Source: Archive Physical Medicine Rehabilitation Vol 85, #10, 1586-1592 Date: October 2004 URL: http://www2.archives-pmr.org/scripts/om.dll/serve?action=searchDB&searchDBfor=home&id=apmr Kinesiophobia in Chronic Fatigue Syndrome: Assessment and Associations With Disability --------------------------------------------------------------------------- Jo Nijs, PhD, PT, Kenny De Meirleir, MD, PhD, William Duquet, PhD >From the Departments of Human Physiology (Nijs, De Meirleir) and Human Biometry and Biomechanics (Duquet), Faculty of Physical Education and Physical Therapy, Vrije Universiteit Brussel, Brussel, Belgium. No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors(s) or upon any organization with which the author(s) is/are associated. Reprint requests to Jo Nijs, PhD, PT, Vakgroep MFYS/Sportgeneeskunde, AZ-VUB KRO gebouw 1, Laarbeeklaan 101, 1090 Brussel, Belgium, e-mail: Jo.Nijs@vub.ac.be. 0003-9993/04/8510-8815$30.00/0 doi: 10.1016/j.apmr.2003.12.033 ABSTRACT Nijs J, De Meirleir K, Duquet W. Kinesiophobia in 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 total scores of the Tampa Scale for Kinesiophobia (TSK), Dutch Version, which was modified to make it an appropriate questionnaire for the assessment of kinesiophobia (fear of movement) in chronic fatigue syndrome (CFS) patients (the Dutch TSK-CFS), and, using this assessment tool, to examine the associations between kinesiophobia, exercise capacity, and activity limitations and participation restrictions in patients with CFS. Design: Prospective observational studies. Setting: An outpatient fatigue clinic. Participants: In the first study, 40 patients fulfilling the 1994 US Centers for Disease Control and Prevention (CDC) criteria for CFS were enrolled. The sample of the second study consisted of 51 CDC-defined patients with CSF. Interventions: Not applicable. Main Outcome Measures: Study 1: Subjects completed a set of questionnaires; the Utrechtse Coping List (UCL), the Dutch TSK-CFS, and the Dutch Baecke Questionnaire of Habitual Physical Activity. Study 2: All patients completed 2 questionnaires (Chronic Fatigue Syndrome Activities and Participation Questionnaire [CFS-APQ], Dutch TSK-CFS) and performed a maximal exercise stress test on a bicycle ergometer. The heart rate was monitored continuously by use of an electrocardiograph. Metabolic and ventilatory parameters were measured through spirometry. Results: Study 1: The Cronbach alpha coefficient for the individual item scores on the TSK-CFS was .80. The total scores on the Dutch TSK-CFS showed a statistically significant correlation with both the avoidance/abide subscale of the UCL (Spearman rho=.35, P=.029) and the total score of the Baecke Questionnaire (rho=.45, P=.004). Study 2: The total scores on the Dutch TSK-CFS showed a statistically significant correlation with the total scores on the CFS-APQ (rho=.39, P=.004). No statistically significant associations were observed between the exercise capacity parameters and the total scores on the Dutch TSK-CFS. Conclusions: These results provide evidence for the internal consistency and the convergent and congruent validity of the scores obtained by use of the Dutch TSK-CFS. Kinesiophobia appears to be associated with activity limitations/participation restrictions but not with exercise capacity in patients with CFS. Key Words: Avoidance learning; Disabled persons; Fatigue syndrome, chronic; Fear; Movement; Rehabilitation. CHRONIC FATIGUE SYNDROME (CFS) is a chronic debilitating disease of unknown origin. 1 Patients with CFS typically present with debilitating fatigue and a wide variety of symptoms. Controversy regarding the etiology and treatment of CFS continues to affect rehabilitation of patients with CFS. Patients with CFS typically experience worsening of symptoms after previously well-tolerated levels of exercise. 1,2 Fishler et al 3 assumed that this may cause avoidance behavior, especially toward fatiguing physical activities such as a maximal exercise stress test. Numerous investigators and clinicians have speculated that avoidance of activity perpetuates the condition and hence causes greater disability, 4-6 providing part of the rationale for incorporating graded exercise and a cognitive behavioral approach into the management of CFS. 7 Disability is defined as "the inability or restricted ability to perform actions, tasks, activities related to required self-care, home management, work, community, and leisure roles in the individual's sociocultural context and physical environment." 8(pS23) The available evidence points to short-term effectiveness of cognitive behavioral therapy (often implying graded exercise) for adult patients with CFS. 9 Because both cognitive behavioral and graded exercise therapies recommend consistent increases in physical activity, these therapies focus on decreasing avoidance behavior toward physical activity. To our knowledge, evidence pointing to the contribution of avoidance behavior toward physical activity to CFS disability is scarce, with 1 report by Fishler. 3 Fishler used the nonachievement of 85% of age-predicted maximal heart rate during incremental exercise as the sole criterion for avoidance behavior. However, according to the American College of Sports Medicine, the achievement of age-predicted maximal heart rate shows high intersubject variability, 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 avoidance behavior toward physical activity. Thus, further investigation regarding the associations between avoidance behavior toward physical activity, exercise capacity, and CFS disability is warranted. Because we found the content of the Chronic Fatigue Syndrome Activities and Participation Questionnaire (CFS-APQ) reflective of the inability or restricted ability of patients with CFS to perform actions, tasks, activities related to required self-care, home management, work, community, and leisure roles in the individual's sociocultural context and physical environment, 11,12 this questionnaire was deemed appropriate for assessing CFS disability. Moreover, the CFS-APQ is the sole Dutch disease-specific questionnaire for the assessment of disability in CFS patients, 11 and its psychometric properties are well characterized. 