The Impact of Fatigue on Exercise Performance

Transcription

1 The Impact of Fatigue on Exercise Performance Bash Belza The purpose of this paper is to discuss the impact of fatigue on exercise performance. First, fatigue will be defined and distinguished from similar constructs. Second, examples of instruments to measure fatigue in the rheumatic diseases are highlighted. Next, the social implications of fatigue are briefly mentioned. Fourth, methods in which fatigue impacts exercise performance are discussed. Fifth, the prevalence of fatigue in arthritis and its relationship to exercise will be presented. And last, areas of future research and roles of clinicians in managing fatigue relative to exercise performance are proposed. Fatigue is a fairly universal experience. Results from the National Health and Nutrition Examination Survey indicated that 14.3% of the male respondents and 20% of the female respondents reported experiencing fatigue [l]. For healthy individuals, fatigue results from identifiable events, such as strenuous physical exercise, a busy day at work, or emotional tension. Usually, rest or sleep brings relief. Both the fatigue and ensuing recovery period are normal experiences. Likewise, when otherwise normally healthy individuals are plagued with common viral illness, overwhelming fatigue is an often reported symptom. Regardless of the cause, the duration of fatigue in healthy individuals is usually time limited and treatable. To isolate a single cause of fatigue or suggest an effective remedy to ameliorate fatigue may not be so readily apparent for individuals with a chronic illness. A restful night of sleep may not completely relieve the Basia Belza, PhD. RN, is Assistant Professor in the Physiological Nursing Department, University of Washington, Seattle, Washington. Address correspondence to Basia Belza, PhD, RN, Physiological Nursing Department, SM-28, University of Washington, Seattle, WA Submitted for publication March 24,1994; accepted May 27, by the American College of Rheumatology. 176 fatigue, and the fatigue condition may not be transient. Furthermore, the presence of fatigue may have serious ramifications on activities of daily living and mental health. Living with a chronic illness, coping with its effects, and maintaining physical and psychological integrity all require energy. The ongoing management of a chronic condition requires one to learn and implement new self-care habits, monitor responses to therapy, and develop an awareness of cues to avert a crisis. Without energy there are limited resources for mobility, physical reserve, confidence to complete a task, and the means of responding to unexpected stress [2]. Of particular relevance to this paper is that a diminished level of energy impacts exercise performance. THE PHENOMENON OF FATIGUE Definition Fatigue is the enduring, subjective sensation of generalized tiredness or exhaustion. Enduring connotes that the sensation of fatigue has persisted over a period of time. Subjective implies that fatigue is a selfrecognized phenomenon imbedded in the individual s own evaluation of the current personal state. Generalized connotes that fatigue encompasses the person as a whole and is not restricted to specific anatomic structures, regions, or functions [3]. The fatigue that is described in this paper is more formally classified as central fatigue. In contradistinction, peripheral fatigue refers to an unusual exhaustion of muscles during exertion [4]. Fatigue is any point on a continuum in which the end points are the subjective state of feeling tired and the subjective state of exhaustion [5]. Multiple origins of fatigue may occur both within and between individuals. Fatigue is a complex phenomenon because psychological and physiological factors may be involved. The concept of fatigue is clearly evidenced in the sporting arena, in which, for /94/$5.00

2 Arthritis Care and Research Impact of Fatigue 177 example, at the end of a marathon, the loser may collapse while the winner, just as equally fatigued, has the capability to run an extra round in jubilation. Differentiating Fatigue from Similar Constructs Fatigue is a feeling, and as such, represents different things to different people [6]. Other terms used to describe fatigue include weariness, lack of energy, worn out, pooped, lethargic, lassitude, haggard, and bushed [6,7]. Often accompanying fatigue is the strong desire to rest, stop, or sleep. Several constructs may inappropriately be used synonymously with fatigue, such as weakness stiffness, or endurance. There is a voluntary component to fatigue that distinguishes it from weakness. An individual who is fatigued may be able to push him- or herself to perform necessary activities. In contrast, someone who