Article
Effects of Aerobic Exercise During Hemodialysis on Physical Functional Performance and Depression
Biological Research for Nursing 2015, Vol. 17(2) 214-221 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1099800414539548 brn.sagepub.com
Yueh-Min Liu, RN, MS1,2, Yu-Chu Chung, RN, PhD3, Jung-San Chang, MD, PhD4, and Mei-Ling Yeh, RN, PhD1
Abstract Previous studies have concluded that exercise training is beneficial to patients on hemodialysis (HD). Results, however, have shown that differences in the type, intensity, and frequency of physical exercise lead to variability in its effects on physical functional performance and depression. Further research is thus warranted. Our aim was to evaluate the effects of aerobic exercise on physical functional performance and depression during HD. Using a pretest–posttest control group design, we recruited HD patients and nonrandomly assigned them to an exercise group (n ¼ 13) that completed a 12-week aerobic exercise program during HD or a control group (n ¼ 11) that did no exercise during HD. The primary outcome measures were physical functional performance, as evaluated by the 6-min walk test and the sit-to-stand test, and depression, as evaluated by the Beck Depression Inventory II. The secondary outcome measures were albumin and triglyceride levels and hematocrit. Results revealed significant between-group differences in physical functional performance and depression but not in albumin level, hematocrit, or triglyceride level. Findings suggest that exercise may play a critical role in physical functional performance and may decrease depression. Exercise should be encouraged and performed during HD in HD centers. Keywords aerobic exercise, hemodialysis, physical function performance, depression, albumin, hematocrit, and triglyceride level
According to the U.S. Renal Data System (2012), the incidence of end-stage renal disease (ESRD) continues to increase each year. Taiwan has more than 60,125 patients with ESRD and the highest prevalence of ESRD in the world. Hemodialysis (HD) is the principal form of renal replacement therapy for ESRD, and approximately 91% of ESRD patients receive maintenance HD (Taiwan Society of Nephrology, 2013). HD is typically prescribed to be performed 3 times per week, 3–6 hr per session, for the rest of a patient’s life or until successful kidney transplant has been performed (Cheema & Singh, 2005). Muscle wasting, decreased visceral protein stores, and reduced physical functioning attributable to uremic myopathy and neuropathy have a significant impact on hospitalization and mortality rates among long-term HD patients (Kosmadakis et al., 2010). Muscle weakness and lack of energy are among the most common complaints of these patients (Storer, 2009). Causes of muscle weakness can include loss of muscle mass (atrophy) and reduced storage of protein in the body, which significantly affect mortality and hospitalization rates (Beddhu, Pappas, Ramkumar, & Samore, 2003). HD patients also have a high incidence of cardiovascular disease, and cardiovascular disease and related factors are the main cause of morbidity and mortality in these patients (Sarnak & Levey, 1999). Approximately two thirds of all patients with ESRD suffer from
dyslipidemia (Liu & Rosner, 2006), a common risk factor for cardiovascular disease (Junyent et al., 2010), and it is the cause of death in nearly 50% of HD patients (Al Wakeel et al., 2002). In one study, 84.5% of HD patients had abnormal levels of triglycerides, and 82–92% had lower than normal HDL cholesterol levels prior to the initiation of exercise therapy (Gordon, McGrowder, Pena, Cabrera, & Lawrence-Wright, 2012). Management of dyslipidemia would reduce the incidence of cardiovascular disease and mortality in HD patients. The most commonly observed psychological problem in HD patients is depression, with reported incidence ranging from
1
School of Nursing, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan, Republic of China 2 Hemodialysis Center, Cardinal Tien Hospital, New Taipei City, Taiwan, Republic of China 3 School of Nursing, Yuanpei University, Hsinchu City, Taiwan, Republic of China 4 Kaohsiung Medical University, Kaohsuing City, Taiwan, Republic of China Corresponding Author: Mei-Ling Yeh, RN, PhD, School of Nursing, National Taipei University of Nursing and Health Sciences, No. 365, Minte Road, Taipei, Taiwan, Republic of China. Email: [email protected]
