Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FATIGUE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMed1996

Effects of DAP on diaphragm force and fatigue, including fatigue due to neurotransmission failure.

Among the aminopyridines, 3,4-diaminopyridine (DAP) is a more effective K+ channel blocker than is 4-aminopyridine (4-AP), and, furthermore, DAP enhances neuromuscular transmission. Because 4-AP improves muscle contractility, we hypothesized that DAP would also increase force and, in addition, ameliorate fatigue and improve the neurotransmission failure component of fatigue. Rat diaphragm strips were studied in vitro (37 degrees C). In field-stimulated muscle, 0.3 mM DAP significantly increased diaphragm twitch force, prolonged contraction time, and shifted the force-frequency relationship to the left without-altering peak tetanic force, resulting in increased force at stimulation frequencies < or = 50 Hz. During 20-Hz intermittent stimulation, DAP increased diaphragm peak force compared with control during a 150-s fatigue run and, furthermore, significantly improved maintenance of intratrain force. The relative contribution of neurotransmission failure to fatigue was estimated by comparing the force generated by phrenic nerve-stimulated muscles with that generated by curare-treated field-stimulated muscles. DAP significantly increased force in nerve-stimulated muscles and, in addition, reduced the neurotransmission failure contribution to diaphragm fatigue. Thus DAP increases muscle force at low-to-intermediate stimulation frequencies, improves overall force and intratrain fatigue during 20-Hz intermittent stimulation, and reduces neurotransmission failure.

4-Aminopyridine↗
PubMedDate not supplied

The impact of fatigue in air medical and other types of operations: a review of fatigue facts and potential countermeasures.

Because of its effects on productivity and safety, fatigue is receiving increasing attention in a variety of settings, including aviation. Fatigue-related problems cost America an estimated $18 billion a year in terms of lost productivity, and fatigue-related drowsiness on the highways contributes to more than 1500 fatalities, 100,000 crashes, and 76,000 injuries annually. Furthermore, evidence is mounting that pilot and aircrew fatigue has been a causative factor in several aviation mishaps. Although substantial research has been conducted on the nature of fatigue and the effectiveness of various countermeasures, much of the relevant information may not be reaching those who need it most. The importance of obtaining adequate daily sleep and the efficacy of proper work/rest schedules, strategic napping, rest breaks, circadian-entrainment interventions, and other techniques should be emphasized in air medical training programs along with the more standard courses aimed at maintaining crew skills and improving flight safety. Once the facts are known, the aircrew's ability to control fatigue will enhance the productivity and safety of air ambulance operations.

Adult↗
PubMed1987

Changes in Bereitschaftspotential during fatiguing and non-fatiguing hand movements.

This study investigates the electroencephalographic Bereitschaftspotential (Bp) during muscular-fatiguing and non-fatiguing rhythmical hand contractions at 20%, 50%, and 80% maximum voluntary contraction (MVC). A feedback arrangement was provided so that subjects were able to adjust the force as required. The results confirm that Bp depends on force level. An increase in force results in a Bp increase. Further, they show that muscular-fatiguing contractions at 80% MVC are accompanied by an increased Bp. This could be the result of an increase in the central nervous activation required when preparing for motor activity with fatigued muscles. A decrease in Bp was observed during non-fatiguing repetitive hand contractions at 50% MVC. Possibly, the decrease reflects a decrease in subjects intentional involvement due to the monotony of the exercise. Repetitive movements at 20% MVC, which require a high degree of concentration and attention to adjust exactly to this very small force level, also result in an increased Bp, perhaps due to the higher intentional involvement. It may be concluded that the influence of muscular fatigue on Bp should be investigated with consideration of the psychological aspects of repetitive movements.

Adult↗
PubMed2002

Fatigue studies of high-palladium dental casting alloys: Part I. Fatigue limits and fracture characteristics.