is weak cannot voluntarily perform physical activities [8]. Whereas fatigue is the disinclination to activity or movement, stiffness is the actual discomfort experienced during movement of activity [9]. Whereas endurance is the ability to continue a particular task [lo], fatigue is the sensation that interferes with the ability to continue that same task. Measurement Recommendations for appraising fatigue differ based on the purpose of the assessment. Reasons for measuring fatigue include screening or classification, assessing individual status, distinguishing between groups, guiding management decisions, and evaluating the magnitude of change in response to treatment. Consistent with the definition of fatigue as a subjective sensation, the majority of instruments used in research and practice have employed a self-report format. Several instruments that have been developed and/or used to measure fatigue in rheumatic disease are presented here. The Multidimensional Assessment of Fatigue (MAF] scale is a 16-item scale that measures four dimensions of fatigue: severity, distress, impact, and timing [ll]. Fourteen items are numerical rating scales and two items have multiple choice responses. The instrument has shown evidence of strong reliability and validity in patients with rheumatoid arthritis (RA)[ll], healthy controls [12], fibromyalgia [13], and chronic fatigue syndrome (CFS) (Buchwald, personal communication). The Fatigue Scale is a 14-item instrument with physical and mental symptom subscales [14]. The scale has been tested in patients with CFS and patients attending a general medical clinic. It was shown to have good face validity, and it is sensitive to change. Rep- resentative items include: Do you have problems with tiredness? Are you lacking energy? Do you have difficulty sleeping? Respondents rate each question on a four-point Likert scale. The Profile of Mood States (POMS) measures a broad diverse set of six mood states: fatigue-inertia, vigoractivity, anger-hostility, confusion-bewilderment, tension-anxiety, and depression-dej ection [15]. The POMS has been tested in multiple clinical populations and healthy normal individuals and has shown strong reliability and validity. Respondents are asked to rate each of the 65 adjectives on a 0 (not at all] to 4 (extremely] scale based on how they have been feeling during the past week. The fatigue subscale consists of seven items: worn-out, listless, fatigued, exhausted, sluggish, weary, and bushed. The Profile of Fatigue-Related Symptoms (PFRS) is a 96-item multidimensional measure of fatigue incorporating the diverse symptoms associated with CFS [16]. The instrument was originally developed to assess patients in terms of severity of disease, to relate subjective symptoms to immunological and other findings, to evaluate the effects of treatment, and to compare symptomatology of CFS with other fatiguing illnesses. The instrument has four scales: emotional distress (e.g., sad, depressed), cognitive difficulty (e.g., slowness of thought, difficulty concentrating], fatigue (e.g., physically tired, limbs feel heavy], and somatic symptoms (e.g., back pain, cold hands or feet]. Respondents are asked to rate each of the 96 symptoms on a five-point Likert scale from 0 (not at all] to 4 (extremely]. When tested, these scales demonstrated good convergence with comparison measures and high reliability and internal consistency. The Fatigue Severity Scale (FSS) is a nine-item scale measuring symptoms associated with fatigue and impact. It was originally developed based on the characteristics of fatigue in multiple sclerosis (MS) and lupus [17]. It has fair internal consistency and stability over time and distinguishes patients with MS and lupus from controls. Respondents are asked to select a number on a seven-point Likert scale as to their agreement with each statement. Examples of statements include: my motivation is lower when I am fatigued; I am easily fatigued; and fatigue is among my three most disabling symptoms. Another method to measure fatigue is through single items. One question frequently used to evaluate outcomes in clinical trials for rheumatic diseases is to ask the patient how many hours elapse from the time of arising to the time of fatigue onset [MI. The rationale for this type of question is that the time of the onset of fatigue after arising is inversely proportional to the severity of the inflammatory process. Another type of

