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. Author manuscript; available in PMC: 2008 Aug 11.
Published in final edited form as: J Adv Nurs. 2007 May 1;58(5):503–512. doi: 10.1111/j.1365-2648.2007.04293.x

Using a conceptual model in nursing research - mitigating fatigue in cancer patients

Victoria Mock 1, Christine St Ours 2, Sue Hall 3, Amy Bositis 4, Miriam Tillery 5, Anne Belcher 6, Sharon Krumm 7, Ruth McCorkle 8
PMCID: PMC2505113  NIHMSID: NIHMS59325  PMID: 17484740

Abstract

Aim

This paper is a discussion of the use of the Levine Conservation Model to guide the investigation of an exercise intervention to mitigate cancer-related fatigue.

Background

Researchers use conceptual models or theoretical frameworks to provide an organizing structure for their studies, to guide the development and testing of hypotheses, and to place research finding within the context of science. Selection of an appropriate and useful framework is an essential step in the development of a research project.

Method

A descriptive approach is used to present the components of the conceptual model and details of the articulation of the study intervention and outcomes with the model.

Findings

The Levine Conservation Model provided a useful framework for this investigation, conducted in 2002-2006, of the effects of exercise on fatigue and physical functioning in cancer patients. The four conservation principles of the model guided the development of the exercise intervention, the identification of salient outcomes for patients, and the selection of appropriate instruments to measure study variables. The model is also proving useful in the analysis and interpretation of data in relation to the conservation principles.

Conclusion

Use of an appropriate conceptual model facilitates the design and testing of theory-based interventions and the development of science to support nursing practice.

Keywords: cancer, fatigue, Levine Conservation Model, nursing, randomized controlled trial, research, theoretical frameworks

Introduction

Nurse researchers regularly use conceptual models to design and conduct their investigations. In this paper, we provide a dynamic example from a nursing study which enrolled 138 participants between 2002 and 2006. The purpose of this paper is to describe the use of a nursing conceptual model, the Levine Conservation Model (Levine 1996), to guide the development and implementation of a randomized clinical trial. The trial tests the effects of exercise in mitigating cancer-related fatigue in individuals being treated with radiation therapy or adjuvant chemotherapy following a cancer diagnosis.

A conceptual model or theoretical framework provides a coherent, unified and orderly way of envisioning related events or processes relevant to a discipline (Fawcett 2005). In research, a framework illustrates the overall conceptual design of the study. The terms ‘conceptual model’ and ‘theoretical framework’ are often used interchangeably, but a theoretical framework generally incorporates at least part of a specific theory as the basis for a study. In addition, a theoretical framework often includes propositional statements describing the relationships among variables and has received more testing than the more tentative conceptual model (Polit & Beck 2004).

The most common use of conceptual models is to provide an organizing structure for the research design and methods. A second purpose is to guide the development and testing of interventions and hypotheses based on the tenets of the theory. A third function is to explain the study results and place the findings within the context of science in a specific field of investigation. The interpretation of findings flows from the conceptualization represented by the framework (Radwin & Fawcett 2002, Polit & Beck 2004).

At its most fundamental, a conceptual model is composed of concepts and the theoretical linkages between them which together describe a particular relationship between two or more concepts. Concepts are connected in a theory by verbal or mathematical statements called propositions. Research hypotheses are derived from these propositions, in that hypotheses describe a presumed relationship between two or more measures of concepts in the conceptual model (Fawcett 1978). Testing hypotheses in the context of a study can be expected to yield information about the validity of the propositions in the underlying theory, and thus the relationships between the concepts under investigation. This information can be added to the evidence in support (or in refutation) of the theory and builds the science related to the concepts being studied (Fawcett 2005).