12 Furthermore, many investigators found reduced exercise capacity in patients with CFS, 13-15 although this was refuted by others. 16,17 We hypothesized that avoidance behavior toward physical activity might prevent patients with CFS from performing a maximal exercise capacity stress test (ie, reaching the criteria for a maximal performance), especially because the maximal stress test ends when the subject requests to stop the stress test or when physical or verbal manifestations of severe fatigue are present. De Becker et al 13 found that only 174 of 427 (41%) patients with CFS were able to achieve the target heart rate (defined as 85% of age-predicted maximal heart rate), compared with 174 of 204 (85%) in the healthy sedentary control group. Likewise, 157 of 427 (37%) patients with CFS attained both requirements for a maximal effort (respiratory quotient 1.0 and achieving the target heart rate). 13 If the performance on a maximal exercise stress test in patients with CFS is limited by avoidance behavior toward physical activity, then one would expect to find correlations between avoidance behavior toward physical activity and exercise capacity parameters. Likewise, we hypothesized that patients with CFS who were able to perform a maximal exercise stress test (as defined by 2 endpoints: respiratory quotient 1.0 and achieving the target heart rate) would have statistically significant lower scores on the Dutch version of the Tampa Scale for Kinesiophobia (TSK) for CFS (Dutch TSK-CFS), compared with the submaximal patients with CFS (those unable to reach the requirements for a maximal effort). Kinesiophobia, a specific kind of fear-avoidance behavior, is defined as "an excessive, irrational, and debilitating fear of physical movement and activity resulting from a feeling of vulnerability 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 Questionnaire 22 are 2 available valid questionnaires for the assessment of fear of movement. However, both measures were constructed to measure pain-related fear of movement in pain patients; consequently, these measures may not be appropriate for the assessment of kinesiophobia in patients with CFS. In this study, a modified version of the TSK was used for the assessment of avoidance behavior toward physical activity. In an attempt to make the TSK appropriate for patients with CFS, Silver et al 21 modified the existing TSK to 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 patients with CFS typically present with a wide variety of multisystem symptoms. 1,24 Consequently, modifying the TSK by replacing pain with symptoms may make the TSK a more appropriate questionnaire for the assessment of kinesiophobia in patients with CFS. In the first study reported here, the original TSK - Dutch Version 25 (TSK-DV) was modified for CFS patients (Dutch TSK-CFS), and the internal consistency, as well as congruent and the convergent validity of the scores obtained with this questionnaire, were examined. The Cronbach alpha reliability coefficient 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 TSK-CFS with the avoidance/abide subscale of the Utrechtse Coping List (UCL) was investigated. The convergent validity of the Dutch 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 hypothesized that the total scores obtained with the Dutch TSK-CFS (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 Habitual Physical Activity (assessing habitual physical activity as a second indicator of the concept of CFS-associated inactivity). Summarizing the research questions of our report, the primary aim of these studies was to examine the hypothetical associations between avoidance behavior toward physical activity (ie, kinesiophobia), exercise capacity, and disability (assessed by using the Dutch CFS-APQ) in patients with CFS. Is kinesiophobia, assessed by using the Dutch TSK-CFS, related to 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 an existing, validated questionnaire, our study aimed at examining whether the Dutch TSK-CFS is internally consistent, and both congruently and convergently valid, when used to assess avoidance of 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 as their native language and being at least 18 years of age, were recruited from the Chronic Fatigue Clinic, at Vrije Universiteit Brussel. To fulfill the US Centers for Disease Control and Prevention (CDC) criteria for CFS, 1 clinically evaluated, unexplained, persistent, or relapsing chronic fatigue that is of new or definite onset should result in a substantial reduction in previous levels of occupational, educational, social, or personal activities. 1 Furthermore, at least 4 of the following symptoms must have persisted or recurred during 6 or more consecutive months and must not have predated the fatigue: impairment in short-term memory or concentration, tender cervical or axillary lymph nodes, muscle pain, multijoint pain, headache, unrefreshing sleep, and postexertional malaise greater than 24 hours. 