal heart rate shows high intersubjectvariability,10 and we are unaware of experimental evidence



supporting the validity of the nonachievement of 85% of age-predicted maximal heart rate for the assessment of avoidancebehavior toward physical activity. Thus, further investigationregarding the associations between avoidance behavior towardphysical activity, exercise capacity, and CFS disability is warranted.Because we found the content of the Chronic FatigueSyndrome Activities and Participation Questionnaire (CFSAPQ)

reflective of the inability or restricted ability of patientswith CFS to perform actions, tasks, activities related to requiredself-care, home management, work, community, andleisure roles in the individuals sociocultural context and physicalenvironment,11,12 this questionnaire was deemed appropriatefor assessing CFS disability. Moreover, the CFS-APQ is thesole Dutch disease-specific questionnaire for the assessment ofdisability in CFS patients,11 and its psychometric properties arewell characterized.12

Furthermore, many investigators found reduced exercise capacityin patients with CFS,13-15 although this was refuted by

others.16,17 We hypothesized that avoidance behavior toward

Arch Phys Med Rehabil Vol 85, October 2004



KINESIOPHOBIA IN CFS, Nijs

physical activity might prevent patients with CFS from performinga maximal exercise capacity stress test (ie, reachingthe criteria for a maximal performance), especially because themaximal stress test ends when the subject requests to stop the

stress test or when physical or verbal manifestations of severefatigue are present. De Becker et al13 found that only 174 of427 (41%) patients with CFS were able to achieve the targetheart rate (defined as 85% of age-predicted maximal heartrate), compared with 174 of 204 (85%) in the healthy sedentarycontrol group. Likewise, 157 of 427 (37%) patients with CFSattained both requirements for a maximal effort (respiratoryquotient 1.0 and achieving the target heart rate).13 If theperformance on a maximal exercise stress test in patients withCFS is limited by avoidance behavior toward physical activity,then one would expect to find correlations between avoidancebehavior toward physical activity and exercise capacity parameters.

Likewise, we hypothesized that patients with CFS whowere able to perform a maximal exercise stress test (as definedby 2 endpoints: respiratory quotient 1.0 and achieving thetarget heart rate) would have statistically significant lowerscores on the Dutch version of the Tampa Scale for Kinesiophobia(TSK) for CFS (Dutch TSK-CFS), compared with thesubmaximal patients with CFS (those unable to reach therequirements for a maximal effort).

Kinesiophobia, a specific kind of fear-avoidance behavior, isdefined as an excessive, irrational, and debilitating fear ofphysical movement and activity resulting from a feeling ofvulnerability to painful injury or reinjury,18(p36) and it has been

reported as a common feature of patients with CFS, fibromyalgia,and chronic low back pain.19-21 The TSK and the Fear-Avoidance Beliefs Questionnaire22 are 2 available valid questionnairesfor the assessment of fear of movement. However,both measures were constructed to measure pain-related fear ofmovement in pain patients; consequently, these measures maynot be appropriate for the assessment of kinesiophobia inpatients with CFS. In this study, a modified version of the TSKwas used for the assessment of avoidance behavior towardphysical activity. In an attempt to make the TSK appropriatefor patients with CFS, Silver et al21 modified the existing TSKto the TSK-F (fatigue) by changing 11 of the 17 items (pain was replaced by

fatigue

). Fatigue, however, may not be the

major and most debilitating symptom in CFS,23 and patientswith CFS typically present with a wide variety of multisystemsymptoms.1,24 Consequently, modifying the TSK by replacingpain with symptoms may make the TSK a more appropriatequestionnaire for the assessment of kinesiophobia in patientswith CFS. In the first study reported here, the original TSK Dutch Version25 (TSK-DV) was modified for CFS patients(Dutch TSK-CFS), and the internal consistency, as well ascongruent and the convergent validity of the scores obtainedwith this questionnaire, were examined. The Cronbach .reliabilitycoefficient was calculated as a measure for estimating

the internal consistency of the item scores of the questionnaire.The congruent validity of the total scores of the Dutch TSKCFSwith the avoidance/abide subscale of the Utrechtse Coping



List (UCL) was investigated. The convergent validity of theDutch TSK-CFS was tested by examining whether 2 measures,each assessing a distinct indicator of the concept of CFS-associated inactivity, would converge. Therefore, it was hypothesizedthat the total scores obtained with the Dutch TSKCFS(assessing avoidance of activity as an indicator of CFS-associated inactivity) would show a negative correlation with

the scores obtained with the Baecke Questionnaire of HabitualPhysical Activity (assessing habitual physical activity as asecond indicator of the concept of CFS-associated inactivity).