Background

Cancer-related fatigue

Cancer-related fatigue is defined by the National Comprehensive Cancer Network (NCCN) as a distressing persistent, subjective sense of tiredness or exhaustion related to cancer or cancer treatment that is not proportional to recent activity and interferes with usual functioning (NCCN 2006). Fatigue is an almost universal symptom in patients receiving cytotoxic chemotherapy, radiation therapy, bone marrow transplantation, or treatment with biological response modifiers (Wagner & Cella 2004). This problem, which affects 70-100% of cancer patients, has been exacerbated in recent years by the increased use of fatigue-inducing multimodal treatments and of dose-dense, dose-intense protocols (Ahlberg et al. 2003). In patients with metastatic disease, the prevalence of cancer-related fatigue exceeds 75%, and cancer survivors report that fatigue is a disruptive symptom months or even years after treatment ends (Andrykowski et al. 1998, Broeckel et al. 1998, Bower et al. 2000). Patients perceive fatigue to be the most distressing symptom associated with cancer and its treatment, more distressing even than pain or nausea and vomiting, which in the case of most patients can be managed effectively by medication (Curt et al. 2000). Compared with the fatigue of healthy individuals that resolves with adequate rest and sleep - the fatigue of cancer patients often remains after a period of rest or sleep, is of greater magnitude and persistence, is more disruptive to activities of daily living, and has a more negative affective impact (Glaus et al. 1996). Fatigue in cancer patients has been under-reported, underdiagnosed and undertreated. The most important effect of persistent cancer-related fatigue is altering quality of life, as cancer patients become too tired to participate fully in valued roles and activities (Dean & Ferrell 1995).

Management of cancer related fatigue (CRF) is important in that high levels of fatigue may affect functional status and the ability to tolerate cancer treatment. Research reports indicate that fatigue may have a profound effect on functional status (Given et al. 2001, Nail 2002) and it is uncertain whether patients regain full functioning when treatment is over (Bower et al. 2000). Furthermore, if fatigued patients cannot tolerate their cancer treatment or must choose between treatment and quality of life, control of their malignancy may be compromised (Malik et al. 2001). Healthcare professionals have been challenged in their efforts to help patients manage distressing symptoms and remain as fully engaged in life as possible. However, increasing evidence indicates that exercise training is effective in managing the fatigue associated with cancer diagnosis and treatment (Winningham 2001, Stricker et al. 2004, Schmitz et al. 2005).

Levine Conservation Model

Selecting an appropriate conceptual model or theoretical framework is an important step in research development because it provides a pattern of reasoning to guide the research. The Levine Conservation Model was adopted for the study discussed here because it includes principles that help explain cancer-related fatigue and support exercise as a potential intervention for the fatigue (Levine 1973). Although in our earlier work we had used a more general adaptation model (Mock et al. 1994, 1997), our team first adopted the Levine Conservation Model for a pilot project studying cancer-related fatigue in 1995-1996 (Mock et al. 1998, 2001); this was then followed by a multi-site clinical trial, ‘Fatigue in Cancer Patients: An Exercise Intervention’, in 1996-2001 (Mock et al. 2005). Data from both the pilot study and larger clinical trial supported the model and demonstrated its usefulness as a framework for the investigation of the effects of exercise on fatigue and physical functioning in cancer patients.

Levine’s Conservation Model proposes a general mechanism underlying biobehavioural symptoms, such as fatigue, that necessitates a response or adaptation from the individual to maintain unity and integrity (Levine 1996). According to Levine, the goal of the individual is conservation or preserving an integrated and balanced whole (Levine 1973). The four conservation principles that underlie this model are conservation of energy, conservation of structural integrity, conservation of personal integrity and conservation of social integrity (Levine 1989). When environmental challenges occur, as in the case of cancer and its treatment, the individual begins a multidimensional process of adaptation to maintain life and conserve individual integrity. Nursing interventions are aimed at promoting and supporting this adaptation.