1 Any active medical condition that may explain the presence 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), and routine laboratory tests. The laboratory tests included a complete blood cell count; determination of the erythrocyte sedimentation rate; 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 by a psychiatrist. In a number of cases, further neurologic, gynecologic, endocrine, cardiac, and/or gastrointestinal evaluations were performed. The medical records were also reviewed to determine whether patients had organic or psychiatric illnesses that could explain their symptoms. An information leaflet was given to all participants, and they were instructed to read it carefully and, if necessary, to ask for additional clarification. The information leaflet contained data addressing the purpose of the study, the nature of the study, patients' rights, patients' risks and benefits assuming study participation, and the main ethical aspects of the study (eg, that anonymity was guaranteed). Subjects capable of providing written informed consent were then asked to fill out a set of questionnaires, starting with the entire UCL (although only the avoidance/ abide subscale was used for our study), followed by the Dutch version of the TSK-CFS and the Dutch Baecke Questionnaire. The order in which the patients completed the questionnaires was arbitrary to standardize the study protocol. The local research ethics committee approved the study. One woman was excluded because she no longer fulfilled the current CDC definition for CFS at the time the study took place; another patient was also excluded because she was diagnosed as being mentally disabled and thereby deemed unable to fill in the questionnaires properly. Two other subjects were excluded because they failed to complete all questionnaires properly. Of the remaining 40 patients, 35 were women and 5 were men. All fulfilled the criteria of Fukuda et al 1 for CFS. There was an age range of 19 to 56 years (mean age standard deviation [SD], 40.2 p/m 9.3 y). The mean illness duration was 108.1 p/m 82.0 months (range, 23-444 mo). Measures. The UCL is a self-administered, Dutch questionnaire for the assessment of different kinds of coping behavior. 26 Its psychometric properties are well characterized; it has been documented to have reliability and validity in a wide variety of patient populations. 27 The UCL consists of 7 subscales: active approach, palliative reactions, avoidance/abide, searching for social support, passive coping, expression of emotions, and using reassuring and comforting thoughts. For our purposes, only the avoidance/abide subscale was used. Higher scores indicate a higher degree of avoidance and abiding behavior as a way of dealing with situations or difficulties. For patients recruited from family physicians, the Cronbach alpha reliability coefficient of the avoidance/abide subscale items ranged between .67 and .72. 28,29 By using a time interval of 4 to 5 months, the test-retest reliability coefficient of the avoidance/ abide UCL subscale scores was .46 in patients recruited from a general health care center. 28 Again, for patients recruited from family physicians, the avoidance/abide subscale scores correlated with the total scores (r=.20), and with both the somatic (r=.19) and psychological (r=.27) scale scores of the Hopkins Symptom Checklist, which indicates that avoidance is associated with both somatic and psychologic discomfort (substantiating the convergent validity of the scores obtained with this UCL subscale). 29 The factorial validity of the UCL has been reported, 28-30 as well as the predictive validity. 30 Scoring of the UCL items was performed as described in the manual. 27 The Dutch TSK-CFS is a modification of the TSK-DV 25 ; item numbers 2, 4, 7, 8, 10 through 13, and 16 and 17 were modified by replacing "pain" by "symptoms" (items of the Dutch TSK-CFS as used in our study are available; appendix 1 from the authors contains an English version). The remaining 7 items, the instructions, and the scoring system were left unchanged. Each of the items on the questionnaire is provided with a 4-point Likert scale, with scoring alternatives ranging from "strongly agree" to "strongly disagree." A total score is calculated (1-4 for each item) after inversion of the individual scores of items 4, 8, 12, and 16. Total scores on the Dutch TSK-CFS range between 17 and 68; higher scores indicate a higher degree of kinesiophobia. A total score greater than 37 indicates high fear of movement. 21,25 The Baecke Questionnaire is a self-administered questionnaire that assesses habitual leisure and occupational physical activity. 31 This questionnaire consists of 3 sections (work activity, sports activity, nonsports leisure activity), which can be combined into 1 total index. The scoring system is reported elsewhere; higher scores indicate more habitual physical activity. 31 Evidence on its psychometric properties in both healthy and unhealthy subjects has been published. 31-33 By using a 1-month time interval in healthy men and women, the test-retest reliability coefficient of the total index of the Baecke Questionnaire was .93 (Spearman correlations). 34 Spearman correlations were counted as well to analyze the associations between the total index of the questionnaire and maximal oxygen consumption (rho=.54, P<.05), the percentage of body fat (rhp=.49, P=.05), and the 4-week activity history (rho=.