Summarizing the research questions of our report, the primaryaim of these studies was to examine the hypotheticalassociations between avoidance behavior toward physical activity(ie, kinesiophobia), exercise capacity, and disability (assessedby using the Dutch CFS-APQ) in patients with CFS. Iskinesiophobia, assessed by using the Dutch TSK-CFS, relatedto disability in patients with CFS? Are exercise capacity parameters(eg, the percentage of target heart rate achieved and

the duration of the stress test) inversely correlated with kinesiophobia,measured by using the Dutch TSK-CFS? Furthermore,because the Dutch TSK-CFS is a modified version of anexisting, validated questionnaire, our study aimed at examiningwhether the Dutch TSK-CFS is internally consistent, and bothcongruently and convergently valid, when used to assess avoidanceof physical activity in patients with CFS.

METHODS

Study 1

Selection of patients and research design. A total of 44

consecutive patients with a diagnosis of CFS, having Dutch astheir native language and being at least 18 years of age, wererecruited from the Chronic Fatigue Clinic, at Vrije UniversiteitBrussel. To fulfill the US Centers for Disease Control andPrevention (CDC) criteria for CFS,1 clinically evaluated, unexplained,persistent, or relapsing chronic fatigue that is of newor definite onset should result in a substantial reduction inprevious levels of occupational, educational, social, or personalactivities.1 Furthermore, at least 4 of the following symptomsmust have persisted or recurred during 6 or more consecutivemonths and must not have predated the fatigue: impairment inshort-term memory or concentration, tender cervical or axillarylymph nodes, muscle pain, multijoint pain, headache, unrefreshingsleep, and postexertional malaise greater than 24hours.1 Any active medical condition that may explain thepresence of chronic fatigue prohibits the diagnosis of CFS.Hence, all subjects underwent an extensive medical evaluation,consisting of a standard physical examination, medical history,exercise capacity test (ie, to rule out coronary atherosclerosis,exercise-induced hypertension, exercise-induced asthma), androutine laboratory tests. The laboratory tests included a completeblood cell count; determination of the erythrocyte sedimentationrate; serum electrolyte panel; measures of renal,hepatic, and thyroid function; and rheumatic and viral screens.If the patient had a psychiatric problem at the time of disease

onset, then a structured psychiatric interview was performed bya psychiatrist. In a number of cases, further neurologic, gynecologic,endocrine, cardiac, and/or gastrointestinal evaluations



were performed. The medical records were also reviewed todetermine whether patients had organic or psychiatric illnessesthat could explain their symptoms.

An information leaflet was given to all participants, and theywere instructed to read it carefully and, if necessary, to ask foradditional clarification. The information leaflet contained data

addressing the purpose of the study, the nature of the study,patients rights, patients risks and benefits assuming studyparticipation, and the main ethical aspects of the study (eg, thatanonymity was guaranteed). Subjects capable of providingwritten informed consent were then asked to fill out a set ofquestionnaires, starting with the entire UCL (although only theavoidance/abide subscale was used for our study), followed bythe Dutch version of the TSK-CFS and the Dutch BaeckeQuestionnaire. The order in which the patients completed thequestionnaires was arbitrary to standardize the study protocol.The local research ethics committee approved the study.





One woman was excluded because she no longer fulfilled thecurrent CDC definition for CFS at the time the study tookplace; another patient was also excluded because she wasdiagnosed as being mentally disabled and thereby deemed

unable to fill in the questionnaires properly. Two other subjectswere excluded because they failed to complete all questionnairesproperly. Of the remaining 40 patients, 35 were womenand 5 were men. All fulfilled the criteria of Fukuda et al1 forCFS. There was an age range of 19 to 56 years (mean age .standard deviation [SD], 40.29.3y). The mean illness durationwas 108.182.0 months (range, 23 444mo).