The diagnosis of cancer and the subsequent surgical, chemotherapy and radiotherapy treatments produce an altered biochemical environment (threat to structural integrity) and create psychosocial distress related to survival and quality of life (threats to personal and social integrity). The processes of diagnosis and treatment are often lengthy and emotional responses are energy-depleting. When environmental and psychological stress is prolonged, chronic fatigue behaviours are manifested. Cancer patients typically reduce their usual levels of physical activity and this reduction, if prolonged, inevitably leads to changes in structural and functional integrity and a reduced tolerance for normal activity. This process can threaten personal and social integrity by affecting emotional equilibrium, social roles and health-related quality of life.

Evidence is accumulating that exercise interventions have the potential to assist the individual in adapting to the physical and psychological stress of cancer and related treatments (Dimeo et al. 2004, Stricker et al. 2004, Galvao & Newton 2005, Knols et al. 2005, Schmitz et al. 2005). Exercise can help to maintain or increase capacity for physical activity and activity tolerance, resulting in performance of daily activities with less fatigue (Lucia et al. 2003, ASCM 2005). Exercise can also improve emotional responses (Mock et al. 1997, Segar et al. 1998, Dimeo et al. 1999) [Levine Model: personal integrity] and provide energy for social interactions (Holley & Borger 2001, Mock et al. 2001) (Levine Model: social integrity). Many studies of cancer patients and survivors have demonstrated the clinical benefits of regular exercise - both aerobic exercise and strength training programmes (Dimeo 2001, Segal et al. 2001, 2003, Courneya et al. 2003a, 2003b). Although the studies have not been uniformly rigorous, the overall benefits have been substantiated in meta-analyses and systematic reviews (Knols et al. 2005, Schmitz et al. 2005, Conn et al. 2006, McNeely et al. 2006, Mitchell et al. 2007).

The study

Overview

The purpose of the ongoing study described here was to determine the effects of a nurse-directed, moderate-intensity, home-based exercise programme to mitigate fatigue and maintain physical functioning in individuals receiving cancer treatment. The study design employed is a randomized controlled clinical trial. The enrolment eligibility criteria require that patients be 21 years of age or older with a newly diagnosed cancer, histologically staged at 0, I, II or III. Patients must be scheduled to receive chemotherapy, radiation therapy, or both as their initial treatment, must show no evidence of metastatic disease, and be free of concurrent health problems/disabilities that would limit their ability to participate in an exercise programme. They must not currently be exercising more than three times per week, for a total of 120 minutes. One-hundred and thirty-eight patients scheduled to receive chemotherapy or radiation therapy at one of four academic cancer centre-affiliated treatment sites have been enrolled. The study was approved by the University Institutional Review Board.

Once eligibility is determined and informed consent is obtained, patients are randomized into exercise (EX) or usual care (UC) groups. Patients assigned to the EX group are given a written prescription for an individualized, symptom-limited, home-based walking and muscle-strengthening exercise programme that they maintain throughout their cancer treatment. These patients are taught the programme with the assistance of a booklet and video describing the walking exercise programme and instructional materials that detail the muscle-strengthening component. The walking exercise programme that extends from the beginning of cancer treatment through treatment completion is a brisk, incremental 20- to 30-minute walk, followed by 5 minutes of slow walking (cool-down). The muscle-strengthening programme consists of 3-5 minutes of warm-up and one set of 10-20 repetitions with elastic resistance bands for each of the six exercises prescribed.

Patients in the UC group receive standard care as provided by their oncology care team and no prescribed exercise programme. Patients in both groups receive phone calls every 2 weeks from a research nurse. During these calls, EX group patients are assessed in terms of the appropriateness of their walking and muscle-strengthening prescription, are coached on their exercising, and have their walking or muscle-strengthening prescription revised as needed. Patients in the UC group are contacted on the same schedule to provide an attentional control for the study and are assessed in terms of their response to cancer treatment and changes in current activity level. Patients in both groups are referred to their oncology care team regarding issues related to side effects or symptom management and are given an educational pamphlet.