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 alpha coefficient was calculated as a measure for estimating the internal consistency of the item scores of the questionnaire. Spearman rank correlation coefficients were calculated for the analysis of the data, highlighting both the congruent and convergent validity analysis of the Dutch TSK-CFS scores. The significance level was set at .05. Study 2 Selection of patients and research design. A total of 70 consecutive Dutch-speaking patients with chronic fatigue, recruited from the Chronic Fatigue Clinic, Vrije Universiteit Brussel, were involved in this study. All patients were asked to complete 2 questionnaires (first the CFS-APQ, 11 then the Dutch TSK-CFS), and no additional information was provided, even when patients asked for additional clarification. This way, administrator bias was prevented. The order in which the patients completed the questionnaires was arbitrary, to standardize the study protocol. An accompanying letter, explaining the exact nature and purpose of the research protocol, preceded the questionnaires, and it clearly stipulated that patients were not obligated to participate and that anonymity was guaranteed. The letter of introduction was followed by standardized sheets for the assessment of the demographic features of each patient (age, sex, illness duration). These demographic characteristics were checked in the patient's medical records. After filling in the questionnaires, patients performed a maximal exercise stress test (see below for a detailed description). The local research ethics committee approved the study, and all participants gave their written informed consent. Patients not fulfilling the 1994 case definition for CFS 1 (n=5) were excluded from the sample. To establish whether the patients fulfilled the 1994 CDC criteria for CFS, the same procedure outlined in study 1 was followed. Furthermore, if patients were younger than 18 years of age, they were excluded from the sample (n=2). Because underage patients are thought to present different activity limitations and participation restrictions when compared with adults, use of the CFS-APQ is restricted to adult patients with CFS. 12 In 6 cases, technical problems (problems with the printer, patients being unable to wear the mask) during the exercise testing prevented data collection. One patient stopped the exercise stress test after 1 minute because of hyperventilation and was excluded. Five additional patients were excluded because of incomplete filling in 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 p/m SD, 40.7 p/m 10.0 y); mean illness duration was 86.3 p/m 83.5 months (range, 10-336 mo). Questionnaires. The CFS-APQ is a self-administered questionnaire aimed at monitoring activity limitations and participation restrictions in patients with CFS. 11 Its construction was based on self-reported activity limitations and participation restrictions of a large sample of patients with CFS. 11 The scoring 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. The reasoning behind the approach of the importance verification is based on the assumption that a patient with significant disability in activities of importance to areas of his/her life has a lower quality of life than those who are disabled only for less important activities. 35 Items are rated on a 4-point Likert-type scale, ranging from 1 (totally not agree) to 4 (totally agree) for the satisfaction 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 question with the score on the importance verification (range, 1Ð 4). The overall scores (CFS-APQ1, CFS-APQ2) were obtained by counting all item scores and by dividing this sum by the amount of properly completed questions (possible score range, 1-16). A CFS-APQ1 score of 1 indicates no activity limitations or participation restrictions, whereas 16 represents the maximum score; for CFS-APQ2 the scores range between 1 and 4. When using the Dutch version of the CFS-APQ in a sample of 47 adult patients with CFS, the Cronbach alpha coefficient was .94 and the test-retest reliability coefficients of the overall scores were .95 or greater (P<.001) (time interval, 24h). 12 In the same study, the overall scores on the CFS-APQ correlated significantly with visual analog scales (VASs) for pain (rho=.51, P<.001) and fatigue (rho=.50, P<.001), substantiating the convergent validity of the scores obtained with the Dutch CFS-APQ (both the VASs and CFS-APQ are believed to measure a different indicator of the concept of CFS health status). 12 Additionally, data documenting the content validity of this measure in CFS patients have been reported. 12 (An English and a French version of the CFS-APQ are available on request from the corresponding author.) The Dutch TSK-CFS aims at monitoring kinesiophobia in patients with CFS. The construction, scoring system, and some of its psychometric properties are described in study 1. Exercise testing. Patients performed a bicycle ergometric test against a graded increase in workload until exhaustion was reached. 13 The exercise tests were performed at a humidity of 40% to 60% and at a room temperature of 20 to 22 C. Subjects were asked to take a sitting position on the electromagnetically braked ergometer,^b and after 3 to 5 minutes of adjustment (aiming at physiologic adjustment to exercise by the patients) the test was started. Heart rate was monitored continuously at rest (before the adjustment period) and during exercise. There was continuous recording of the 12-lead electrocardiogram by using an electrocardiograph.^c To collect pulmonary data during the test, an open-circuit spirometer^d with automatic printout every 30 seconds was used. Automatically, averages were attained for peak oxygen consumption (VO_2 peak) and maximal carbon dioxide production during every 30-second interval for the duration of each stage of the exercise. A 2-way breathing valve attached to a mask, which covered the patients' nose and mouth, was used to collect the expired air. The air was analyzed continuously for ventilatory and metabolic variables. Before each test, the spirometer was calibrated for environmental conditions (ie, the environmental conditions 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 suggested as being an optimal test period. 