Measures. The UCL is a self-administered, Dutch questionnairefor the assessment of different kinds of coping behavior.26 Its psychometric properties are well characterized; ithas been documented to have reliability and validity in a wide

variety of patient populations.27 The UCL consists of 7 sub-scales: active approach, palliative reactions, avoidance/abide,searching for social support, passive coping, expression ofemotions, and using reassuring and comforting thoughts. Forour purposes, only the avoidance/abide subscale was used.Higher scores indicate a higher degree of avoidance and abidingbehavior as a way of dealing with situations or difficulties.For patients recruited from family physicians, the Cronbach .reliability coefficient of the avoidance/abide subscale itemsranged between .67 and .72.28,29 By using a time interval of 4to 5 months, the test-retest reliability coefficient of the avoid-ance/abide UCL subscale scores was .46 in patients recruitedfrom a general health care center.28 Again, for patients recruited

from family physicians, the avoidance/abide subscalescores correlated with the total scores (r .20), and with boththe somatic (r.19) and psychological (r.27) scale scores ofthe Hopkins Symptom Checklist, which indicates that avoidanceis associated with both somatic and psychologic discomfort(substantiating the convergent validity of the scores obtainedwith this UCL subscale).29 The factorial validity of theUCL has been reported,28-30 as well as the predictive validity.30Scoring of the UCL items was performed as described in themanual.27

The Dutch TSK-CFS is a modification of the TSK-DV25;item numbers 2, 4, 7, 8, 10 through 13, and 16 and 17 weremodified by replacing pain by symptoms (items of theDutch TSK-CFS as used in our study are available; appendix 1from the authors contains an English version). The remaining 7items, the instructions, and the scoring system were left unchanged.Each of the items on the questionnaire is providedwith a 4-point Likert scale, with scoring alternatives rangingfrom strongly agree to strongly disagree. A total score iscalculated (14 for each item) after inversion of the individualscores of items 4, 8, 12, and 16. Total scores on the DutchTSK-CFS range between 17 and 68; higher scores indicate ahigher degree of kinesiophobia. A total score greater than 37indicates high fear of movement.21,25

The Baecke Questionnaire is a self-administered questionnairethat assesses habitual leisure and occupational physical



activity.31 This questionnaire consists of 3 sections (work activity,sports activity, nonsports leisure activity), which can becombined into 1 total index. The scoring system is reportedelsewhere; higher scores indicate more habitual physical activity.31 Evidence on its psychometric properties in both healthyand unhealthy subjects has been published.31-33 By using a1-month time interval in healthy men and women, the test-

retest reliability coefficient of the total index of the BaeckeQuestionnaire was .93 (Spearman correlations).34 Spearmancorrelations were counted as well to analyze the associationsbetween the total index of the questionnaire and maximaloxygen consumption (.54, P.05), the percentage of body

fat (.49, P.05), and the 4-week activity history ( .37,P.05).34

Statistical analysis. All data were analyzed by using SPSS,version 10.0,a for Windows. Descriptive statistics (mean, SD,frequencies, percentages, median, interquartile range [IQR])

were used. The Cronbach .coefficient was calculated as ameasure for estimating the internal consistency of the itemscores of the questionnaire. Spearman rank correlation coefficientswere calculated for the analysis of the data, highlightingboth the congruent and convergent validity analysis of theDutch TSK-CFS scores. The significance level was set at .05.

Study 2

Selection of patients and research design. A total of 70consecutive Dutch-speaking patients with chronic fatigue, recruitedfrom the Chronic Fatigue Clinic, Vrije Universiteit

Brussel, were involved in this study. All patients were asked tocomplete 2 questionnaires (first the CFS-APQ,11 then the DutchTSK-CFS), and no additional information was provided, evenwhen patients asked for additional clarification. This way,administrator bias was prevented. The order in which thepatients completed the questionnaires was arbitrary, to standardizethe study protocol. An accompanying letter, explainingthe exact nature and purpose of the research protocol, precededthe questionnaires, and it clearly stipulated that patients werenot obligated to participate and that anonymity was guaranteed.The letter of introduction was followed by standardized sheetsfor the assessment of the demographic features of each patient(age, sex, illness duration). These demographic characteristicswere checked in the patients medical records. After filling inthe questionnaires, patients performed a maximal exercisestress test (see below for a detailed description). The localresearch ethics committee approved the study, and all participantsgave their written informed consent.

Patients not fulfilling the 1994 case definition for CFS1(n5) were excluded from the sample. To establish whetherthe patients fulfilled the 1994 CDC criteria for CFS, the sameprocedure outlined in study 1 was followed. Furthermore, ifpatients were younger than 18 years of age, they were excludedfrom the sample (n2). Because underage patients are thought

to present different activity limitations and participation restrictionswhen compared with adults, use of the CFS-APQ isrestricted to adult patients with CFS.12 In 6 cases, technical



problems (problems with the printer, patients being unable towear the mask) during the exercise testing prevented datacollection. One patient stopped the exercise stress test after 1minute because of hyperventilation and was excluded. Fiveadditional patients were excluded because of incomplete fillingin of the TSK-CFS. Of the remaining 51 patients, 45 (88.2%)were women and 6 were men. Subjects was an age range was

18 to 67 years (mean age .SD, 40.710.0y); mean illnessduration was 86.383.5 months (range, 10 336mo).