The fatigue limits and fracture characteristics for a Pd-Cu-Ga alloy and a Pd-Ga alloy were studied. The alloys were cast into tensile test bars with gauge diameter of 3 mm and gauge length of 15 mm, and the surfaces of the castings were neither air-abraded nor polished after removal from the investment. Specimens were prepared from all-new metal (not previously melted), a combination of 50% new metal and 50% old metal (previously melted one time) and 100% old metal. The cast bars were subjected to heat treatment simulating the complete firing cycles for dental porcelain, and fatigued in air at room temperature under uniaxial tension-compression stress at 10 Hz and a ratio of tensile stress amplitude to compressive stress amplitude (R-ratio) of -1. The alloy microstructures and fracture surfaces were examined with a scanning electron microscope (SEM). Results showed that the fatigue limits at 2 x 10(6)cycles of the Pd-Cu-Ga and Pd-Ga alloys were approximately 0.20 and 0.15 of their 0.1% yield strength (YS) in tension, respectively. The fatigue resistance for specimens from both alloys containing 50% old metal and 50% new metal was comparable to that of specimens containing all-new metal, although this decreased dramatically for Pd-Cu-Ga alloy specimens containing all-old metal. The fatigue resistance of the Pd-Cu-Ga alloy subjected to heat treatment simulating the porcelain firing cycles was not adversely affected by remnants of the original as-cast dendritic microstructure that remained in the relatively large test specimens. A longer heat treatment than recommended by the manufacturer for the porcelain firing cycles is needed to completely eliminate the as-cast dendritic structure in these specimens. The Pd-Cu-Ga alloy exhibited superior fatigue resistance to the Pd-Ga alloy, which has an equiaxed-grain microstructure and lower yield strength.

Journal Article↗
PubMed1986

Is the change in intracellular pH during fatigue large enough to be the main cause of fatigue?

The intracellular pH of frog sartorius muscles exposed to an extracellular pH 8.0 (25 mM HCO3-, 1% CO2) was 6.9-7.1. Following a fatiguing stimulation period (one tetanic contraction per second for 3 min), the intracellular pH was 6.5-6.7. When similar experiments were repeated with frog sartorius muscles exposed to pH 6.4 (2mM HCO3-, 1% CO2), the intracellular pH was 6.8-6.9 at rest and 6.3-6.4 following fatigue. So, in both experiments the intracellular pH decreased by 0.4-0.5 pH unit during fatigue. When the CO2 concentration of the bathing solution was increased from 1 to 30%, the intracellular pH of resting muscles decreased from 7.0 to 6.2-6.3. Although the effect of CO2 on the intracellular pH was greater than the fatigue effect, the decrease in tetanic force with CO2 was less than 40%, while during fatigue the tetanic force decreased by at least 70%. Therefore in frog sartorius muscle the decrease in tetanic force during fatigue exceeds the decrease that is expected from just a change in intracellular pH.

Animals↗
PubMed1992

Motor units of medial gastrocnemius muscle in the rat during the fatigue test. II. Changes in the time course of sequential tetani of fatigue test.

Seventy motor units (MUs) of 3 types: fast fatigable (FF), fast resistant to fatigue (FR) and slow (S) were studied in medial gastrocnemius muscle of the rat. The fatigue test time course showed significant variability. It was found, that slow MUs, apart from greater resistance to fatigue, had less variable tetanic time course during the fatigue test than the fast MUs. The tetani of fast MUs were unfused with a marked sag. At the beginning of fatigue test the tension of fast motor units increased. The increase appeared to be greater and more rapidly developing in FF than in FR MUs. In the next part of fatigue test, when decrease in the tetanic tension was observed, the tetanic time course was changing in FF but not in FR MUs. During the first tetanus of fast MUs the sag exhibited a significant variability of its time course. In a proportion of fast MUs the sag appeared again when their tension was potentiated but in such a case it showed a different time course. The obtained results point to high degree of specialization of MUs in the studied muscle.

Animals↗
PubMed1996

Functional status in patients with chronic fatigue syndrome, other fatiguing illnesses, and healthy individuals.

BACKGROUND: Chronic fatigue syndrome (CFS) is a condition that may be associated with substantial disability. The Medical Outcomes Study Short-Form General Health Survey (SF-36) is an instrument that has been widely used in outpatient populations to determine functional status. Our objectives were to describe the usefulness of the SF-36 in CFS patients and to determine if subscale scores could distinguish patients with CFS from subjects with unexplained chronic fatigue (CF), major depression (MD), or acute infectious mononucleosis (AIM), and from healthy control subjects (HC). An additional goal was to ascertain if subscale scores correlated with the signs and symptoms of CFS or the presence of psychiatric disorders and fibromyalgia. DESIGN: Prospectively collected case series. SETTING: Patients with CFS and CF were seen in a university-based referral clinic and had undergone a complete medical and psychiatric evaluation. Other study subjects were recruited from the community to participate in research studies. PARTICIPANTS: The study included 185 patients with CFS, 246 with CF, 111 with AIM, and 25 with MD. There were 99 HC subjects. MEASURES: The SF-36 and a structured psychiatric interview were used. The SF-36 contains 8 subscales: physical, emotional, social, and role functioning, body pain, mental health, vitality, and general health- and a structured psychiatric interview. RESULTS: Performance characteristics (internal reliability coefficients, convergent validity) of the SF-36 were excellent. A strikingly consistent pattern was found for the physical functioning, role functioning, social functioning, general health, and body pain subscales, with the lowest scores in CFS patients, intermediate scores in AIM patients, and the highest scores in the HC subjects. The CFS patients had significantly lower scores than patients with CF alone on the physical functioning (P < or = 0.01), role functioning (P < or = 0.01), and body pain (P < or = 0.001) subscales. The emotional functioning and mental health scores were worst among those with MD. The presence of fibromyalgia, being unemployed, and increasing fatigue severity all were associated with additional functional limitations across multiple functional domains, with increasing fatigue appearing to have the greatest effect. CONCLUSIONS: The SF-36 is useful in assessing functional status in patients with fatiguing illnesses. Patients with CFS and CF have marked impairment of their functional status. The severity and pattern of impairment as documented by the SF-36 distinguishes patients with CFS and CF from those with MD and AIM, and from HC, but does not discriminate between CF and CFS.