36 To avoid early onset of fatigue in the lower extremities because of inadequate physical fitness, the duration of the exercise was kept below 15 minutes. All subjects started the test at 10W/min, with an increase of 10W/min. 13 The following parameters were obtained: heart rate at rest (HRrest), peak heart rate (HRpeak), exercise duration, maximal work capacity attained, VO peak, VO_2 peak per kilogram of body weight, functional aerobic impairment, peak respiratory quotient (RQpeak), and the percentage of target heart rate achieved (% THR). The age-predicted HRpeak was calculated as 220 minus the subject's age in years. 37 The metabolic data analyzed were the means of the last 30 seconds from the final stage (ie, the values measured over the last 30 seconds for each subject were averaged to obtain a 30-second mean) of exercise or the highest value attained if a decline in VO_2 occurred at the final workload. 13 Functional aerobic impairment is the percentage difference between observed VO_2 peak and the VO_2 peak predicted for a healthy person of the same age, gender, and habitual activity status. 38 VO 2 peak for any age can be predicted by using the regression equations from reference 38; for the purpose of our study, we used the equations for sedentary individuals. Exercise capacity testing is widely used for the disability assessment of patients with CFS, and it appears to be both reproducible and valid. 39,40 The bicycle stress testing protocol used in our study was able to distinguish between female CFS patients and healthy sedentary females. 13 Statistical analysis. All data were entered into Microsoft Excel 2000^e and then analyzed by using SPSS, version 10.0,^a for Windows. Appropriate descriptive statistics (mean, SD, frequencies, percentages, median, IQR) were used. Again, the Cronbach alpha coefficient was calculated as a measure for estimating the internal consistency of the item scores of the questionnaire. Correlations between the scores obtained with the Dutch TSK-CFS and the disability parameters (CFS-APQ, exercise capacity) were assessed by using the Spearman rank correlation coefficient. Because it is well established that women have a lower maximal oxygen uptake than men, pooling of gender data may bias the results. 16 The dataset was therefore reanalyzed by excluding all men. The significance level was set at .01, to help protect against potential type I errors. Finally, patients were divided into 2 groups, based on their ability to perform a maximal effort during the exercise testing (defined by 2 endpoints: RQpeak>=1.0 and an age-predicted target heart rate of at least 85% 13). This was done to examine whether patients with CFS capable of performing a maximal effort have less kinesiophobia than those incapable of attaining the requirements for a maximal effort. The differences between these 2 groups were assessed by using the Levene test for equality of variances, Student t test (independent samples t test, 2-tailed for illness duration and age), Fisher exact test (gender), and independent samples nonparametric Mann-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 was used to examine whether the age and illness duration of both groups were normally distributed. The level of significance was set at .05. RESULTS Study 1 The Dutch TSK-CFS scores ranged between 24 and 54; the median was 40 and the IQR was 11.8. Twenty-five of the 40 patients (62.5%) attained a Dutch TSK-CFS total score greater than 37, indicating high fear of movement. 21,25 For the avoidance/abide subscale of the UCL, the median score and IQR were 9 and 3, respectively, (range, 4-13). The total scores on the Baecke Questionnaire ranged between 4 and 9 (median=7.13, IQR=1.37). The Cronbach alpha coefficient for the individual item scores on the TSK-CFS was .80. The total scores on the Dutch TSK-CFS showed a statistically significant correlation with the UCL avoidance/abide subscale (rho=.35, P=.029) and the Baecke Questionnaire total score (rho=.45, P=.004). Study 2 The Dutch TSK-CFS scores ranged between 30 and 55; the median score was 42 and the IQR was 10.0. Thirty-five of the 51 patients (68.6%) attained a Dutch TSK-CFS total score greater than 37, indicating high fear of movement. 21,25 According to the exercise capacity data, the minority of the subjects (n=16; 31.4%) had no functional impairment (functional aerobic impairment 27% 38). Eight patients with CFS (15.7%) showed evidence of mild functional aerobic impairment (functional aerobic impairment, 27%-40%), whereas the remaining 27 (52.9%) had moderate to marked functional aerobic impairment. By using the American Medical Association Guidelines for Impairment Rating, 41 4 patients (7.8%) were classified as having "no impairment of the whole person" (VO_2 peak/body weight, >25mL/kg/min), and 11 (21.6%) had "mild impairment of the whole person." The majority of the sample (n=36; 70.6%) corresponded to class 3 or 4, suggestive of "moderate to severe impairment of the whole person" (VO_2 peak/body weight, <15mL/kg/min). All descriptive data of the disability assessment are in table 1. The Cronbach alpha for the individual item scores on the TSK-CFS was .74. The Dutch TSK-CFS total scores showed a statistically significant correlation to both total scores on the CFS-APQ (rho=.39, P=.004 for CFS-APQ1; rho=.44, P=.001 for CFS-APQ2). No statistically significant associations were observed between the exercise capacity parameters and the total scores of the Dutch TSK-CFS (table 2). Analyzing only the data from the women (n=45) did not change the outcome: again no statistically significant associations were observed for any of the exercise capacity parameters (data not shown). When patients who did not perform a maximal exercise capacity test (n=24; Dutch TSK-CFS median=41.0; IQR=10.0) were compared with the maximal group (n=27; median43.0; IQR=10.0), no statistically significant differences in the total scores obtained with the Dutch TSK-CFS were observed (Mann-Whitney U=302.0, z=.166, P=.868). Comparing the demographic 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 alpha coefficient was .80, indicating sufficient internal consistency of the item scores of the Dutch TSK-CFS. 42 The Cronbach alpha was slightly lower in study 2 (.74). Because the Dutch TSK-CFS total scores showed a statistically significant correlation with the UCL avoidance/abide subscale scores, evidence for the congruent validity of the Dutch TSK-CFS total scores was provided. The convergent validity of the scores obtained with the Dutch TSK-CFS (assessing avoidance of activity as an indicator of CFS-associated inactivity) was supported by the observed statistically significant inverse correlation with the overall scores of the Baecke Questionnaire (assessing habitual physical activity as a second indicator 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 TSK-CFS remain to be established. No data are currently available to validate the English version of the TSK-CFS (appendix 1). Study 2 At least a subset of patients with CFS can be characterized by avoidance of physical activity as a coping strategy. 43 By using the cutoff point of 37, 21,25 the prevalence of kinesiophobia among the patients with CSF examined in studies 1 and 2 was 60 out of 91 (65%). These data provide evidence for a high prevalence of kinesiophobia among adult patients with CSF who seek treatment for their complaints. Because our sample was not randomly selected from the CFS community, we are unable to extrapolate these results to the entire CFS population. This prevalence rate was considerably higher than that reported by Silver et al 21 (15/33, 45.5%). However, this might be explained by the high number of tertiary referrals seen in our specialized chronic fatigue clinic. Numerous investigators and clinicians have speculated that avoidance behavior toward physical activity may actually be maladaptive and cause a greater burden in patients with CFS. 4-6 This view is partly supported by the present report; a strong association between kinesiophobia and self-reported activity limitations and participation restrictions was observed (rho=.39, P.=004 for CFS-APQ1; rho=.44, P=.001 for CFS-APQ2). Because the CFS-APQ also queries social interactions, these results are in accordance with the Heijmans study, 5 which found cognitive-avoidant coping to be negatively related to social functioning (R=.26, P=.01). To our knowledge, ours is the first report addressing the association among fear of movement (kinesiophobia), a specific kind of fear-avoidance behavior, and disability in patients with CFS. Still, long-term followup studies are required to establish a causal relationship between kinesiophobia and daily functioning. The exercise capacity data confirmed earlier reports that provide evidence for a reduced exercise capacity in patients with CSF. 13-15 We hypothesized that avoidance behavior toward physical activity might prevent patients with CSF from performing 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 of target heart rate achieved and the duration of the stress test) were inversely correlated with kinesiophobia, at least not in this consecutively allocated sample of patients with CSF. In addition, when comparing patients who did not perform a maximal exercise capacity test with the maximal group, no statistically significant differences in the total scores obtained with the Dutch TSK-CFS were found. Thus, it appears that exercise capacity and kinesiophobia are unrelated in adult patients with CFS who seek treatment for their symptoms. These results are in accordance with the Silver study, 21 which found no association between kinesiophobia and the maximal heart rate or the resting heart rate in patients with CFS. Silver did not collect metabolic or ventilatory parameters. When interpreting these results as they apply to the practice of physical therapy and rehabilitation medicine, we suggest using the Dutch TSK-CFS for the assessment of kinesiophobia in patients with CFS. Furthermore, because evidence substantiating the clinical importance of kinesiophobia in patients with CSF was provided (ie, the associations between the kinesiophobia and activity limitations and participation restrictions), kinesiophobia should become the focus of management strategies at least in those patients with CSF presenting with high fear of movement. Graded exercise therapy and cognitive behavioral therapy have been suggested as strategies to reduce avoidance behavior toward physical activity in CFS patients. 7 However, a recent study 44 explored whether exercise induces a significantly greater complement activation (an important component of the immune system) in persons with CFS than in healthy controls. Among the patients with CSF studied, the complement activation was significantly associated with a postexercise increase in symptom severity. 44 This, together with the results of a treatment audit among British CFS patients, showing that 50% of all patients who had tried graded exercise reported that this had worsened their condition, 45 might motivate CFS practitioners and researchers to search for other therapies capable of reducing kinesiophobia in CFS patients. To reduce kinesiophobia without using graded exercise therapy, 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 Vlaeyen et al, 46 but its effectiveness in patients with CSF has yet to be established. 