Managing fatigue

All patients are assessed by treadmill, dual-energy X-ray absorptiometry scan, muscle strength test, self-reported activity level and symptom questionnaires at pretest (at baseline before beginning cancer treatment) and again at post-test (following the completion of treatment). Activity level is measured objectively by use of pedometer and accelerometer for 1 week at pretest, mid-test and post-test. At mid-treatment, fatigue and other symptoms are assessed in both groups. All patients are asked to complete a weekly log during their treatment to record daily fatigue levels. The weekly log for the EX group also includes a record of minutes walked, pulse rate, perceived exertion, pedometer values and comments. Follow-up data are collected for each patient at 1-, 3- and 6-month time points after completion of cancer treatment. At these follow-up points, the questionnaires quantify fatigue and other symptoms as well as level of physical functioning. At study end, groups will be compared by repeated measures of analysis, anova and ancova. Multivariate regression procedures will be used to determine the predictors of cancer-related fatigue and of adherence to exercise during cancer treatment.

This study has been designed to test the efficacy of a low-cost, self-care health-promotion activity in mitigating fatigue, the most common and distressing symptom of cancer treatment. The biobehavioural outcomes include both subjective, self-reported symptoms and objective, physiological changes in physical capacity and performance.

Using the Levine Conservation Model to guide the study

Once the Levine Conservation Model was chosen to guide this study, the study variables were carefully selected to be congruent with the model, as were the tools used for data collection and the intervention being tested. This approach ensured that appropriate outcome variables were used in the evaluation, which includes measurement of the four components of this particular model. Also, it became clear that all four components should be addressed in implementing the intervention, as well as in interpreting the study data.

Aims

Four aims and two hypotheses were identified for the study; these flow from propositional statements identified for the Levine Conservation Model:

  • Aim 1

     To test the hypothesis that patients receiving radiation therapy or adjuvant chemotherapy for prostate, breast, or colorectal cancer who participate in a regular exercise programme demonstrate significantly lower levels of fatigue, sleep disturbance, and emotional distress, with significantly higher levels of physical functioning and quality of life compared to similar patients who do not participate in regular exercise. Propositional statement: Regular exercise decreases fatigue, sleep disturbance, and emotional distress as well as increases physical functioning and health-related quality of life.

  • Aim 2

     To test the hypothesis that the amount of change in physical functioning from baseline to post-2 (as measured by the treadmill test, body composition evaluation, and self-reported exercise/activity level) is correlated with the amount of change in levels of fatigue, difficulty sleeping, emotional distress, and quality of life. Propositional statement: There is a significant relationship between changes in levels of physical functioning and changes in levels of fatigue, difficulty sleeping, emotional distress, and quality of life.

Two secondary aims were identified for the study:

  • Aim 3

     To determine factors that predict patients at high risk for cancer treatment-related fatigue.

  • Aim 4

     To determine factors that predict adherence and non-adherence to the exercise intervention.

Because these were exploratory aims, no hypotheses were developed for them.

Instruments

The four components of the Levine Conservation Model and how they were incorporated into instrument selection are shown in Table 1. Conservation of energy is represented by the main study variable fatigue as well as by the sleep variable, which has obvious implications for both fatigue and conservation of energy. The study uses the NCCN definition of fatigue and fatigue is measured by the modified Piper Fatigue Scale, which assesses overall fatigue and four dimensions of subjective fatigue: temporal, severity, affective and sensory (Piper et al. 1998). In addition, subjects record daily self-reported fatigue levels in logs that are mailed every week to the study team. A simple measure of rating fatigue on a scale of 0 (no fatigue) to 10 (a great deal of fatigue) is used on the daily logs to decrease respondent burden. The Profile of Mood States fatigue subscale and the fatigue item on the Symptom Distress Scale (SDS) provide additional measures of fatigue. Sleep quality and quantity are measured by the Pittsburgh Sleep Quality Index (Buysse et al. 1989).

Table 1.