Adult↗
PubMed1996

Fatigue in the chronic fatigue syndrome: a cognitive phenomenon?

What is the source of the perception of excessive fatigue in the chronic fatigue syndrome (CFS)? Studies of physiological response to aerobic activity, of muscle pathology and muscle function in CFS, are reviewed, and suggest that the subjective report of fatigue is not due to any peripheral impairment. In addition, current technological methods such as electroencephalography have failed to uncover the nature of any abnormality in the central motor unit. A physiological model which proposes that patients with CFS possess a reduced threshold for sensory fatigue signals is rejected, because it fails to account for recent findings. Instead, it is suggested that the perception of fatigue in CFS is enhanced by idiosyncrasies in cognitive processing. The implications of this view to our understanding of the perpetuation of CFS as a whole are explored.

Cognition↗
PubMedDate not supplied

Fatigue in chronic fatigue syndrome: a discourse analysis of women's experiential narratives.

Chronic fatigue syndrome (CFS) is a debilitating condition. Approximately 75% of sufferers are women. The etiology of CFS is debated, but remains inconclusive. "Fatigue" is ill defined and conceptually problematic. The international multidisciplinary literature on CFS reveals a paucity of studies on women. Qualitative research to analyze women's discourses on CFS is virtually absent. Eleven New Zealand women of European descent with experience of CFS were interviewed in depth. Within the complex facets of CFS, this article reports specifically on an analysis of discourses on "fatigue." The predominant theme that emerged was that fatigue is articulated as "lack" or absence, which is not representable as an identifiable entity in biomedical terms. Parallels with chronic pain are briefly drawn. We conclude that approaches to CFS must respond to the diverse and complex constructions of the experience of fatigue evident in women's narratives.

Activities of Daily Living↗
PubMed1994

Cytokine production and fatigue in patients with chronic fatigue syndrome and healthy control subjects in response to exercise.

We have studied the relationship between the cytokine production induced in vivo by prolonged isometric exercise and the symptom complex marked by fatigue in patients with chronic fatigue syndrome (CFS). Twelve male patients and 13 matched male control subjects undertook an isometric hand-grip exercise protocol utilizing dynamometers. Subjects undertook 30 minutes of exercise, for which the target force was set at 40% of the maximal voluntary contraction and the duty cycle was 50%. Prior to, during, and for 24 hours following the exercise, blood samples were collected and assayed for the presence of cytokines, including interferon-gamma and interferon-alpha, interleukin-1 beta, and tumor necrosis factor-alpha. At those times subjects also completed the Profile of Mood States (POMS) questionnaire, which served as a measure of changes in subjective fatigue. No significant alteration in the level of any of the cytokines in the plasma of patients or control subjects was detected before, during, or after exercise. Surprisingly, the patients' levels of fatigue, depression, and confusion, as measured by the POMS, decreased in response to the exercise. These data do not confirm the presence of an immunologic process correlating with the exacerbation of fatigue after exercise experienced by patients with CFS. Limitations in the study design and in the sensitivity of the cytokine assays may have affected our results.

Adult↗
PubMed1999

Associations between perfectionism, mood, and fatigue in chronic fatigue syndrome: a pilot study.