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. To help protect against potential type I errors, the significance level was set at .01. Second, the study design did not allow us to draw conclusions about causality. Third, no data documenting the test-retest reliability of the Dutch TSK-CFS are currently available. CONCLUSIONS The results of study 1 substantiate the internal consistency and the congruent and the convergent validity of the scores obtained with the Dutch TSK-CFS. The data presented in study 2 suggest that kinesiophobia and activity limitations and participation restrictions are related in adult patients with CFS who seek treatment for their symptoms. There appears to be no association between exercise capacity and kinesiophobia in adult patients with CFS who seek treatment for their symptoms. More work is needed to examine the causal relationship between kinesiophobia and activity limitations and participation restrictions, as well as to explain the reduced exercise capacity in patients with CFS. Acknowledgments: We thank Lieve De Hauwere (GFN) for her help during the exercise capacity stress testing, and Katrien Vanher-berghen, PT, for editing the final version of the manuscript. We are grateful to Elke Van Hoof, PhD, for assisting in the scoring of the UCL and for critical review of the study proposal. APPENDIX 1: THE ITEMS OF THE TSK-CFS/VERSION 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 would increase. 3. My body is telling me I have something dangerously wrong. 4. My symptoms would probably be relieved if I were to exercise. 5. People are not taking my medical condition seriously enough. 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 not mean it is dangerous. 9. I am afraid that I might injure myself accidentally. 10. Simply being careful that I do not make any unnecessary movements is the safest thing I can do to prevent my symptoms from worsening. 11. I would not have this many symptoms if there was not something potentially dangerous going on in my body. 12. Although I have many symptoms, I would be better off if I were physically active. 13. My symptoms let me know when to stop exercising so that I do not harm myself. 14. It is really not safe for a person with a condition like mine to be physically active. 15. I cannot do all the things normal people do because it is too easy for me to get injured. 16. Even though something is aggravating my symptoms, I do not think it is actually dangerous. 17. I should not have to exercise when I am experiencing symptoms. TABLES Table 1: Descriptive Data of the Dutch TSK-CFS and the Disability Assessment (n=51) ---------------------------------------------------------------------------- Questionnaires Median IQR Range ---------------------------------------------------------------------------- Dutch TSK-CFS* 42.0 10.0 30.0-55.0 CFS-APQ1** 8.6 3.7 4.4-15.1 CFS-APQ2*** 2.8 1.0 1.5- 3.8 ---------------------------------------------------------------------------- Exercise Capacity Parameter Mean p/m SD Range ---------------------------------------------------------------------------- Exercise duration (min) 9.7 p/m 3.0 4.4-18.2 HRrest (bpm) 86.6 p/m 15.4 54.0-133.0 HRpeak (bpm) 149.3 p/m 22.4 102.0-197.0 Workload (W) 94.0 p/m 30.4 40.0-160.0 Workload per body weight (w/kg) 1.4 p/m 0.4 0.6-2.9 VO_2 peak (L/min) 1196.8 p/m 368.7 600.0-2099.0 VO_2 peak/body weight (mL/kg/min) 17.1 p/m 5.9 6.6-31.8 % functional aerobic impairment 39.9 p/m 21.2 7.9-77.4 RQpeak 1.1 p/m 0.1 0.9-1.4 %THR 83.5 p/m 12.2 58.0-112.0 ---------------------------------------------------------------------------- * 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 participation restrictions; 16 represents the maximum score. ***The CFS-APQ2 scores range between 1 and 4. Table 2: Correlation Analysis Between the Dutch TSK-CFS Scores and the Disability Parameters (n=51) ---------------------------------------------------------------------------- rho Dutch TSK-CFS* P Value** ---------------------------------------------------------------------------- CFS-APQ1*** .39 .00* CFS-APQ2**** .44 .00* Illness duration .02 .92 Exercise duration (min) .09 .55 HRpeak (bpm) .15 .29 Workload (W) .10 .51 Workload per body weight (w/kg) .09 .53 VO_2 peak (L/min) .07 .62 VO_2 peak/body weight (mLkg 1 min 1) .10 .50 % functional aerobic impairment .04 .76 RQpeak .03 .85 %THR .14 .33 ---------------------------------------------------------------------------- * Total scores on the Dutch TSK-CFS range between 17 and 68; higher scores indicate a higher degree of kinesiophobia. ** Significant at .01. *** A CFS-APQ1 score of 1 indicates no activity limitations or participation restrictions; 16 represents the maximum score. ****The CFS-APQ2 scores range between 1 and 4. References 1. Fukuda K, Straus SE, Hickie I, Sharpe MC, Dobbins JG, Komaroff A. The chronic fatigue syndrome: a comprehensive approach to its definition and study. International Chronic Fatigue Syndrome Study Group. Ann Intern Med 1994; 121: 953-9. 2. Clapp LL, Richardson MT, Smith JF, Wang M, Clapp AJ, Pieroni RE. Acute effects of thirty minutes of light-intensity, intermittent exercise on patients with chronic fatigue syndrome. Phys Ther 1999; 78: 749-56. Comment in: Phys Ther 2000; 80: 115. 3. Fischler B, Dendale P, Michiels V, Cluydts R, Kaufman L, De Meirleir K. Physical fatigability and exercise capacity in chronic fatigue syndrome: association with disability, somatization and psychopathology. J Psychosom Res 1997; 42: 369-78. 4. Van Houdenhove B. Chronische pijn, chronische vermoeidheid: een indicatie voor "psychosomatische revalidatie". Tijdschr Geneeskd 1996; 52: 1371-8. 5. Heijmans MJ. Coping and adaptive outcome in chronic fatigue syndrome: importance of illness cognitions. J Psychosom Res 1998; 45: 39-51. 6. Ray C, Jefferies S, Weir WR. Coping and other predictors of outcome in chronic fatigue syndrome: a 1-year followup. J Psychosom Res 1997; 43: 405-15. 7. Powell P, Bentall RP, Nye FJ, Edwards RH. Randomised controlled trial of patient education to encourage graded exercise in chronic 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 with chronic fatigue syndrome. Cochrane Database Syst Rev 2000;(2): CD001027. 10. Franklin B, Whaley MH, Howley ET. ACSM's guidelines for exercise testing and prescription. 6th ed. Philadelphia: Lippincott Williams & Wilkins; 2000. p 117. 