Questionnaires. The CFS-APQ is a self-administeredquestionnaire aimed at monitoring activity limitations and participationrestrictions in patients with CFS.11 Its constructionwas based on self-reported activity limitations and participationrestrictions of a large sample of patients with CFS.11 Thescoring system of the CFS-APQ, as described in detail elsewhere,11,12 generates 2 overall scores; the first (CFS-APQ1)uses an importance verification, to acknowledge that people

value things differently; the second total score (CFS-APQ2)does not take this importance verification into account. Thereasoning behind the approach of the importance verification isbased on the assumption that a patient with significant disabilityin activities of importance to areas of his/her life has a lowerquality of life than those who are disabled only for less impor-





tant activities.35 Items are rated on a 4-point Likert-type scale,ranging from 1 (totally not agree) to 4 (totally agree) for thesatisfaction section and 1 (very unimportant) to 4 (very important)for the importance verification. Item scores are calculated

by multiplying the score on the satisfaction part of each questionwith the score on the importance verification (range, 14).The overall scores (CFS-APQ1, CFS-APQ2) were obtained bycounting all item scores and by dividing this sum by theamount of properly completed questions (possible score range,116). A CFS-APQ1 score of 1 indicates no activity limitationsor participation restrictions, whereas 16 represents the maximumscore; for CFS-APQ2 the scores range between 1 and 4.When using the Dutch version of the CFS-APQ in a sample of47 adult patients with CFS, the Cronbach .coefficient was .94and the test-retest reliability coefficients of the overall scores

were .95 or greater (P.001) (time interval, 24h).12 In the samestudy, the overall scores on the CFS-APQ correlated significantlywith visual analog scales (VASs) for pain ( .51,P.001) and fatigue (.50, P.001), substantiating the convergentvalidity of the scores obtained with the Dutch CFSAPQ(both the VASs and CFS-APQ are believed to measure adifferent indicator of the concept of CFS health status).12Additionally, data documenting the content validity of thismeasure in CFS patients have been reported.12 (An English anda French version of the CFS-APQ are available on request fromthe corresponding author.)

The Dutch TSK-CFS aims at monitoring kinesiophobia in

patients with CFS. The construction, scoring system, and someof its psychometric properties are described in study 1.

Exercise testing. Patients performed a bicycle ergometrictest against a graded increase in workload until exhaustion wasreached.13 The exercise tests were performed at a humidity of40% to 60% and at a room temperature of 20° to 22°C.Subjects were asked to take a sitting position on the electromagneticallybraked ergometer,b and after 3 to 5 minutes ofadjustment (aiming at physiologic adjustment to exercise bythe patients) the test was started. Heart rate was monitoredcontinuously at rest (before the adjustment period) and duringexercise. There was continuous recording of the 12-lead electrocardiogramby using an electrocardiograph.c To collect pulmonarydata during the test, an open-circuit spirometerd withautomatic printout every 30 seconds was used. Automatically,averages were attained for peak oxygen consumption(VO2peak) and maximal carbon dioxide production during every30-second interval for the duration of each stage of theexercise. A 2-way breathing valve attached to a mask, whichcovered the patients nose and mouth, was used to collect theexpired air. The air was analyzed continuously for ventilatoryand metabolic variables. Before each test, the spirometer wascalibrated for environmental conditions (ie, the environmentalconditions were known, and the machine was calibrated to

these known values).

A constant increase of 10W/min was chosen to obtain a total



exercise duration between 8 and 12 minutes, which is suggestedas being an optimal test period.36 To avoid early onset offatigue in the lower extremities because of inadequate physicalfitness, the duration of the exercise was kept below 15 minutes.All subjects started the test at 10W/min, with an increase of10W/min.13

The following parameters were obtained: heart rate at rest(HRrest), peak heart rate (HRpeak), exercise duration, maximalwork capacity attained, VO2peak, VO2peak per kilogram ofbody weight, functional aerobic impairment, peak respiratoryquotient (RQpeak), and the percentage of target heart rateachieved (%THR). The age-predicted HRpeak was calculatedas 220 minus the subjects age in years.37 The metabolic data

analyzed were the means of the last 30 seconds from the finalstage (ie, the values measured over the last 30 seconds for eachsubject were averaged to obtain a 30-second mean) of exerciseor the highest value attained if a decline in VO2 occurred at the

final workload.13 Functional aerobic impairment is the percentagedifference between observed VO2peak and the VO2peakpredicted for a healthy person of the same age, gender, andhabitual activity status.38 VO2peak for any age can be predictedby using the regression equations from reference 38; for thepurpose of our study, we used the equations for sedentaryindividuals.