Components of the Levine Conservation Model as framework for the study variables and instruments (from consultation with Jacqueline Fawcett, PhD, RN, FAAN, 1996)

Conceptual framework concepts Conservation of energy Conservation of structural integrity Conservation of personal integrity Conservation of social integrity
Study variables Fatigue
Sleep		 Physical functioning Emotional distress
Quality of life		 Social functioning
Study instruments Piper Fatigue Scale
Fatigue level 0-10 Scale on daily log
Profile of Mood States - Fatigue Subscale
Symptom Distress Scale
Pittsburgh Sleep Quality Index		 Medical Outcomes Study - Physical Functioning Subscale
VO2 Max
Pedometer
Accelerometer
Physical Activity Questionnaire		 Medical Outcomes Study - Emotional Functioning Subscale
Profile of Mood States
Symptom Distress Scale		 Medical Outcomes Study - Social Functioning Subscale
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Conservation of structural integrity is represented by physical functioning, defined as the ability to ambulate and to perform normal activities of daily living, and is measured by maximum functional capacity [using a modified Balke Protocol Stress Test (ACSM 2005)] as well as by pedometer and accelerometer, which measure steps taken and speed of movement. Self-perceived physical functional ability is measured by the Medical Outcome Study-36 Physical Functioning Subscale (Ware & Sherbourne 1992). The self-reported level of weekly exercise is quantified at baseline and post-test by the Physical Activity Questionnaire, which converts daily activity into metabolic equivalents of oxygen consumption (Kohl et al. 1988).

Conservation of personal integrity is represented by the study variables of emotional distress and quality of life. Emotional distress is defined as an uncomfortable mood state or psychological response and is measured by the Profile of Mood States Scale (POMS). The short-form POMS measures subjects’ mental/psychological status (Shacham 1983) on subscales that assess six emotional dimensions: anxiety, depression, anger, vigour, fatigue and confusion. An additional measure of emotional distress is provided by the anxiety and depression items from the SDS. Quality of life is defined as self-assessment of satisfaction with the physical, social and emotional aspects of one’s life and is measured by the Medical Outcome Study 36-item Short Form Health Form (MOS SF-36, distributed by RAND). The MOS SF-36 is a multi-item scale that includes eight health concepts: physical functioning, social functioning, role functioning-physical, bodily pain, general mental health, role functioning-emotional, vitality and general health perceptions (Ware & Sherbourne 1992).

Conservation of social integrity is represented by social functioning which, although not a major variable in the study, is measured by the MOS-SF Social Functioning Subscale. Symptom experience, defined as the totality of uncomfortable perceptions related to the cancer diagnosis and treatment, is considered an inherent component of both physical functioning and emotional distress and is measured by the SDS (McCorkle & Young 1978), which assesses the degree of distress associated with 11 symptoms frequently experienced by cancer patients. Some instruments, such as the MOS and SDS, are comprehensive and able to measure several of the study outcomes.

The intervention

Prolonged exposure to the environmental challenges of cancer diagnosis and treatment may erode the individual’s energy resources. According to the NCCN Fatigue Practice Guidelines, exercise has the strongest evidence of benefit in managing cancer-related fatigue (Mock et al. 2003). Even at a moderate level, exercise training produces a more adaptive response by the cardio-respiratory system and greater exercise tolerance, as evidenced by increased cardiac output, lower heart rate and less fatigue, reflecting a reduced level of energy required to perform equivalent work (ACSM 2005).

Using the model to guide the intervention

In using the Levine Conservation Model to guide the development of the intervention, special care was taken to include all components of the model (Table 2). The exercise intervention tested in this study includes the Conservation of energy component within the Levine Model, in which the focus is on balancing the individual’s energy resources with energy expenditure. Conservation of energy is also addressed in informational materials provided to participants. These materials include a booklet on fatigue management that describes ways to conserve energy and make the most efficient use of the energy available. A booklet and video provide the specifics of the walking and strength training programme. Study materials also include daily logs that serve as a diary for many participants.

Table 2.