Liu et al. 27.9% to 40.2% (Keskin & Engin, 2011; Ugurlu, Bastug, Cevirme, & Uysal, 2012). Depression is, however, underrecognized and undertreated in this patient population, which markedly increases the mortality rate (Hedayati et al., 2008). Hospitalization and mortality rates within the first year of HD for patients with depression were more than twice than those of patients without depression. In a previous study, researchers found a significant positive correlation between depression and death in patients receiving chronic HD therapy (Troidle et al., 2003). A sedentary lifestyle is common in HD patients because their physical capabilities and levels of physical fitness and function are markedly reduced due to chronic renal failure. More than half of HD patients are considered mildly disabled based on tests of physical functional performance (Jhu, Kuo, & Tseng, 2011). Inactivity in HD patients has been associated with increased obesity and mortality (Kosmadakis et al., 2010). Exercise programs among HD patients have shown promise both for reducing depression and increasing physical functional performance (Eriksson & Gard, 2011). Dialysis exercise programs have resulted in a significant increase in aerobic capacity and peak oxygen uptake and reduced cardiovascular risk (Heiwe & Jacobson, 2011) and depression (Ouzouni, Kouidi, Sioulis, Grekas, & Deligiannis, 2009). In one previous study, investigators found that a brief period of exercise could affect aerobic capacity in patients receiving maintenance HD; however, aerobic capacity had little relationship to physical symptoms or depression after a 1-month follow-up (Carmack et al., 1995). The authors concluded that insufficient training duration and the limited number of interventions might account for the lack of effect on physical and psychological variables. In contrast, several studies have revealed a relationship between the two types of variables. A 10-month intradialytic exercise training program (60–90 min per session) improved functional capacity and depression in HD patients (Ouzouni et al., 2009). A 24-week intradialytic resistance training program (25 min per session) resulted in improved physical function, physical performance, and exercise capacity among HD patients (Segura-Ortí, Kouidi, & Lisón, 2009). A 12-week aerobic exercise training program during HD not only increased physical function but also contributed to controlling blood pressure and anemia (Reboredo et al., 2010). An 8-week aerobic exercise and resistance training program during HD affected serum creatinine level but not weight or hemoglobin level (Afshar, Sheggarfy, Shavandi, & Sanavi, 2010). A 12-month run-in control period with a 6-month exercise program for HD patients demonstrated that physical exercise could safely increase physical performance but had no effect on laboratory variables, including hemoglobin, albumin, triglycerides, cholesterol, calcium, and phosphate (Bulckaen et al., 2011). A 2-month aerobic exercise program (15 min per day, 3 times a week) significantly improved serum phosphate and potassium levels, but not serum calcium and hemoglobin levels, among HD patients (Makhlough, llali, Mohseni, & Shahmohammadi, 2012). Finally, seven of the eight studies examined in a systematic review revealed positive effects of exercise on depression, but the authors concluded that more
215 highly controlled studies on the effect of physical exercise on depression, focusing on the type, intensity, and frequency of exercise are still needed (Eriksson & Gard, 2011). The wide variation in type, intensity, and frequency of exercise explored in these previous studies led to differences in the findings on the effects of exercise on biochemical indicators and depression. Further study to determine the most effective exercise program for these patients is, therefore, warranted. In this study, we aimed to evaluate the effects of an aerobic exercise program on physical functional performance and depression in patients undergoing HD.
Method Research Design and Sample We used a quasi-experimental pretest and posttest, control group design (Figure 1). ESRD outpatients were recruited from an HD center in an 872-bed northern regional hospital in Taiwan. Inclusion criteria were being greater than 20 years of age, having received maintenance HD for more than 6 months, undergoing dialysis treatment 3 times per week, and having arteriovenous grafts or native fistulas in the upper extremity. Exclusion criteria were severe muscle weakness or skeletal deformity, malignant arrhythmia, unstable angina, hospitalization during the study, and uncontrolled blood pressure. Participants were nonrandomly assigned to one of the two groups based on the days they came for HD. Patients who came for HD on Mondays, Wednesdays, and Fridays were assigned to the experimental group and received the 12-week aerobic exercise program. Patients who came for HD on Tuesdays, Thursdays, and Saturdays were assigned to the control group and received routine dialysis care only.