This study investigated possible associations between perfectionistic personality traits, mood, and fatigue in chronic fatigue syndrome (CFS). Forty CFS sufferers referred to tertiary care and 31 control healthy subjects completed the Multidimensional Perfectionism Scale (MPS), Chalder Fatigue Questionnaire, and Hospital Anxiety and Depression (HAD) scale. Total perfectionism scores did not correlate with fatigue, anxiety, or depression in either group. Other-oriented MPS scores were significantly lower among CFS sufferers (p = .0019), especially women, and correlated negatively with physical fatigue levels overall (R = -0.27, p = .02). Total and socially prescribed MPS scores correlated with age for the CFS group alone (p = .05). Possible reasons why this study did not confirm a positive association between perfectionism and CFS are discussed. The finding that CFS sufferers set lower standards and have lower expectations for significant others may have implications for rehabilitation and recovery from this disorder.

Adult↗
PubMedDate not supplied

Sleep disturbances and fatigue in women with fibromyalgia and chronic fatigue syndrome.

OBJECTIVE: To determine the relationship between sleep disturbances and fatigue in women with fibromyalgia (FM) and those with chronic fatigue syndrome (CFS) and to assess whether any differences existed between the two groups. DESIGN: Descriptive comparative. SETTING: Community program on chronic fatigue syndrome and related disorders. PARTICIPANTS: Sixty-three women who attended the program; 13 had CFS, and 50 had FM. MAIN OUTCOME MEASURES: A moderately strong relationship between fatigue and sleepiness was found (r = .63, p < .01). Trouble staying asleep was the highest rated sleep disturbance, and fatigue was the most common subjective feeling reported. Women with CFS reported significantly more trouble staying asleep than women with FM, t(61) = 1.81, p < .03. CONCLUSIONS: Data from this study support that women with FM and CFS encounter problems sleeping. Clinicians are encouraged to assess women with FM and CFS for their quality of sleep rather than amount of sleep. Researchers are encouraged to continue study of sleep disturbances in women with FM and CFS to improve understanding of the disturbances and to test the effectiveness of sleep interventions.

Adult↗
PubMed2006

Chronic fatigue syndrome-like caseness as a predictor of work status in fatigued employees on sick leave: four year follow up study.

OBJECTIVE: To assess whether CFS-like caseness (meeting the criteria for chronic fatigue syndrome (CFS)) predicts work status in the long term. METHODS: Prospective study in a sample of fatigued employees absent from work. Data were collected at baseline and four years later, and included CFS-like caseness and work status (inactive work status and full work incapacity). RESULTS: CFS-like cases at baseline were three times more likely to be unable to work at follow up than fatigued employees who did not meet CFS criteria at baseline (ORs 3-3.3). These associations grew even stronger when demographic and clinical confounders were controlled for (ORs 3.4-4.4). CONCLUSION: A CFS-like status (compared to non-CFS fatigue) proved to be a strong predictor of an inactive work status and full work incapacity in the long term. Since little is known about effective interventions that prevent absenteeism and work incapacity or facilitate return to work in subjects with chronic fatigue, there is a great need for powerful early interventions that restore or preserve the ability to work, especially for workers who meet criteria for CFS.

Absenteeism↗
PubMed1999

[The relationship among subjective symptoms of fatigue, subjective fatigue feeling, and life habits of high school and college students].

The relationship among subjective symptoms of fatigue, subjective fatigue feeling, and life habits of high school and college students. The purpose of this study was to examine the relationship among subjective symptoms of fatigue (SSF), subjective fatigue feeling (SFF), life habits (behavioral patterns (BP) and life-style consciousness (LC)) in male students. A questionnaire on SSF, SFF, fatigue content, BP and LC was administered to 1802 male students aged 15-20 yr, and data from 1792 properly completed questionnaires was analyzed. The results were: 1) Students experience high SFF from daily activity. Students with a higher SFF tend to have more complaints of SSF, especially symptoms of languor, but the relationship between SFF and symptoms of irritation and physical disintegration are low. 2) Relationships between SFF and BP and LC are relatively low, except for physical condition. Even if the BP is successful, student's SFF is relatively high. 3) Subjective degree of health and physical condition relate highly to SSF. Exercise habits relate to loss of vigor, dietary habits to languor, loss of vigor, drowsiness and a decrease in concentration, and LC to SSF except for languor. It was inferred that SSF is influenced by BP and LC.

Adolescent↗
PubMed2003

Muscle recovery from a short fatigue test and consequence on the reliability of EMG indices of fatigue.