Exercise capacity testing is widely used for the disabilityassessment of patients with CFS, and it appears to be bothreproducible and valid.39,40 The bicycle stress testing protocolused in our study was able to distinguish between female CFSpatients and healthy sedentary females.13

Statistical analysis. All data were entered into MicrosoftExcel 2000e and then analyzed by using SPSS, version 10.0,afor Windows. Appropriate descriptive statistics (mean, SD,frequencies, percentages, median, IQR) were used. Again, theCronbach .coefficient was calculated as a measure for estimatingthe internal consistency of the item scores of the questionnaire.Correlations between the scores obtained with theDutch TSK-CFS and the disability parameters (CFS-APQ,exercise capacity) were assessed by using the Spearman rankcorrelation coefficient. Because it is well established thatwomen have a lower maximal oxygen uptake than men, poolingof gender data may bias the results.16 The dataset wastherefore reanalyzed by excluding all men. The significancelevel was set at .01, to help protect against potential type Ierrors. Finally, patients were divided into 2 groups, based ontheir ability to perform a maximal effort during the exercisetesting (defined by 2 endpoints: RQpeak 1.0 and an age-predicted target heart rate of at least 85%13). This was done toexamine whether patients with CFS capable of performing amaximal effort have less kinesiophobia than those incapable ofattaining the requirements for a maximal effort. The differencesbetween these 2 groups were assessed by using theLevene test for equality of variances, Student t test (independent

samples t test, 2-tailed for illness duration and age), Fisherexact test (gender), and independent samples nonparametricMann-Whitney U test (2-tailed for the scores obtained with the



Dutch TSK-CFS). Before entering the Student t test analysis,the 1-sample Kolmogorov-Smirnov goodness-of-fit test wasused to examine whether the age and illness duration of bothgroups were normally distributed. The level of significance wasset at .05.

RESULTS

Study 1

The Dutch TSK-CFS scores ranged between 24 and 54; themedian was 40 and the IQR was 11.8. Twenty-five of the 40patients (62.5%) attained a Dutch TSK-CFS total score greaterthan 37, indicating high fear of movement.21,25 For the avoid-ance/abide subscale of the UCL, the median score and IQRwere 9 and 3, respectively, (range, 4 13). The total scores onthe Baecke Questionnaire ranged between 4 and 9 (median7.13, IQR1.37). The Cronbach .coefficient for the

individual item scores on the TSK-CFS was .80. The totalscores on the Dutch TSK-CFS showed a statistically significantcorrelation with the UCL avoidance/abide subscale ( .35,P.029) and the Baecke Questionnaire total score ( .45,P.004).





Table 1: Descriptive Data of the Dutch TSK-CFS andthe Disability Assessment (n51)

Questionnaires Median IQR Range

Dutch TSK-CFS* 42.0 10.0 30.055.0CFS-APQ1 8.6 3.7 4.415.1CFS-APQ2 2.8 1.0 1.53.8Exercise Capacity Parameter Mean .SD RangeExercise duration (min) 9.73.0 4.418.2HRrest (bpm) 86.615.4 54.0133.0HRpeak (bpm) 149.322.4 102.0197.0Workload (W) 94.030.4 40.0160.0Workload per body weight (w/kg) 1.40.4 0.62.9VO2peak (L/min) 1196.8368.7 600.02099.0VO2peak/body weight

(mLkg1min1) 17.15.9 6.631.8% functional aerobic impairment 39.921.2 7.9 to 77.4RQpeak 1.10.1 0.91.4%THR 83.512.2 58.0112.0

*Total scores on the Dutch TSK-CFS range between 17 and 68;higher scores indicate a higher degree of kinesiophobia.

A CFS-APQ1 score of 1 indicates no activity limitations or participationrestrictions; 16 represents the maximum score.The CFS-APQ2 scores range between 1 and 4.Study 2

The Dutch TSK-CFS scores ranged between 30 and 55; themedian score was 42 and the IQR was 10.0. Thirty-five of the51 patients (68.6%) attained a Dutch TSK-CFS total scoregreater than 37, indicating high fear of movement.21,25 Accordingto the exercise capacity data, the minority of the subjects(n16; 31.4%) had no functional impairment (functional aerobicimpairment 27%38). Eight patients with CFS (15.7%)showed evidence of mild functional aerobic impairment (functionalaerobic impairment, 27% 40%), whereas the remaining27 (52.9%) had moderate to marked functional aerobic impairment.By using the American Medical Association Guidelinesfor Impairment Rating,41 4 patients (7.8%) were classified ashaving

no impairment of the whole person

(VO2peak/body

weight, 25mLkg1min1), and 11 (21.6%) had mild impairmentof the whole person. The majority of the sample(n36; 70.6%) corresponded to class 3 or 4, suggestive ofmoderate to severe impairment of the whole person (VO2peak/body weight, 15mLkg1min1). All descriptivedata of the disability assessment are in table 1.