Aerobic Exercise Program Participants completed the 30-min aerobic exercise sessions during the first 2 hr of each dialysis session, 3 times per week for 12 weeks, using a horizontal electromagnetic cycle ergometer (Medical Exercise Peddler 3000, Medi-Bike, Taiwan). Each exercise session consisted of three phases: warm up, conditioning, and cool down. Before the start of each exercise session, we placed a blood pressure cuff and heart rate and SpO2 monitors on participants and left them on throughout the session. HD physicians also assessed the participant's clinical condition at this time (i.e., shortness of breath, cardiovascular symptoms, blood pressure, and heart rate). Once the session began, the research assistant measured the participant’s blood pressure, heart rate (Criticare, Systems Inc., Waukesha, WI) and SpO2 (Dash 2000, GE Healthcare, Wisconsin, U.S.A.) electronically every 5–10 min for safety. Participants were excluded from the exercise session if their systolic blood pressure was higher than 180 mmHg, diastolic blood pressure was higher than 95 mmHg, heartbeat was below 60 beats/min, or SpO2 was less than 88%. The warm-up phase consisted of 5 min of stretching of the lower limbs and low-load aerobic exercise at an intensity of 8–9 of 20 on the Borg Rate of Perceived Exertion (RPE) scale.
216
Biological Research for Nursing 17(2)
Assessed for eligibility (N = 25)
Enrolled (N = 24) Written and verbal informed consent Pretest: demographic and clinical characteristics, 6-minute walk distance, sit-to-stand movements, biochemical data, and depression
Dialysis on Mondays, Wednesdays, Fridays Exercise group (n = 13) Stationary cycle, 30 min/session, 3 sessions/week for 12 weeks
Attrition (n = 3): hypotension (n = 1), lower-limb weakness (n = 1), and fatigue (n = 1)
Exercise group (n = 10)
Dialysis on Tuesdays, Thursdays, Saturdays Control group (n = 11) Usual care
Attrition (n = 1): knee pain (n = 1)
Control group (n = 10)
Posttest: 6-minute walk distance, sit-to-stand movements, biochemical data, and depression Figure 1. Study design and participant flowchart.
The conditioning phase included 20 min of aerobic exercise. Intensity was prescribed on the basis of perceived exertion, exercise heart rate, and blood pressure. The exercise participants were requested to exercise at an RPE between 11 (fairly light) and 13 (somewhat hard; Borg, 1970), and intensity was monitored every 5 min. Participants were encouraged to increase the rate of rotation if the Borg scale value was less than 11 and decrease the rate of rotation if the value was greater than 13. During the cooldown period, participants performed light exercise with no load at an intensity of 8–9 on the RPE scale. The criteria considered for interrupting the aerobic exercise session included intense physical exhaustion, chest pain, dyspnea, dizziness, significant changes in heart rate or blood pressure, or fatigue of the lower limbs. Participants were included in the analyses if they completed at least 10 of the 12 sessions out of any consecutive 4-week period during the 12-week aerobic exercise program.
Outcome Measures Demographic and clinical characteristics. We collected age, gender, marital status, education level, symptoms of HD, and reasons for not exercising from participants. From the medical record, we collected cause of kidney failure and HD duration. Physical functional performance. The 6-min walk test (6MWT) is frequently used to measure physical function in HD patients (Reboredo et al., 2010). In this study, participants performed the 6MWT along a 20-m long and 2-m wide walkway in a quiet hospital corridor. We placed markers every 5 m along the length of the corridor. Participants were instructed to walk as far as they could in 6 min. They were allowed to stop and rest if needed but were instructed to resume walking when they felt able to do so. Reasons for immediately stopping a 6MWT included chest pain, dyspnea, leg cramp, or pale appearance.
