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PubMed2001

Developing measures of fatigue using an alcohol comparison to validate the effects of fatigue on performance.

The effects of 28 h of sleep deprivation were compared with varying doses of alcohol up to 0.1% blood alcohol concentration (BAC) in the same subjects. The study was conducted in the laboratory. Twenty long-haul truck drivers and 19 people not employed as professional drivers acted as subjects. Tests were selected that were likely to be affected by fatigue, including simple reaction time, unstable tracking, dual task, Mackworth clock vigilance test, symbol digit coding, visual search, sequential spatial memory and logical reasoning. While performance effects were seen due to alcohol for all tests, sleep deprivation affected performance on most tests, but had no effect on performance on the visual search and logical reasoning tests. Some tests showed evidence of a circadian rhythm effect on performance, in particular, simple reaction time, dual task, Mackworth clock vigilance, and symbol digit coding, but only for response speed and not response accuracy. Drivers were slower but more accurate than controls on the symbol digit test, suggesting that they took a more conservative approach to performance of this test. This study demonstrated which tests are most sensitive to sleep deprivation and fatigue. The study therefore has established a set of tests that can be used in evaluations of fatigue and fatigue countermeasures.

Accidents, Traffic↗
PubMed1997

The relation of sleep difficulties to fatigue, mood and disability in chronic fatigue syndrome.

The relationship of sleep complaints to mood, fatigue, disability, and lifestyle was examined in 69 chronic fatigue syndrome (CFS) patients without psychiatric disorder, 58 CFS patients with psychiatric disorder, 38 psychiatric out-patients with chronic depressive disorders, and 45 healthy controls. The groups were matched for age and gender. There were few differences between the prevalence or nature of sleep complaints of CFS patients with or without current DSM-IIIR depression, anxiety or somatization disorder. CFS patients reported significantly more naps and waking by pain, a similar prevalence of difficulties in maintaining sleep, and significantly less difficulty getting off to sleep compared to depressed patients. Sleep continuity complaints preceded fatigue in only 20% of CFS patients, but there was a strong association between relapse and sleep disturbance. Certain types of sleep disorder were associated with increased disability or fatigue in CFS patients. Disrupted sleep appears to complicate the course of CFS. For the most part, sleep complaints are either attributable to the lifestyle of CFS patients or seem inherent to the underlying condition of CFS. They are generally unrelated to depression or anxiety in CFS.

Activities of Daily Living↗
PubMed1995

Coping with chronic fatigue syndrome: illness responses and their relationship with fatigue, functional impairment and emotional status.

The implications of patients' approaches to managing chronic fatigue syndrome were examined in a cross-sectional study. With severity of fatigue controlled, attempting to maintain activity was associated with less functional impairment, while accommodating to the illness was positively related to impairment; behavioural disengagement was related not only to higher levels of impairment but also to greater emotional disturbance. Fatigue itself was positively associated with focusing on symptoms and with behavioural disengagement; it was associated also with illness accommodation, but only for illness of longer duration. The causal direction of relationships between coping and fatigue severity is ambiguous, and a follow-up study will address the effects of coping on changes in the illness over time.

Adaptation, Psychological↗
PubMed2002

Assessment of fatigue in patients with chronic hepatitis C using the Fatigue Impact Scale.

The aim of this study was to assess the impact of fatigue on the quality of life of patients with chronic hepatitis C (CHC) and to examine its relationship with various parameters of the disease, including viral load. The Fatigue Impact Scale (FIS), a self-report questionnaire, was applied to 92 patients with CHC, and the results were compared to those of an age-matched cohort of 213 healthy blood donors. Fatigue was frequent and disabling, being present in 67% of CHC patients, and the FIS was significantly increased in CHC patients compared to the healthy controls. Fatigue severity was not correlated with the activity of the disease or with the level of viremia. The FIS proved to be a valuable tool to assess this symptom. It should be of help for better evaluation of the clinical spectrum of the disease and should be included in trials assessing the efficacy of therapeutic interventions.

Adult↗
PubMed2000

Perceived fatigue after mental work: an experimental evaluation of a fatigue inventory.