The Cronbach .for the individual item scores on the TSKCFSwas .74. The Dutch TSK-CFS total scores showed astatistically significant correlation to both total scores on theCFS-APQ (.39, P.004 for CFS-APQ1; .44, P .001 for

CFS-APQ2). No statistically significant associations were observedbetween the exercise capacity parameters and the totalscores of the Dutch TSK-CFS (table 2). Analyzing only the



data from the women (n45) did not change the outcome:again no statistically significant associations were observed forany of the exercise capacity parameters (data not shown).When patients who did not perform a maximal exercise capacitytest (n24; Dutch TSK-CFS median41.0; IQR 10.0)were compared with the maximal group (n27; median43.0;IQR10.0), no statistically significant differences in the total

scores obtained with the Dutch TSK-CFS were observed(Mann-Whitney U302.0, z.166, P.868). Comparing thedemographic features (age, illness duration, sex distribution)between the 2 groups showed no statistically significant differences(data not shown).

DISCUSSION

Study 1

In study 1, the counted Cronbach .coefficient was .80,

indicating sufficient internal consistency of the item scores ofthe Dutch TSK-CFS.42 The Cronbach .was slightly lower instudy 2 (.74). Because the Dutch TSK-CFS total scores showeda statistically significant correlation with the UCL avoidance/abide subscale scores, evidence for the congruent validity ofthe Dutch TSK-CFS total scores was provided. The convergentvalidity of the scores obtained with the Dutch TSK-CFS (assessingavoidance of activity as an indicator of CFS-associatedinactivity) was supported by the observed statistically significantinverse correlation with the overall scores of the BaeckeQuestionnaire (assessing habitual physical activity as a secondindicator of the concept of CFS-associated inactivity). Still, the

test-retest reliability and some aspects of the validity (eg,criterion validity) of the scores obtained with the Dutch TSKCFSremain to be established. No data are currently availableto validate the English version of the TSK-CFS (appendix 1).

Study 2

At least a subset of patients with CFS can be characterizedby avoidance of physical activity as a coping strategy.43 Byusing the cutoff point of 37,21,25 the prevalence of kinesiophobiaamong the patients with CSF examined in studies 1 and 2was 60 out of 91 (65%). These data provide evidence for a highprevalence of kinesiophobia among adult patients with CSFwho seek treatment for their complaints. Because our samplewas not randomly selected from the CFS community, we areunable to extrapolate these results to the entire CFS population.This prevalence rate was considerably higher than that reportedby Silver et al21 (15/33, 45.5%). However, this might beexplained by the high number of tertiary referrals seen in ourspecialized chronic fatigue clinic.

Numerous investigators and clinicians have speculated thatavoidance behavior toward physical activity may actually bemaladaptive and cause a greater burden in patients with CFS.4-6This view is partly supported by the present report; a strong

association between kinesiophobia and self-reported activitylimitations and participation restrictions was observed ( .39,




P.004 for CFS-APQ1; .44, P.001 for CFS-APQ2). Becausethe CFS-APQ also queries social interactions, theseresults are in accordance with the Heijmans study,5 whichfound cognitive-avoidant coping to be negatively related to

social functioning (R.26, P.01). To our knowledge, oursis the first report addressing the association among fear ofmovement (kinesiophobia), a specific kind of fear-avoidancebehavior, and disability in patients with CFS. Still, long-termfollow-up studies are required to establish a causal relationshipbetween kinesiophobia and daily functioning.

The exercise capacity data confirmed earlier reports thatprovide evidence for a reduced exercise capacity in patientswith CSF.13-15 We hypothesized that avoidance behavior towardphysical activity might prevent patients with CSF fromperforming a maximal exercise capacity stress test (ie, reaching

the criteria for a maximal performance). We did not, however,find that exercise capacity parameters (eg, the percentage oftarget heart rate achieved and the duration of the stress test)were inversely correlated with kinesiophobia, at least not inthis consecutively allocated sample of patients with CSF. Inaddition, when comparing patients who did not perform amaximal exercise capacity test with the maximal group, nostatistically significant differences in the total scores obtainedwith the Dutch TSK-CFS were found. Thus, it appears thatexercise capacity and kinesiophobia are unrelated in adultpatients with CFS who seek treatment for their symptoms.These results are in accordance with the Silver study,21 whichfound no association between kinesiophobia and the maximal

heart rate or the resting heart rate in patients with CFS. Silverdid not collect metabolic or ventilatory parameters.