3 178 Belza Vol. 7, No. 4, December 1994 question used to assess fatigue is: Do you tire easily? [19]. Various other scales have been used to determine fatigue or energy levels: energy level on a 10-point scale from not-at-all to a lot [20]; fatigue intensity on a 4-point scale from none to severe [21]; or fatigue amount on a 4-point scale from not-at-all to a lot [22]. Although this approach requires minimal patient time and is simple to score, these measures have not typically been subject to stringent psychometric evaluation. Additionally, this type of questioning allows for the measurement of a single dimension of fatigue, such as severity, but fails to capture other dimensions such as intensity or timing. Social Implications Americans are oriented towards productivity. Value is frequently associated with the speed at which tasks are completed and the quantity at which one produces. This definition of success does not encourage the free expression of fatigue. In a society that rewards output, individuals complaining of fatigue may be perceived as lazy and as noncontributors. IMPACT OF FATIGUE ON EXERCISE PERFORMANCE Exercise is an activity in which the body performs work. Work implies that muscles contract and limbs usually move through space [lo]. One of the prerequisites to exercise is energy. Fatigue results when there is a lack of energy. Fatigue impacts exercise performance in a multitude of ways. Patients with chronic illnesses such as the rheumatic diseases may have frequent pain. The presence of pain is frequently associated with the presence of fatigue Ill]. When one is attempting to exercise and concurrently experiencing pain, the degree of fatigue severity may be higher. Fatigue may be associated with a shorter or less strenuous workout. There is less energy to expend so one shortens the length of time of the exercise or the degree of aerobic activity. Fatigue during exercise may lead to an increased risk for injury. One is less stable on hidher feet, has poorer coordination, or is less attentive to environmental hazards. There may be less enjoyment because there is an increased preoccupation with pushing oneself forward to meet preset exercise goals. There may be decreased motivation to plan for the next exercise session. The previous exercise session was so riddled with fatigue that there might be the tendency to cancel or break from the routine. When a significant reduction occurs in intensity, frequency, and/or duration of exercise, there is the potential for deconditioning to result. The result is greater physiologic stress and energy expenditure than would be expected. At intense levels of exercise, respiration and heart rate are limiting factors, and a person who is deconditioned will reach these limits at lower exertion levels. At moderate levels of exercise, a more rapid heart rate and respiration require more energy expenditure and produce earlier onset fatigue. In addition, heart rate and respiration are somatic markers that patients use to gauge exertion, recognize or anticipate fatigue, and regulate activity to avoid fatigue ~31. PREVALENCE OF FATIGUE AND ASSOCIATION WITH EXERCISE Next to pain, one of the common symptoms in rheumatic diseases is fatigue. Fatigue is frequently associated with inflammatory conditions; the two that will be mentioned here are RA and systemic lupus erythematosus (SLE). In RA, although most of the effects of the disease are located in the joints, its systemic nature produces extraarticular symptoms such as fatigue. Fatigue exists in all gradations of RA and typically increases during flares and decreases during remission [21]. In studies of fatigue in RA, fatigue has been found to be present in 88-93% of subjects [11,21]. Although the absence of fatigue is one of the criteria for clinical remission, the presence of fatigue is not a criterion for diagnosis [21]. Another rheumatic disease in which fatigue is prominent is SLE, an autoimmune disease primarily affecting young women. Constitutional symptoms such as fatigue are typically present during the onset of disease in 73% of patients and present anytime in the course of disease in 84% of patients [24]. Beginning evidence exists in studies of aerobic exercise in rheumatic disease that fatigue and exertion improve with moderate-intensity exercise. In a study of the effects of a stationary bicycle exercise program for women with RA, exercise subjects consistently reported improvement in fatigue, strength, and ability to do housework [25]. Other researchers have found that participants in an exercise and patient education program had significantly lower fatigue severity levels compared to controls [26]. In another study of patients with RA, subjects reported significantly less exertion required to exercise at light and medium workloads [27]. Less exertion at workloads that correspond to typical activities of daily living translates into more available energy and delayed onset of fatigue. Improvements in fatigue associated with SLE have also been