The aim of this study was to investigate the perceived fatigue after mental work and to test the Swedish Occupational Fatigue Inventory (SOFI). Twenty male and 20 female participants worked with proof reading (2 x 90 min) and a vigilance task (2 x 60 min). After each task session, perceived fatigue was rated with the SOFI and Borg's CR10O-scale. In addition, physiological reactions were registered; blood pressure, heart rate, heart rate variability and muscle activity in corrugator supercilii, as well as measures of performance: reaction time, number of pages read and number of proof errors found, number of detected signals. As expected, the highest ratings were obtained on Lack of energy, Lack of motivation and Sleepiness, particularly after the vigilance task. High ratings after both work tasks were also found on the CR10-scale. Men and women did not differ significantly with respect to their ratings. No clear-cut physiological reactions were found to correlate with ratings of fatigue. The results indicate the validity of the mental dimension of the SOFI.

Electromyography↗
PubMed2001

Differences in fatigue and psychological distress across occupations: results from the Maastricht Cohort Study of Fatigue at Work.

Differences in fatigue and psychological distress across occupations were examined among 8521 employees participating in the Maastricht Cohort Study of "Fatigue at Work." Additional information on the perceived psychosocial work environment was incorporated. A total of 131 occupations, classified according to the Netherlands Standard Classification of Occupations 1992, were studied. Results showed that occupation as a proxy index of the "objective" work environment adds little explanatory information beyond perceived measures of the work environment. Although "occupation" seems to be an easy entree for intervention, focusing on occupation exclusively to prevent, or at least reduce, fatigue and psychological distress may be inadequate. Supplementary information about the perceived work environment of the job occupant is needed to develop preventive measures on the individual level. Further research, including a longitudinal analysis, is required to elucidate the complex relation between occupation, psychosocial risk factors, and fatigue and psychological distress.

Adult↗
PubMed1993

Central basis of muscle fatigue in chronic fatigue syndrome.

We studied whether muscle fatigue, metabolism, or activation are abnormal in the chronic fatigue syndrome (CFS). Subjects performed both an intermittent submaximal and a sustained maximal voluntary isometric exercise protocol of the tibialis anterior muscle. The extent of fatigue, metabolic response, and changes in both M-wave amplitude and twitch tension during exercise were similar in patients and controls. The response to systemic exercise was also normal in the patients. However, voluntary activation of the tibialis was significantly lower in the patients during maximal sustained exercise. The results indicate that patients with CFS have (1) normal fatigability and metabolism at both the intracellular and systemic levels, (2) normal muscle membrane function and excitation-contraction coupling, and (3) an inability to fully activate skeletal muscle during intense, sustained exercise. This failure of activation was well in excess of that found in controls, suggesting an important central component of muscle fatigue in CFS.

Adult↗
PubMed2003

Perceived exertion in fatiguing illness: Gulf War veterans with chronic fatigue syndrome.

PURPOSE: It has been reported that ratings of perceived exertion (RPE) are elevated in chronic fatigue syndrome (CFS). We have challenged this notion by examining perceived exertion in civilian females with CFS and expressing the data relative to exercise capacity (%[OV0312]O(2max)). The purpose of the present investigation was to further examine RPE during exercise in a unique population of CFS patients, Gulf veterans (GV). METHODS: Thirty-four GV (N = 15 CFS, 42 +/- 8 yr; N = 19 healthy, 43 +/- 5 yr) performed a maximal exercise test on a cycle ergometer. After a 3-min warm-up, exercise intensity increased by 30 W every minute until exhaustion. RPE were obtained during the last 15 s of each minute using Borg's CR-10 scale. RESULTS: With the exception of peak [OV0312]E, there were no significant differences in any peak exercise variables. Repeated measures ANOVA revealed significantly higher RPE at each power output examined (F(1,32) = 16.4, P < 0.001). Group differences in RPE remained significant when analyzed relative to peak [OV0312]O(2) (F(1,32) = 7.2, P = 0.01). Both group main effects and the interaction were eliminated when self-reported fatigue symptoms were controlled for in the analyses. Power functions for RPE as a function of relative oxygen consumption were not different between groups and were significantly greater than a linear value of 1.0 (1.6 +/- 0.3 for both groups, P < 0.02). CONCLUSIONS: Our results show that RPE are greater in GV with CFS regardless of whether the data were expressed in terms of absolute or relative exercise intensity. However, self-reported fatigue associated with CFS eliminated the group differences. These results suggest that GV with CFS were unique compared with their civilian counterparts. Future research aimed at determining the influence of preexisting fatigue on RPE during exercise is warranted.