The purpose of the present study was to evaluate if rest intervals of 10 or 15 min allow the back muscles to recover completely, from an electromyographic (EMG) point of view, after performing a fatiguing contraction. Twelve healthy males stood in a dynamometer with the trunk in a vertical position and performed three trunk extension fatiguing trials (30 s contractions sustained at 75% of the maximal voluntary contraction) separated successively by a 15 min (between trial 1 and 2) and a 10 min (between trial 2 and 3) rest period. The EMG signals from four pairs of back muscles were collected at 2,048 Hz with active surface electrodes. Different EMG indices computed from the temporal and frequency domains of the EMG signal were considered to evaluate muscular fatigue and recovery from trial 1 to trial 2 and from trial 2 to trial 3. No significant differences (one-way ANOVAs between the three trials, alpha=0.05) were obtained for the different EMG indices computed. The percentage of variance explained by the inter-trial effect was none in most cases, corroborating that no systematic error was present between the trials and suggesting that complete muscle recovery was allowed with 10 or 15 min rest periods. These results support the use of rest periods of 10 to 15 min between multiple fatigue tests, at least for back muscles and for high intensity short duration fatigue tasks as the one used in the present study.

Adult↗
PubMed2005

Effects of acupuncture on heart rate variability in normal subjects under fatigue and non-fatigue state.

The objective of this study was to assess the effects of acupuncture applied at Hegu (LI 4) points and Neiguan (PC6) points on heart rate variability (HRV) in normal subjects under fatigue and non-fatigue states using power spectral analysis. Twenty-nine normal male subjects were randomly divided into three groups. Subjects in Group A and Group B performed a simulated driving task for 3 h and acupuncture needles were then inserted perpendicularly into the LI 4 points in the middle of the dorsal thenar muscle and PC 6 points situated between the tendons of the palmaris longus and carpi radialis muscles for 15 min for Group A but inserted subcutaneously to the acupuncture points for Group B as a control. Acupuncture needles were directly inserted perpendicularly into the LI 4 points and PC 6 points for 15 min for Group C. Stimulations of the acupuncture points induced a significant decrease in heart rate (HR), HRV total power (TP), low frequency (LF) power and ratio of low frequency to high frequency (LF/HF), and a significant increase in the HF power in normalized units (NU) during the post stimulation period in fatigue state (P<0.05). Stimulation of acupuncture points resulted in a significant increase both in the LF power and HF power in absolute units (AU) (P<0.05) but no significant change in NU was found during the post stimulation period in non-fatigue state. It was concluded that the modulating effect of acupuncture on heart rate variability not only depended on the points of stimulation such as acupuncture or non-acupuncture points but also on the functional state of the subject, namely whether the subjects are in a state of fatigue or not.

Acupuncture Points↗
PubMed2006

Measuring fatigue in Parkinson's disease: a psychometric study of two brief generic fatigue questionnaires.

This study evaluated and compared the measurement properties of the 13-item Functional Assessment of Chronic Illness Therapy-Fatigue Scale (FACIT-F) and the 9-item Fatigue Severity Scale (FSS) in 118 consecutive Parkinson's disease (PD) patients, using traditional and Rasch measurement methodologies. Both questionnaires exhibited excellent data quality and reliability (coefficient alpha>or=0.9), and acceptable rating scale functionality, and both discriminated between fatigued and nonfatigued patients. Factor and Rasch analyses provided general support for unidimensionality of both FACIT-F and FSS, although they do not appear to measure identical aspects of fatigue. No signs of differential item functioning (DIF) were found for the FACIT-F, whereas potential age DIF was detected for two FSS items. These results support the measurement validity of both questionnaires in PD, although the FACIT-F displayed better measurement precision and modest psychometric advantages over the FSS. Availability of psychometrically sound fatigue measures that are applicable across disorders provides a sound basis for advancing the understanding of this common and distressing complaint.

Aged↗
PubMedDate not supplied

DUFS and DEFS: development, reliability and validity of the Dutch Fatigue Scale and the Dutch Exertion Fatigue Scale.

The purpose of this study among patients with chronic heart failure (n = 138) was to develop and test both the Dutch Fatigue Scale (DUFS) and the Dutch Exertion Fatigue Scale (DEFS). Psychometric testing of these scales included measurement of internal consistency, construct validity and criterion-related validity. Statistical analyses of both scales showed sufficient reliability and validity. The DUFS (scale coefficient H = 0.48; Rho = 0.80; KR-20 = 0.79) is suitable as a measurement instrument for the diagnosis of fatigue and makes it possible to compare results of fatigue on the level of groups of patients. The DEFS (scale coefficient H = 0.61; Rho = 0.91; Cronbach's alpha = 0.91) can be used in clinical practice for the measurement of patients' exertion fatigue.

Adult↗