Training-induced changes in skeletal muscle Na+-K+ pump number and isoform expression in rats with chronic heart failure

The mechanisms responsible for the decrements in exercise performance in chronic heart failure (CHF) remain poorly understood, but it has been suggested that sarcolemmal alterations could contribute to the early onset of muscular fatigue. Previously, our laboratory demonstrated that the maximal number of ouabain binding sites (B(max)) is reduced in the skeletal muscle of rats with CHF (Musch TI, Wolfram S, Hageman KS, and Pickar JG. J Appl Physiol 92: 2326-2334, 2002). These reductions may coincide with changes in the Na(+)-K(+)-ATPase isoform (alpha and beta) expression. In the present study, we tested the hypothesis that reductions in B(max) would coincide with alterations in the alpha- and beta-subunit expression of the sarcolemmal Na(+)-K(+)-ATPase of rats with CHF. Moreover, we tested the hypothesis that exercise training would increase B(max) along with producing significant changes in alpha- and beta-subunit expression. Rats underwent a sham operation (sham; n = 10) or a surgically induced myocardial infarction followed by random assignment to either a control (MI; n = 16) or exercise training group (MI-T; n = 16). The MI-T rats performed exercise training (ET) for 6-8 wk. Hemodynamic indexes demonstrated that MI and MI-T rats suffered from severe left ventricular dysfunction and congestive CHF. Maximal oxygen uptake (Vo(2 max)) and endurance capacity (run time to fatigue) were reduced in MI rats compared with sham. B(max) in the soleus and plantaris muscles and the expression of the alpha(2)-isoform of the Na(+)-K(+)-ATPase in the red portion of the gastrocnemius (gastrocnemius(red)) muscle were reduced in MI rats. After ET, Vo(2 max) and run time to fatigue were increased in the MI-T group of rats. This coincided with increases in soleus and plantaris B(max) and the expression of the alpha(2)-isoform in the gastrocnemius(red) muscle. In addition, the expression of the beta(2)-isoform of the gastrocnemius(red) muscle was increased in the MI-T rats compared with their sedentary counterparts. This study demonstrates that CHF-induced alterations in skeletal muscle Na(+)-K(+)-ATPase, including B(max) and isoform expression, can be partially reversed by ET.

Patient factors related to the presentation of fatigue complaints: results from a women's general health care practice

The aim of this study was to examine which patient-related factors predicted: (1) fatigue, (2) the intention to discuss fatigue and (3) the actual discussion of fatigue during consultation with a GP in a women's general health care practice. Patients were asked to complete two questionnaires: one before and one after consultation. The patient-related factors included: social-demographic characteristics; fatigue characteristics; absence of cognitive representations of fatigue; nature of the requests for consultation; and other complaints. Some 74% of the 155 respondents reported fatigue. Compared to the patients that were not fatigued, the fatigued patients were more frequently employed outside the home, had higher levels of general fatigue, and a higher need for emotional support from their doctor. A minority (12%) intended to discuss fatigue during consultation. Of the respondents returning the second questionnaire (n = 107), 22% reported actually discussing their fatigue with the GP while only 11% had intended to do so. In addition to the intention to discuss fatigue during consultation, the following variables related to actually discussing fatigue: living alone, caring for young children, higher levels of general fatigue, absence of cognitions with regard to the duration of the fatigue, and greater psychological, neurological, digestive, and/or musculoskeletal problems as the reason for consultation. Fatigue was found to be the single reason for consultation in only one case. It is concluded that fatigue does not constitute a serious problem for most patients and that discussion of fatigue with the GP tends to depend on the occurrence of other psychological or physical problems and the patient's social context.

What is behind "I'm so tired"? Fatigue experiences and their relations to the quality and quantity of external stimulation

In the present study, it is hypothesized that both low quality and high quantity of external stimulation are related to elevated levels of fatigue. This is proposed by the Quality-Quantity model for understanding fatigue (QQuF model). The relations between the quality and quantity of external information and the Multidimensional Fatigue Inventory (MFI-20) are examined. Moreover, the role of depression (measured with the CES-D) in relation to the QQuF model is explored. The results show low quality of external stimulation, that is, low "attractiveness of external stimulation," relating to all five dimensions of fatigue. A high quantity of external stimulation, that is, high "experienced overload," related primarily to general and mental fatigue. The QQuF model was only slightly moderated by depression, but depression directly and strongly related to all dimensions of fatigue. It is concluded that fatigue related to low quality of external stimulation can be distinguished from fatigue related to a high quantity of external stimulation. This distinction is useful when considering theoretical issues and treatment of fatigue.

