1 UC ProMotion, 2 Institute of Human Movement Sciences, University of Groningen and 3 Groningen Dialysis Center, Groningen University Hospital, The Netherlands
Correspondence and offprint requests to: Dr M. H. G. de Greef, Institute of Human Movement Sciences, University of Groningen, PO Box 196, 9700 AD Groningen, The Netherlands. E-mail: M.de.Greef{at}ppsw.rug.nl
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Abstract |
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Methods. Ninety-six haemodialysis patients of the Groningen Dialysis Center were randomized into an exercise group (n = 53) and a control group (n = 43). The exercise programme consists of cycling during dialysis together with a pre-dialysis strength training programme lasting 12 weeks. The intensity of the exercise programme is condition level 1216 according to the rate of perceived exertion (RPE). Motivational interviewing techniques were used for exercise counselling. Before and after the intervention, both groups were tested on behavioural change and physical fitness components such as reaction time, manual dexterity, lower extremity muscle strength and VO2 peak. Physiological conditions such as weight, blood pressure, haemoglobin and haematocrit values, cholesterol and Kt/V were obtained from the medical records. Health-related quality of life assessment included RAND-36 scores, symptoms and depression.
Results. A group x time analysis with MANOVA (repeated measures) demonstrates that participation in a low-to-moderate intensity exercise programme linked with exercise counselling yields a significant increase in behavioural change, reaction time, lower extremity muscle strength, Kt/V and three components of quality of life, and no significant effects in the control group.
Conclusion. Participating in a low-to-moderate intensity pre-conditioning exercise programme showed beneficial effects on behavioural change, physical fitness, physiological conditions and health-related quality of life.
Keywords: exercise; haemodialysis; health-related quality of life; physical fitness
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Introduction |
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There are no renal rehabilitation exercise programmes for haemodialysis patients in The Netherlands. To improve the physical condition of haemodialysis patients, the Groningen Dialysis Center has taken the initiative to develop a pre-conditioning programme for such patients. The graded and low-to-moderate intensity exercise programme aims to improve physical fitness, physiological condition and health-related quality of life with an endurance and strength training exercise programme. Exercise counselling is added to improve exercise adherence [10]. The purpose of the present study is to analyse and compare the effects of this pre-conditioning exercise programme, consisting of cycling, strength training and exercise counselling, on behavioural change, physical fitness, physiological condition and health-related quality of life in seden-tary haemodialysis patients.
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Subjects and methods |
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Patients
All haemodialysis patients (n = 128) at the Groningen Dialysis Center in The Netherlands were asked to participate in this study.
Exclusion criteria for exercise were severe cardiovascular disease, use of ß-blockers, unstable angina pectoris and orthopaedic complaints. The inclusion criterion are sedentary physical activity status (according to ACSM criteria). To assess the physical activity status, the self-reported Stage of Change Questionnaire was used [10]. Based on inclusion and exclusion criteria, 103 haemodialysis patients were randomized. Extra patients were randomized into the exercise group to compensate for the effects of drop-out. A flow diagram shows the progress of the patients through the phases of the trial (see Figure 1). Participation was voluntary, contingent on the approval of the patients supervising physician. Written informed consent was obtained from all patients who agreed to participate. Table 1 shows the demographic and clinical characteristics of patients recruited into the exercise and control groups. The exercise group consisted of 38 men and 22 women aged 2077 years (mean age 52), and the control group consisted of 30 men and 13 women aged 2283 years (mean age 58).
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Exercise counselling
The exercise counselling techniques used were based on the transtheoretical model, motivational interviewing and health counselling [12]. The central idea behind this is that behavioural change is a long-term process during which patients can be counselled, depending on their stage of change [10]. During the intervention, the exercise counsellors met with the haemodialysis patients four times. Conversation topics were the motivation of patients to enhance their physical activity and physical fitness, the stage of change, perceived barriers, exercise targets of haemodialysis patients and coping with exercise adherence. The exercise counsellor served as motivational support to stimulate patients to become and stay more active.
Data collection
Physical fitness
The physical fitness components assessed in the present study are exercise capacity, lower extremity muscle strength, manual dexterity and reaction time. Exercise capacity (VO2 peak) was assessed with the submaximal Åstrand cycling test [13]. This test predicts the maximal aerobic capacity from submaximal heart rates. The cycling test was held before the dialysis session, before and after the intervention, using a cycle ergometer (Corival, ProCare BV, The Netherlands) and a Polar S210TM to measure heart rate. Lower extremity muscle strength was assessed with the time to complete 10 repetitions of the sit-to-stand-to-sit test. [14]. The other two components were assessed with the Groningen Fitness Test for the Elderly (GFE). The GFE is reliable, validated and sensitive to changes in performance-based fitness of sedentary older adults (aged 5565 years) [15], and is used in this study because of the expected low performance-based fitness of haemodialysis patients.