11. Nijs J, Vaes P, Van Hoof E, De Becker P, McGregor N, De Meirleir K. Activity limitations and participation restrictions in patients with chronic fatigue syndrome - construction of a disease specific questionnaire. J Chronic Fatigue Syndr 2002; 10: 3-23. 12. Nijs J, Vaes P, McGregor N, Van Hoof E, De Meirleir K. Psychometric properties of the Dutch Chronic Fatigue Syndrome - Activities and Participation Questionnaire (CFS-APQ). Phys Ther 2003; 83: 444-54. 13. De Becker P, Roeykens J, Reynders M, McGregor N, De Meirleir K. Exercise capacity in chronic fatigue syndrome. Arch Intern Med 2000; 160: 3270-7. 14. Riley MS, O'Brien 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 cardio-vascular effects of a progressive exercise test in patients with chronic 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 in chronic 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 of chronic pain behavior. Pain Manage 1990; Jan/Feb: 35-43. 19. Goubert L, Crombez G, Vlaeyen J, Van Damme S, Van den Broeck A, Van Houdenhove B. De Tampa schaal voor Kinesiofobie: psychometrische karakteristieken en normering. Gedrag Gezondheid 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. J Occup Rehabil 1995; 5: 235-52. 21. Silver A, Haeney M, Vijayadurai P, Wilks D, Pattrick M, Main CJ. The role of fear of physical movement and activity in chronic fatigue syndrome. J Psychosom Res 2002; 52: 485-93. 22. Waddell G, Newton M, Henderson I, Somerville D, Main CJ. A fear-avoidance beliefs questionnaire (FABQ) and the role of fear-avoidance beliefs in chronic low back pain and disability. Pain 1993; 52: 157-68. 23. A report of the CFS/ME Working Group. Report to the Chief Medical Officer of an independent working group. London: Department of Health; 2001. Available at: http://www.doh.gov.uk/cmo/cfsmereport/index.htm. Accessed December 21, 2003. 24. Holmes GP, Kaplan JE, Gantz NM, et al. Chronic fatigue syndrome: a working case definition. Ann Intern Med 1988; 108: 387-9. 25. Vlaeyen JW, Kole-Snijders AM, Boeren RG, van Eek H. Fear of movement/ (re)injury in chronic low back pain and its relation to behavioral performance. Pain 1995; 62: 363-72. 26. Schreurs PJ, Tellegen B, Van de Willige G. Gezondheid, stress en coping: de ontwikkeling van de Utrechtse Coping Lijst. Tijdschr Psychol 1984; 12: 101-17. 27. Schreurs PJ, Van de Willige G, Brosschot JF, Tellegen B, Graus GM. De Utrechtse Coping Lijst UCL. Omgaan met problemen en gebeurtenissen. Herziene handleiding. Lisse: Swets Test Services; 1993. 28. Sanderman R, Ormel J. De Utrechtse Coping Lijst (UCL): validiteit en betrouwbaarheid. Gedrag Gezondheid 1992; 20: 32-7. 29. Oldehinkel AJ, Koeter MW, Ormel J, Van den Brink W. Omgaan met problema- tische situaties: de relatie tussen algmeneen en situatiespecifiek copinggedrag. Gedrag Gezondheid 1992; 20: 236-45. 30. Schaufeli W, van Dierendonck D. De betrouwbaarheid en validiteit van de Utrechtse Coping Lijst. Een longitudinaal onderzoek bij schoolverlaters. Gedrag Gezondheid 1992; 20: 38-45. 31. Baecke JA, Burema J, Frijters JE. A short questionnaire for the measurement of habitual physical activity in epidemiological studies. Am J Clin Nutr 1982; 36: 936-42. 32. Pols MA, Peeters PH, Bueno-De-Mesquita HB, et al. Validity and repeatability of a modified Baecke questionnaire on physical activity. Int J Epidemiol 1995; 24: 381-8. 33. Richardson MT, Ainsworth BE, Wu HC, Jacobs DR, Leon AS. Ability of the atherosclerosis risk in communities (ARIC)/Baecke Questionnaire to assess leisure-time physical activity. Int J Epidemiol 1995; 24: 685-93. 34. Jacobs DR Jr, Ainsworth BE, Hartman TJ, Leon AS. A simultaneous evaluation of ten commonly used physical activity questionnaires. Med Sci Sports Exerc 1993; 25: 81-91. 35. Anderson JS, Ferrans CE. The quality of life of persons with chronic fatigue syndrome. J Nerv Ment Dis 1997; 185: 359-67. 36. Davis JA. Direct determination of aerobic power. In: Maud PJ, Foster C, editors. Physiological assessment of human fitness. Champaign: Human Kinetics; 1995. p 9-17. 37. Astrand PO, Rodahl K. Evaluation of physical performance in the basis of tests. In: Astrand PO, Rodahl K, editors. Textbook of work physiology: physiological bases of exercise. 3rd ed. New York: McGraw-Hill; 1986. p 354-87. 38. Bruce RA, Kusumi F, Hosmer D. Maximal oxygen intake and normographic assessment of functional aerobic impairment in cardiovascular disease. Am Heart J 1973; 85: 546-62. 39. Manu P, Affleck G, Tennen H, Morse PA, Escobar JI. Hypochondriasis influence quality-of-life outcomes in patients with chronic fatigue. Psychother Psychosom 1996; 65: 76-81. 40. Peterson DL. Chronic Fatigue Syndrome and disability: editorials. J Chronic Fatigue Syndr 1997; 3: 5-7. 41. Make B, Jones JF. Impairment of patients with Chronic Fatigue Syndrome. J Chronic Fatigue Syndr 1997; 3: 43-55. 42. Dijkers MP, Kropp GC, Esper RM, Yavuzer G, Cullen N, Bakdalieh Y. Reporting on reliability and validity of outcome measures in 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 and chronic fatigue syndrome. J Psychosom Res 2000; 48: 547-54. 44. Sorensen B, Streib JE, Strand M, et al. Complement activation in a model of chronic fatigue syndrome. J Allergy Clin Immunol 2003; 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 back pain: further evidence on the effectiveness of exposure in vivo. Clin J Pain 2002; 18: 251-61. Suppliers a. SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606. b. Jaeger 900; Lode BV, Zernikepark 16, 9747 AN Groningen, The Netherlands. c. GE Medical Systems, Milwaukee, WI. d. Mijnhart Oxycon; IBM, Bunnik, the Netherlands. e. Microsoft Corp, One Microsoft Wy, Redmond, WA 98052. -------- (c) 2004 W.B. Saunders (c) 2004 American Congress of Rehabilitation Medicine (c) 2004 American Academy of Physical Medicine and Rehabilitation