Adult↗
PubMed1998

Concurrent validity of the Beck Depression Inventory and the multidimensional fatigue inventory-20 in assessing fatigue among cancer patients.

Cancer patients experience both fatigue and depression while undergoing treatment for their disease. A number of authors have conceptualized such depression among this populations as secondary to fatigue. This study of 54 patients was done to test the concurrent validity of two inventories. Scores on the five subscales of the 20-item Multidimensional Fatigue Inventory were correlated with those on the 21-item Beck Depression Inventory. Moderate correlations are reported and the potential usefulness of the Multidimensional Fatigue Inventory is discussed.

Adaptation, Psychological↗
PubMed2001

Is physical deconditioning a perpetuating factor in chronic fatigue syndrome? A controlled study on maximal exercise performance and relations with fatigue, impairment and physical activity.

BACKGROUND: Chronic fatigue syndrome (CFS) patients often complain that physical exertion produces an increase of complaints, leading to a greater need for rest and more time spent in bed. It has been suggested that this is due to a bad physical fitness and that physical deconditioning is a perpetuating factor in CFS. Until now, studies on physical deconditioning in CFS have shown inconsistent results. METHODS: Twenty CFS patients and 20 matched neighbourhood controls performed a maximal exercise test with incremental load. Heart rate, blood pressure, respiratory tidal volume, O2 saturation, O2 consumption, CO2 production, and blood-gas values of arterialized capillary blood were measured. Physical fitness was quantified as the difference between the actual and predicted ratios of maximal workload versus increase of heart rate. Fatigue, impairment and physical activity were assessed to study its relationship with physical fitness. RESULTS: There were no statistically significant differences in physical fitness between CFS patients and their controls. Nine CFS patients had a better fitness than their control. A negative relationship between physical fitness and fatigue was found in both groups. For CFS patients a negative correlation between fitness and impairment and a positive correlation between fitness and physical activity was found as well. Finally, it was found that more CFS patients than controls did not achieve a physiological limitation at maximal exercise. CONCLUSIONS: Physical deconditioning does not seem a perpetuating factor in CFS.

Activities of Daily Living↗
PubMedDate not supplied

Physiologic measurement of exercise and fatigue with special reference to chronic fatigue syndrome.

Oxidative metabolism is the major source of energy for muscle activity, and maximal oxygen uptake (VO2max), the product of maximal cardiac output and maximal arteriovenous oxygen difference, indicates individual capacity for oxidative metabolism and performance of exercise by the large muscles. Strength, a function of muscle cross-sectional area, motor-unit recruitment, and neuromuscular coordination, is the ability to develop force in a single, brief, maximal-effort voluntary contraction of rested muscle. Weakness is a diminished ability of rested muscle to exert maximal force. Fatigue is a loss of maximal force-generating capacity that develops during muscular activity, likely originates within muscle itself, and persists until muscle is fully recovered. Individual perception of motor effort can be determined with standardized rating scales. These concepts are discussed in detail, their relevance to the pathophysiology of exercise in chronic fatigue syndrome is analyzed, and a general strategy of exercise evaluation pertinent to chronic fatigue syndrome is presented.

Exercise↗
PubMed1997

Markers of inflammation and immune activation in chronic fatigue and chronic fatigue syndrome.

OBJECTIVE: Chronic fatigue syndrome (CFS) has been hypothesized to result from immune activation. We examined the role of serum markers of inflammation and immune activation among patients with CFS and in those with chronic fatigue (CF) not meeting the case definition. METHODS: Assays for soluble interleukin 2 (IL-2) receptor, IL-6, C-reactive protein, beta 2-microglobulin, and neopterin were performed in 153 fatigued patients in a referral clinic. Patients were classified according to whether they met criteria for CFS, reported onset of illness with a viral syndrome or had a temperature > 37.5 degrees C on examination. RESULTS: Compared to control subjects, mean concentrations of C-reactive protein, beta 2-microglobulin, and neopterin were higher in patients with CFS (p < or = 0.01) and CF (p < or = 0.01). Results did not distinguish CFS from CF. IL-6 was elevated among febrile patients compared to those without this finding (p < or = 0.001), but other consistent differences between patient subgroups were not observed. The presence of several markers was highly correlated (p < 0.01). CONCLUSION: Our findings that levels of several markers were significantly correlated points to a subset of patients with immune system activation. Whether this phenomenon reflects an intercurrent, transient, common condition, such as an upper respiratory infection, or is the result of an ongoing illness associated process is unknown. Overall, serum markers of inflammation and immune activation are of limited diagnostic usefulness in the evaluation of patients with CSF and CF.