Health-related quality of life
The Dutch version of the MOS Short-Form General Health Survey (RAND-36) was used to measure the patients generic health-related quality of life. This questionnaire was used because of its comprehensiveness, conciseness and high standards of reliability and validity [16]. Symptom frequency was measured using a scale based on the most common symptoms experienced by haemodialysis patients, such as tiredness, cramps, itching, shortness of breath, etc. [17]. The 20-item Self-rating Depression Scale (SDS) was used to assess depression. The SDS is reliable and valid for use as a screening instrument to identify depressive symptoms [18].
Physiological condition
Information about the physiological condition was assessed from patients medical status before and after the intervention, including weight, blood pressure, cholesterol levels, heart rate, haematocrit levels, haemoglobin levels and Kt/V.
Behavioural change
In this study, behavioural change was studied through self-efficacy, stage of change and perceived fitness. Self-efficacy was measured with the LIVAS questionnaire and brings out the capacity of one's physical competences [19]. According to the transtheoretical model, individuals pass through five common stages of change as they move toward the adoption of a regular exercise programme [10]. We measure the stage of change for each patient before and after the pre-conditioning exercise programme. For perceived fitness, patients were asked to give a grade between 1 and 10.
Statistical analysis
Data on physical fitness, health-related quality of life, physiological condition and behavioural change were analysed (SPSS Base 10.0) using MANOVA (repeated measures) to look for significant interaction (group x time) effects. Statistical significance was achieved at P<0.05. Effect sizes were calculated according to Cohen. Effect sizes (d scores) <0.20 indicated a low effect, between 0.50 and 0.80 a moderate effect, and >0.80 a large effect [20].
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Results |
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Physical fitness
Table 2 shows the physical fitness pre- and post-training results for the exercise and control groups. The MANOVA analysis shows a significant multivariate group x time interaction effect for reaction time [F(1,94) = 11.8, P = 0.002] and lower extremity muscle strength [F(1,94) = 3.92, P = 0.05]. No significant effects were shown within the control group. For the significant effects, large effect sizes were calculated for reaction time (d = 1.31) and lower extremity muscle strength (d = 1.48).
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Discussion |
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Except for the absence of effects on VO2 peak, the results of the exercise intervention on physical fitness and health-related quality of life in the exercise group are in agreement with those of other studies [2,5,6]. To our knowledge, the effects of an exercise programme on behavioural change and reaction time of haemodialysis patients has not been assessed before in other studies.
The physical fitness component of endurance was assessed with the submaximal Åstrand cycling test. In this study, the maximal aerobic capacity (VO2 peak) of 57 patients could be predicted, with 96 patients having taken the Åstrand cycling test. One important reason for this drop-out figure is muscular fatigue of haemodialysis patients. As a result, haemodialysis patients could not cycle at a constant workload for 6 min and therefore the VO2 peak could not be assessed. The fact that no effect on VO2 peak was found when assessing aerobic capacity may be due to the drop-out rate.
Furthermore, the duration of the low-to-moderate intensity exercise programme may be too short for a beneficial effect on all the haemodialysis patients who participated. Older participants in particular may take several weeks to adapt to the initial rigours of training and may therefore need a longer adjustment period to benefit optimally from an exercise programme.
Nevertheless, it appears from our study that, besides the known positive effects of exercise on physical fitness and health-related quality of life, there are additional benefits for those haemodialysis patients who exercise. The behavioural change that we found indicates that exercising patients developed a greater belief in their capacity to bring about a change of behaviour in themselves (self-efficacy). This helps to improve the self-image of these patients, who before the exercise programme often felt they were in decline.
The improved reaction time in the exercise group is an unexpected finding but will probably help patients in their activities of daily living. Together with the increased lower extremity muscle strength and the improved manual dexterity, patients in the exercise group could function better in everyday life, for example thanks to improvement in neuropsychological functions, maintaining agility, coordination, balance, decreasing chances of falling and less fear of movement as a result of better motor control.
The results of this study show that exercise increased Kt/V. This increase is interesting from a mechanistic point of view. Since the dialysis prescription had not changed, the exercise programme appears to be responsible for this improvement in dialysis efficiency. The most likely factor involved is cycling during dialysis. We speculate that improved muscle circulation leads to better wash-out of urea from this compartment, so that less urea rebound occurs directly after dialysis, which results in a higher equilibrated Kt/V value.
In summary, even short-term activity of low-to-moderate intensity improves a number of physiological and psychological parameters in haemodialysis patients. In view of the high cardiovascular mortality of this patient group, stimulation of physical activity should receive more emphasis in dialysis centres. A structured programme such as ours can help in this respect.
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Acknowledgments |
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Conflict of interest statement. None declared.
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References |
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