Complaints of fatigue: related to too much as well as too little external stimulation?

Fatigue has been acknowledged as a widespread problem associated with a variety of factors. In the present paper, we attempt to explain fatigue complaints on the basis of Pennebaker's (1982) "competition of cues" notion. Competition of cues suggests that both extremely low and extremely high levels of external stimulation in daily life may be related to relatively higher frequencies of complaint. The dimensional structure of external stimulation is first explored and then the shape of the relation between external stimulation (i.e., stimuli perceived in daily life) and fatigue was studied in a sample of 777 general-practice patients. Other risk factors for fatigue and moderating factors are also taken into consideration. Results show that quantity and quality of external stimulation can be distinguished. Both high quantity (high "experienced overload") and low quality (low "attractiveness of external stimulation") are related to higher fatigue frequencies. "Experienced overload" is a particularly strong predictor, in addition to "perceived health" of fatigue complaints. It is concluded that the "quality-quantity model for understanding fatigue" proposed here highlights psychological factors important for any theoretical framework of fatigue.

Gender differences in fatigue: biopsychosocial factors relating to fatigue in men and women

BACKGROUND

Fatigue is a common problem, which is found more frequently among women than men. To date, neither the etiology of fatigue nor the factors that explain the gender difference in its incidence are still fully understood.

METHODS

In a sample of men (n = 4,681) and women (n = 4,698) (age range, 15-64 years) in the Dutch National Survey of Morbidity and Interventions in General Practice, the gender differences in the underlying biological, psychological, and social factors of fatigue were analyzed.

RESULTS

Both general and gender-specific factors were recognized. Men and women who experience complaints of fatigue appeared to be younger and more highly educated. They had more acute health complaints and more psychosocial problems and also showed a lower level of perceived health. Among women, only gender-specific biological complaints and psychosocial problems were related to fatigue. In addition, relevant sociodemographic variables included taking care of young children and being employed. Among men, fatigue was particularly related to having handicaps and severe chronic complaints. Taking care of young children did not make a difference in the male sample.

CONCLUSIONS

Fatigue can only be adequately understood in a multicausal model with biomedical and psychosocial factors. Complaints of fatigue are too often ignored in general practice. By adopting a patient-centered style of communication, physicians can acquire a more complete picture of the patients' fatigue.

General practitioners' attributions of fatigue

In this paper general practitioners' (GPs') somatic-psychosocial attributions of fatigue are examined. The attribution process during medical consultations was studied by relating the GPs' judgements of the somatic-psychosocial character of their patients' fatigue to patient-related characteristics, on the one hand, and medical-consultation characteristics on the other hand. The study was based on 2097 contact registrations from the Dutch National Study of Morbidity and Intervention in General Practice by the NIVEL (Netherlands Institute of Primary Health Care). In order to explain the GPs' attributions, patient-related characteristics were added stepwise in a multiple regression analysis. Sociodemographic characteristics explained only 1.8% of the variance. Other complaints explained an additional 14.3% with psychosocial complaints being most influential. Knowledge of an underlying disease/problem explained an additional 9.9% of the variance. All of the characteristics together explained 26.0% of the attributions by the GPs. More psychosocially-attributed fatigue was found to correlate with consultations characterized by less physical examination, more diagnostic procedures to reassure, fewer diagnostic procedures to discover underlying pathology, more counselling, less medical treatment, less prescription and a longer duration than consultations with more somatically attributed fatigue. It is concluded that GPs do not discriminate between social groups when attributing fatigue to either somatic or psychosocial causes. The presence and character of other complaints and underlying diseases/problems, rather, relate to the GPs' somatic psychosocial attributions, which are then associated with particular aspects of the consultation.

Integration of coping and social support perspectives: implications for the study of adaptation to chronic diseases

In this article, empirical studies dealing with the relationship between coping and social support are discussed in order to identify promising themes for research on adaptation to chronic diseases. Although only few studies deal with this issue explicitly, the review reveals that four ways to study the relationship between coping and social support can be distinguished: (a) seeking social support as a coping strategy; (b) social support as a coping resource; (c) social support as dependent on the way individual patients cope; and (d) coping by a social system. It is argued that all four ways of integrating coping and social support contribute to a better understanding of adaptation to chronic diseases. However, exploring the interrelatedness of both concepts by studying social support as a coping resource and social support as dependent on the patient's own coping behavior appear to be especially fruitful in the short term, as they: (a) provide a better insight in the social determinants of coping, and (b) may help to clarify the way social support affects health and well-being.