4 Arthritis Care and Research Impact of Fatigue 179 documented. After participating in an 8-week exercise program, subjects with SLE showed increased exercise endurance and aerobic capacity, and decreased submaximal exertion and fatigue [28]. Findings described here must be interpreted within the context of the study limitations. All the studies had small sample sizes. Additionally, Harkcom et al. [25] had no measure of fatigue conducted prior to the exercise intervention. The interventions implemented by Perlman et al. [26] included more than exercise, so the effects of exercise on fatigue cannot be separated from the problem solving taught to subjects. The significance of the results of the study by Robb-Nicholson et al. [28] were evidenced in the four-item visual analog scales but not supported by the POMS fatigue subscale. To the researcher cognizant of the weaknesses in these studies, the findings do demonstrate that fatigue can be modified through participation in exercise. RECOMMENDATIONS FOR FUTURE RESEARCH The gaps in our knowledge of the impact of fatigue on exercise performance serve as the basis for future research. How exercise improves fatigue has not been adequately researched. What is the mechanism by which exercise reduces fatigue? What role does improved muscle strength, cardiac stroke volume, mood, or sleep play? Is exercise more effective in reducing fatigue in certain rheumatic diseases than others? How does fatigue affect participation in a rehabilitation program? How much exercise is needed to ameliorate fatigue yet not contribute to overtraining? These questions represent several rich areas for research. IMPLICATIONS FOR CLINICIANS With the high prevalence of fatigue in rheumatic diseases, clinicians need to better assess and manage fatigue relative to exercise prescription and performance. Clinicians have the technical skills, frequency of contact, and credibility to work closely with patients who are fatigued. An awareness is needed that fatigue is a biopsychosocial phenomenon. To decrease the impact of fatigue on exercise performance, clinicians might consider the following strategies. At baseline, assess patients for the level of physical conditioning as evidenced by muscle weakness and atrophy, and cardiovascular tone. Determine whether fatigue-related problems are of physiological etiology, such as muscle weakness, or psychological etiology, such as depression, or a combination. Discuss motivation for exercising and factors that help with adherence. Assess fatigue on a regular basis using an instrument that is strong psychometrically and is multidimensional. Use results from a fatigue measure to help patients chart change in fatigue over time. Monitor associated symptoms such as inflammation and pain. Calculate the Training Index (TI] to determine the interrelationship of intensity and duration of exercise: intensity of effort (pulse during exercise/maximum heart rate] multiplied by the number of minutes of exercise (adapted from Hagberg [29]; Clark, personal communication]. Maximum heart rate is calculated by subtracting age from 220. Encourage balance between exercise (aerobic or nonaerobic) and rest (meditation, naps]. In summary, fatigue is a universal experience. For healthy individuals, fatigue results from identifiable events, is time limited, and is treatable with rest. For individuals with a chronic illness, determining the etiology and managing the fatigue is more complex. Fatigue does impact exercise performance in a multitude of ways. Through increased awareness and knowledge, clinicians can implement more effective strategies to reduce the adverse impact fatigue has on exercise performance. REFERENCES 1. Chen M: The epidemiology of self-perceived fatigue among adults. Prev Med 15:74-81, Miller J: Energy deficits in the chronically ill: the patient with arthritis. In Miller J (ed]: Coping with Chronic 111- ness: Overcoming Powerlessness. Philadelphia, FA Davis, Shaw D, Chesney M, Tullis F, Agersborg H: Management of fatigue: a physiological approach. Am J Med Sci 243: , Bennett R: Beyond fibromyalgia: ideas on etiology and treatment. J Rheumatol 19(Suppl): , Grandjean E: Fatigue. Am Ind Hyg Assoc J 31: , Atkinson, H: Women and Fatigue. New York, Pocket Books, Friedman H: Friedman H (ed): Problem Oriented Medical Diagnosis. Boston, Little, Brown, and Co, Gordon M: Differential diagnosis of weakness: a common geriatric symptom. Geriatrics 41:75-79, Polley H, Hunder G: Rheumatological Interviewing and Physical Examination of Joints, 2nd edition. Philadelphia, WB Saunders, Gerber L: Exercise and arthritis. Bull Rheum Dis 39:l- 9, Belza B, Henke C, Yelin E, Epstein W, Gilliss C: Dimensions and correlates of fatigue in rheumatoid arthritis. Nurs Res 33:93-99, 1993.

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