When interpreting these results as they apply to the practiceof physical therapy and rehabilitation medicine, we suggestusing the Dutch TSK-CFS for the assessment of kinesiophobiain patients with CFS. Furthermore, because evidence substantiatingthe clinical importance of kinesiophobia in patients withCSF was provided (ie, the associations between the kinesiophobiaand activity limitations and participation restrictions),kinesiophobia should become the focus of management strategiesat least in those patients with CSF presenting with highfear of movement. Graded exercise therapy and cognitive behavioraltherapy have been suggested as strategies to reduceavoidance behavior toward physical activity in CFS patients.7However, a recent study44 explored whether exercise induces asignificantly greater complement activation (an important componentof the immune system) in persons with CFS than inhealthy controls. Among the patients with CSF studied, thecomplement activation was significantly associated with apostexercise increase in symptom severity.44 This, togetherwith the results of a treatment audit among British CFS patients,showing that 50% of all patients who had tried gradedexercise reported that this had worsened their condition,45might motivate CFS practitioners and researchers to search for

other therapies capable of reducing kinesiophobia in CFS patients.To reduce kinesiophobia without using graded exercisetherapy, patients with CFS might benefit from exposure in vivo



to a set of individually tailored, fear eliciting physical movements.This treatment approach has been described by Vlaeyenet al,46 but its effectiveness in patients with CSF has yet to beestablished.

These results should be interpreted with some caution. First,because a number of exercise capacity parameters were collected

in study 2, multiple statistical tests were performed. Tohelp protect against potential type I errors, the significancelevel was set at .01. Second, the study design did not allow usto draw conclusions about causality. Third, no data document

ing the test-retest reliability of the Dutch TSK-CFS are currentlyavailable.

CONCLUSIONS

The results of study 1 substantiate the internal consistency

and the congruent and the convergent validity of the scoresobtained with the Dutch TSK-CFS. The data presented in study2 suggest that kinesiophobia and activity limitations and participationrestrictions are related in adult patients with CFSwho seek treatment for their symptoms. There appears to be noassociation between exercise capacity and kinesiophobia inadult patients with CFS who seek treatment for their symptoms.More work is needed to examine the causal relationshipbetween kinesiophobia and activity limitations and participationrestrictions, as well as to explain the reduced exercisecapacity in patients with CFS.

Acknowledgments: We thank Lieve De Hauwere (GFN) for her

help during the exercise capacity stress testing, and Katrien Vanherberghen,PT, for editing the final version of the manuscript. We aregrateful to Elke Van Hoof, PhD, for assisting in the scoring of the UCLand for critical review of the study proposal.

APPENDIX 1: THE ITEMS OF THE TSK-CFSVERSION IN ENGLISH

1. I am afraid that I might injure myself if I exercise.2. If I were to try to overcome it, my symptoms wouldincrease.3. My body is telling me I have something dangerouslywrong.4. My symptoms would probably be relieved if I were toexercise.5. People are not taking my medical condition seriouslyenough.6. My illness has put my body at risk for the rest of my life.7. My symptoms always mean I have harmed my body.8. Just because something aggravates my symptoms does notmean it is dangerous.9. I am afraid that I might injure myself accidentally.10. Simply being careful that I do not make any unnecessarymovements is the safest thing I can do to prevent my symptoms

from worsening.11. I would not have this many symptoms if there was notsomething potentially dangerous going on in my body.




fatigue syndrome: association with disability, somatization andpsychopathology. J Psychosom Res 1997;42:369-78.