Adult↗
PubMed2000

Potentiating and fatiguing cortical reactions in a voluntary fatigue test of a human hand muscle.

Fatigue-associated changes in the excitability of central motor mechanisms were investigated using transcranial magnetic stimulation (TMS) of the motor cortex. Test stimuli were applied before, during and after a voluntary fatigue test of the first dorsal interosseus muscle (FDI). Subjects were required to maintain 50% of their maximum voluntary force (MVC) for at least 2 min (1/2-MVC test) and electromyographic (EMG) reactions of FDI were measured with surface electrodes. Prior to the test, TMS pulses of 70% maximum output (about 1.4 T) produced muscle-evoked potentials (MEPs) of widely different amplitudes in different subjects, ranging from 13% to 55% of the maximum compound action potential (M-wave) evoked by ulnar nerve stimulation. During the test, MEPs of all subjects showed a potentiation; this effect was markedly greater in subjects with a small initial MEP. After the test, the differential degrees of contraction-evoked potentiation still influenced the MEP amplitudes; small pre-test MEPs showed a post-test net potentiation and larger pre-test MEPs showed a net post-test depression. The results underline that the net outcome of motor activation on motor cortex excitability, as studied with TMS, depends on a complex balance of fatiguing and potentiating effects.

Action Potentials↗
PubMed1997

Screening for psychiatric disorders in chronic fatigue and chronic fatigue syndrome.

Psychiatric disorders are common in chronic fatigue (CF) and chronic fatigue syndrome (CFS). To determine the usefulness of the General Health Questionnaire (GHQ), a self-report measure of psychological distress, in identifying those with psychiatric illnesses, a structured psychiatric interview and the GHQ were administered to 120 CF and 161 CFS patients seen in a referral clinic. Overall, 87 (35%) patients had a current and 210 (82%) a lifetime psychiatric disorder. Compared to patients without psychiatric disorders, GHQ scores above the threshold (> or = 12) were more frequent among patients with current (p < 0.001) and lifetime (p < 0.05) diagnoses; scores among patients with CF and CFS were similar. Longer illness duration, greater fatigue severity, and current psychiatric disorders were significant predictors of the GHQ score. In CF and CFS, the best sensitivity (0.69-0.76) and specificity (0.51-0.62) were achieved for current psychiatric diagnoses using a threshold score of > or = 12. Thus, patients scoring < 12 on the GHQ are significantly less likely to have a psychiatric disorder.

Adult↗
PubMed1997

Differential responses in intramuscular pressure and EMG fatigue indicators during low- vs. high-level isometric contractions to fatigue.

This study investigated changes in intramuscular pressure (IMP) and surface electromyographic (EMG) parameters (mean frequency of the power spectrum, f(mean); and signal amplitude denoted as root mean square, RMS) during contractions to fatigue at 25 and 70% of maximal voluntary contraction (MVC). Parameters were recorded simultaneously from the vastus lateralis muscle during knee extension. A significant decrease in f(mean) occurred with time at both contraction levels; however, the rate of decline (slope) was greater at 70% MVC. RMS increased throughout the contractions at both levels, with the relative increase being significantly greater for 25% MVC. IMP increased during 25% MVC but did not change during the 70% MVC contraction. IMP at rest was significantly higher post-contractions than it was pre-contractions at 25% MVC (21.1 vs. 8.0 mmHg, P < 0.01) and 70% MVC (13.7 vs. 8.6 mmHg, P < 0.01). Consequently, post-contraction IMP was higher at 25% MVC than at 70% MVC (P < 0.01). IMP changes throughout the fatiguing contractions correlated negatively with f(mean) and positively with RMS at both MVC levels; however, these correlations were better at 25% MVC. The extent of intramuscular water accumulation is discussed as a major cause of the difference in IMP changes between 25% and 70% MVC. Significant differences in the rate of change for all parameters between high vs. low contraction levels may suggest a common mechanism governing changes in IMP and EMG fatigue indicators.