Components of the exercise intervention as aligned with the Levine Conservation Model

Conceptual framework concepts Conservation of energy Conservation of structural integrity Conservation of personal integrity Conservation of social integrity
Study variables Fatigue
Sleep		 Physical functioning Emotional distress
Quality of life		 Social functioning
Intervention components Fatigue booklet
Daily log
Walking booklet
Walking video		 Individualized walking programme
Daily log
Pedometer
Resistance bands		 Daily log
Bi-weekly phone calls
Pedometer		 Daily log
Bi-weekly phone calls
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Conservation of structural integrity is concerned with the process of maintaining or restoring the structure of the body. Structure and function are inter-related, and pathophysiological processes can change or threaten structural integrity. As the body adapts to energy depletion and fatigue by decreasing activities of daily living over a prolonged period of time, fatigue, muscle weakness and atrophy may result. Exercise can prevent or reverse the usual response to environmental challenges faced by patients with cancer. Conservation of structural integrity and physical functioning are addressed by the exercise programme itself. Not only are the logs and pedometers used as a means of measuring implementation of the intervention, but they also serve as an integral part of the intervention, providing both feedback and motivation. The exercise programme incorporates bi-weekly phone calls from a research nurse. These exchanges between nurse and participant include assessment of the participant’s tolerance of the exercise programme and negotiation of reasonable goals for exercise activity.

The Conservation of personal integrity emphasizes the concept of personal identity and sense of self. Illness threatens self-identity and sense of self, the foundations of personal integrity. The use of a home-based exercise programme in our study gives participants control of one aspect of their health promotion during an uncertain and difficult time in their lives, when many aspects seem out of the individual’s control. Also, the pedometer allows participants to track their own activity level, and daily logs can promote feelings of control and autonomy. Emotional state, quality of life and social functioning are emphasized in the bi-weekly phone calls, and the research nurses spend time discussing the walking programme and helping patients deal with the tsunami of feelings brought on by their diagnosis and treatment.

The Conservation of social integrity refers to living successfully in a social environment consisting of family, community and employment relationships. Cancer treatment presents major physiological and environmental challenges that affect social roles and quality of life, including reduced tolerance for levels of normal activity. Prior research has shown that early attempts to adapt to compromised energy levels include reductions in social activities (Mock et al. 2001). The reduction in energy and in tolerance for these social interactions has the potential to lead to isolation that may threaten emotional equilibrium. This resulting emotional disequilibrium is characterized by anxiety, depression and difficulty sleeping (Mock et al. 1997, Ancoli-Israel et al. 2001, Nail 2002, Ahlberg et al. 2003). Thus, improvement in, or maintenance of, energy levels resulting from the use of an exercise programme provides an opportunity to continue important social interactions.

It is worthwhile to note that some of the measurement tools used in this study have become elements of the intervention. For example, the daily logs completed by patients serve as an expressive narrative for some participants, as they record their progress, difficulties and frustrations along with personal reflections. They also become a means of tracking their adherence to the exercise programme. Early participants have reported that completing the logs and visualizing the pedometer readings have served as incentives for improving their exercise performance.

Discussion

During this project, the Levine Conservation Model proved to be a useful organizing framework for the study of a nurse-directed exercise intervention to manage fatigue in cancer patients. Levine indicates that the goal of the individual patient in the face of environmental challenges is adaptation: preserving an integrated self. As noted in the discussion of cancer and its impact on the individual, sustained environmental and psychological stress, as well as alternations in structural integrity, results in chronic fatigue behaviours. The model provides nursing implications for the international clinical care of cancer patients, i.e. the patient benefits from nursing interventions that promote and support adaptation to these challenges and maintain integrity of the individual. There is good evidence that nurse-directed exercise programmes facilitate adaptation by conserving energy and improving functional capacity (structural integrity) resulting in lower levels of fatigue in patients receiving cancer treatment (Galvao & Newton 2005, Schmitz et al. 2005, Mitchell et al. 2007). Exercise can also enhance personal integrity and social integrity, which are identified as conservation principles in the Levine Conservation Model.