4. Van Houdenhove B. Chronische pijn, chronische vermoeidheid:

een indicatie voor psychosomatische revalidatie. TijdschrGeneeskd 1996;52:1371-8.5. Heijmans MJ. Coping and adaptive outcome in chronic fatiguesyndrome: importance of illness cognitions. J Psychosom Res1998;45:39-51.6. Ray C, Jefferies S, Weir WR. Coping and other predictors ofoutcome in chronic fatigue syndrome: a 1-year follow-up. J PsychosomRes 1997;43:405-15.7. Powell P, Bentall RP, Nye FJ, Edwards RH. Randomised controlledtrial of patient education to encourage graded exercise inchronic fatigue syndrome. BMJ 2001;322:1-5.8. American Physical Therapy Association. Guide to physical therapist

practice. Phys Ther 2001;81:S19-25.9. Price JR, Couper J. Cognitive behaviour therapy for adults withchronic fatigue syndrome. Cochrane Database Syst Rev 2000;(2):CD001027.10. Franklin B, Whaley MH, Howley ET. ACSMs guidelines forexercise testing and prescription. 6th ed. Philadelphia: LippincottWilliams & Wilkins; 2000. p 117.11. Nijs J, Vaes P, Van Hoof E, De Becker P, McGregor N, DeMeirleir K. Activity limitations and participation restrictions inpatients with chronic fatigue syndromeconstruction of a diseasespecific questionnaire. J Chronic Fatigue Syndr 2002;10:3-23.12. Nijs J, Vaes P, McGregor N, Van Hoof E, De Meirleir K. Psychometricproperties of the Dutch Chronic Fatigue Syndrome

Activities and Participation Questionnaire (CFS-APQ). Phys Ther2003;83:444-54.13. De Becker P, Roeykens J, Reynders M, McGregor N, De MeirleirK. Exercise capacity in chronic fatigue syndrome. Arch InternMed 2000;160:3270-7.14. Riley MS, OBrien CJ, McCluskey DR, Bell NP, Nicholls DP.Aerobic work capacity in patients with chronic fatigue syndrome.BMJ 1990;301:953-6.15. Sisto SA, LaManca J, Cordero DL, et al. Metabolic and cardiovasculareffects of a progressive exercise test in patients withchronic fatigue syndrome. Am J Med 1996;100:634-40.16. Sargent C, Scroop GC, Nemeth PM, Burnet RB, Buckley JD.Maximal oxygen uptake and lactate metabolism are normal inchronic fatigue syndrome. Med Sci Sports Exerc 2002;34:51-6.17. Kent-Braun JA, Sharma KR, Weiner MW, Massie B, Miller RG.Central basis of muscle fatigue in chronic fatigue syndrome.Neurology 1993;43:125-31. Comment in: Neurology 1993;43:1866-7.18. Kori SH, Miller RP, Todd DD. Kinesiophobia: a new view ofchronic pain behavior. Pain Manage 1990;Jan/Feb:35-43.19. Goubert L, Crombez G, Vlaeyen J, Van Damme S, Van denBroeck A, Van Houdenhove B. De Tampa schaal voor Kinesiofobie:psychometrische karakteristieken en normering. GedragGezondheid 2000;28:54-62.20. Vlaeyen JW, Kole-Snijders AM, Rotteveel AM, Ruesink R, Heuts

P. The role of fear of movement/(re)injury in pain disability. JOccup Rehabil 1995;5:235-52.21. Silver A, Haeney M, Vijayadurai P, Wilks D, Pattrick M, Main



J Chronic Fatigue Syndr 1997;3:5-7.41. Make B, Jones JF. Impairment of patients with Chronic FatigueSyndrome. J Chronic Fatigue Syndr 1997;3:43-55.42. Dijkers MP, Kropp GC, Esper RM, Yavuzer G, Cullen N, BakdaliehY. Reporting on reliability and validity of outcome measuresin medical rehabilitation research. Disabil Rehabil 2002;24:819-27.

43. Afari N, Schmaling KB, Herrell R, Hartman S, Goldberg J,Buchwald DS. Coping strategies in twins with chronic fatigue andchronic fatigue syndrome. J Psychosom Res 2000;48:547-54.44. Sorensen B, Streib JE, Strand M, et al. Complement activation ina model of chronic fatigue syndrome. J Allergy Clin Immunol2003;112:397-403.45. Shephard C. Pacing and exercise in chronic fatigue syndrome.Physiotherapy 2001;87:395-6.46. Vlaeyen JW, de Jong J, Geilen M, Heuts PH, van Breukelen G.The treatment of fear of movement/(re)injury in chronic low backpain: further evidence on the effectiveness of exposure in vivo.Clin J Pain 2002;18:251-61.

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a. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.b. Jaeger 900; Lode BV, Zernikepark 16, 9747 AN Groningen, TheNetherlands.c. GE Medical Systems, Milwaukee, WI.d. Mijnhart Oxycon; IBM, Bunnik, the Netherlands.e. Microsoft Corp, One Microsoft Wy, Redmond, WA 98052.Arch Phys Med Rehabil Vol 85, October 2004

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