Adult↗
PubMed2004

Fatigue and recovery after high-intensity exercise part I: neuromuscular fatigue.

The contribution of central and peripheral factors to muscle fatigue were quantified following a high-intensity uphill running exercise. Eight male volunteers performed an intermittent exercise at 120 % of maximal aerobic speed on a treadmill with an 18 % grade. Electrically evoked and voluntary contractions of the knee extensors and EMG of the two vastii were analyzed before and immediately after the high-intensity exercise. Isometric maximal voluntary contraction decreased slightly (-7+/-8 %; p < 0.05) after exercise but no changes were found in the level of maximal activation or in the torque produced by a 80 Hz maximal stimulation applied to the femoral nerve. Following exercise, the single twitch was characterized by lower peak torque, maximal rate of force development, and relaxation (-28+/-11%, -25+/-12%, -31+/-15% respectively, p < 0.001), and higher surface of the M-wave for both vastii. The ratio between the torques evoked by 20 Hz and 80 Hz stimulation declined significantly (-22+/-10%, p < 0.01) after exercise. These findings indicate that muscle fatigue after high-intensity running exercise is due to significant alteration in excitation-contraction coupling and that this type of exercise does not induce significant central fatigue or changes at the crossbridge level.

Adult↗
PubMedDate not supplied

Assessment of fatigue in primary Sjögren's syndrome: the Swedish version of the Profile of Fatigue.

OBJECTIVE: To translate the disease-specific Profile of Fatigue (ProF) into Swedish and to evaluate the reliability and validity of the Swedish version. METHODS: Forward and back translations were performed. Seventy patients with primary Sjögren's syndrome (PSS), 48 control persons, and two rheumatologists participated. Test-retest reliability, internal consistency, content, construct and discriminant validity were investigated. RESULTS: The translation was accepted without modifications. The test-retest reliability varied between moderate and good (weighted Kappa = 0.51-0.63). Internal consistency was high (Cronbach's alpha = 0.97). Construct validity was proved by significant correlations of the questionnaire items with the Visual Analogue Scale (VAS) for fatigue (r(s) = 0.55-0.70), and the Physical Function (PF) (r(s) = -0.20 to -0.41) and Vitality (VT) scales (r(s) = -0.60 to -0.77) of the MOS 36-Item Short-Form Health Survey (SF-36). Content validity was mainly judged as good. A significant difference between the scorings of the patients and the scorings of the control group was seen (mean difference 1.6, p<0.005). CONCLUSION: The Swedish version of the ProF is a relatively reliable and valid instrument for the measurement of fatigue in patients with PSS.

Adult↗
PubMed2003

Validation evidence for the French Canadian adaptation of the Multidimensional Fatigue Inventory as a measure of cancer-related fatigue.

Cancer-related fatigue is the most reported symptom among patients with cancer. Researchers in the field of psychooncology have encouraged the development of short instruments, which allow for easier completion by clinical populations while still maintaining solid psychometric properties. The current study examined the validity and reliability of the French Canadian adaptation of the Multidimensional Fatigue Inventory (MFI) among women (n = 277) and men (n = 327) undergoing therapy for breast or prostate cancer, respectively. An exploratory factor analysis of the selected 15-item MFI yielded the following four factors: general/physical, mental, reduced motivation, and reduced activity. This was supported by a confirmatory factor analysis. The reliability, as evaluated by test-retest and Cronbach alpha internal consistency reliability coefficients of the French Canadian shortened MFI, was acceptable. In addition, the four factor-based scores correlated in a theoretically meaningful manner with existing measures of mood disturbance (Profile of Mood States and Hospital Anxiety and Depression Scale), cancer-related stressors (Inventory of Recent Life Experiences), coping with illness (Coping with Health Injuries and Problems Scale), quality of life (European Organization for Research and Treatment of Cancer Quality of Life Questionnaire), and insomnia (Insomnia Severity Index), suggesting good construct, convergent, and concurrent criterion validity. Although further validation is recommended, the results for the French Canadian MFI in assessing cancer-related fatigue in both women and men undergoing cancer treatments showed good psychometric qualities.

Adaptation, Psychological↗