Evidence for this is seen in earlier work guided by the model (Mock et al. 1998, 2001, 2005). Patients who exercised regularly during cancer treatment conserved energy as reflected in lower fatigue levels compared with patients who did not exercise regularly: the conservation of structural integrity was reflected in increased functional capacity in exercisers while there were decreased levels in non-exercisers. Conservation of personal integrity was demonstrated by lower mood distress scores and higher quality of life scores in exercisers. Finally, conservation of social integrity was indicated by increased scores on social functioning for regular exercisers while scores dropped for those with low levels of exercise (Mock et al. 2001). The walking exercise programme tested here was easily taught and monitored by oncology nurses within the context of cancer treatment in outpatient clinics. Advising patients about physical activity is becoming a routine component of nursing care in many countries (Douglas et al. 2006). The low-cost, low-risk intervention is internationally applicable as a health promoting component of cancer care.

In the study described here we were guided by the Levine Conservation Model in defining research variables, developing the intervention and determining the instruments and measurement periods to be used for data collection. Use of the model ensured that appropriate outcomes were used in the evaluation of the impact of the intervention; the focus was on the Levine Conservation Model concepts of enhancement of energy, structural integrity, personal integrity and social integrity. The model has also proved useful in the analysis and interpretation of data in our previous studies. We are using this framework in the current study to explain the study results in relation to the four conservation principles. The use of a conceptual model enables the researchers to test aspects of the underlying theory and to interpret findings within a scientific and theoretical context. The model is then further explicated for its value in guiding practice, e.g. identifying effective nursing interventions to mitigate fatigue and improve functioning during cancer therapies.

Limitations

The Levine Conservation Model is limited in guiding at least one important aspect of research; it is not specific enough to

What is already known about this topic

  • Nursing conceptual models can serve as facilitative frameworks for organizing and conducting research studies.

  • Theories describe proposed and testable relationships between variables that are conceptually linked.

  • There is a lack of clear examples of the use of conceptual models in the development and conduct of nursing research.

What this paper adds

  • The Levine Conservation Model is an illustration of a powerful organizing scheme for a randomized clinical trial testing the effects of exercise on cancer-related fatigue during chemotherapy or radiation therapy treatment.

  • Research methods in this clinical trial effectively test and support components of the Levine Conservation Model.

  • This heuristic model demonstrates the fundamental reciprocal relationships among nursing theory, nursing research and nursing practice.

explain the specific mediating mechanisms by which exercise training achieves physiological and psychosocial outcomes. Thus, additional biological theories (e.g., changes in functional capacity) and psychosocial theories (e.g., stress reduction or distraction) are needed to supplement the Levine Conservation Model for a full understanding of how exercise mitigates the fatigue experience. Another limitation is the lack of stated postulates to accompany the model. This provides an identified area for further development of the theory and has implications for further research with the model. Other recommended areas of cancer-related fatigue research using the model include the exploration of biological and psychosocial mediating mechanisms to further elucidate the relationships among components of the Levine Conservation Model.

Conclusion

The description of the model, and how it was employed to guide a nursing research project, should prove useful to other investigative teams as they seek to design their research and interpret study results within the context of nursing theory. Information gained from our ongoing research is adding to the body of literature suggesting that the Levine Conservation Model is a robust framework for designing and testing theory-based exercise interventions to mitigate cancer-related fatigue. Our experience, applicable on an international level, strongly supports the value of using a conceptual model as a framework for nursing research.

Contributor Information

Victoria Mock, Dept of Health Systems & Outcomes, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA, Director of Nursing Research Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland, USA.

Christine St. Ours, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA.

Sue Hall, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA.

Amy Bositis, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA.

Miriam Tillery, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA.

Anne Belcher, Johns Hopkins University School of Nursing, Baltimore, Maryland, USA.

Sharon Krumm, Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland, USA.

Ruth McCorkle, Center for Excellence in Chronic Illness Care, Yale University School of Nursing, New Haven, Connecticut, USA.

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