Liu et al. In HD patients, the 6MWT value has been reported to be highly positively correlated with VO2 peak during the cardiopulmonary test (Reboredo et al., 2007). We used the sit-to-stand test (STS-60) as an indirect measure of lower limb muscle strength and endurance (McIntyre et al., 2006). The STS-60 test measures the number of times a participant can get up from a chair and sit down again during a 60-s period. The STS-60 is a feasible way to measure changes in physical function resulting from exercise (Segura-Ortí et al., 2009). Depression. We used a Chinese version of the Beck Depression Inventory II (C-BDI-II; Beck, Steer, & Brown, 1996/2000) to measure severity of depression. The C-BDI-II is a 21-item self-administered instrument. Respondents rate each item on a 4-point scale ranging from 0 to 3. The severity of depression is determined by summing the ratings: Total score ranges from 0 to 63, with scores of 0–13 indicating minimal depression, 14–19 indicating mild depression, 20–28 indicating moderate depression, and 29–63 indicating severe or major depression (Lu, Che, Chang, & Shen, 2002). Cronbach’s α, a measure of internal consistency reliability, was .91 for the BDI-II (Beck, Steer, Ball, & Ranieri, 1996) and .93 in this study. Biochemical data. Albumin level (normal > 4.0 g/dl), hematocrit (male: 36–50%; female: 34–47%), and triglyceride level (normal < 200 mg/dl) were measured before the start of and after the completion of the entire aerobic exercise program. We obtained 1 cc of blood for the hematocrit test and 3–4 cc for the biochemical test as patients underwent HD therapy. Blood samples were processed immediately and analyzed by using an XE-5000 automated hematology analyzer (Sysmex UK and SIEMENS) at the central laboratory of the study hospital (B17D0B043).
Procedure The institutional review board of the study granted hospital approval for the conduct of this study (CTH-100-3-5-44). We obtained written informed consent from all participants after they received a full explanation of the study. Participants were allowed to withdraw themselves from the study at any time without affecting their care. All data collected remained confidential throughout the study and were used in the analyses. The nurse researcher (SL) on the research team administered the aerobic exercise program to all participants after receiving training on the protocol by another member (YM) of the research team. All participants started their individual exercise programs at the beginning of the month. The nurse researcher collected the outcome measures before the start of and after the end of the 12-week exercise program. Measures were completed at the HD clinic before the start of HD treatment.
217 Table 1. Demographic and Clinical Characteristics of Hemodialysis Patients Who Completed the Study, by Study Group.
Variable Age (years); mean (SD) Gender, male; n (%) Marital status, n (%) Single Married Education level completed, n (%) High school and below College and above Cause of kidney failure, n (%) Diabetes Other (hypertension, kidney disease, and gout) Hemodialysis duration, months; mean (SD) Symptoms of hemodialysis (n) Hypotension (Yes/no) Hypertension (Yes/no) Itching (Yes/no) Muscle weakness (Yes/no) Cramping (Yes/no) Reason given for not exercising (n) Fatigue Others (hemodialysis, lacking the will, and weather)
Control group
Exercise group
n ¼ 10
n ¼ 10
p
33.2 (7.0) 44.3 (6.7) .002a 6 (60) 5 (50) 1.00b 1.00b 2 (20) 3 (30) 8 (80) 7 (70) 1.00b 7 (70) 8 (80) 3 (30) 2 (20) .37b 7 (70) 4 (40) 3 (30) 6 (60) 61.7 (55.6)
87.5 (74.7)
.68a
4/6 1/9 0/10 1/9 2/8
6/4 0/10 2/8 5/5 5/5
.65b 1.00b .47b .14b .35b .07b
9 1
5 5
a
Mann–Whitney U test. Fisher’s exact test.
b
Mann–Whitney U test were used to verify homogeneity between groups. The between-group differences in the effects of exercise were analyzed using paired and independent t-tests.
Results Demographic and Clinical Characteristics Of the 25 patients who were eligible to participate, 24 signed the informed consent form and were included in the study. Of these, four dropped out for the following reasons: knee pain (n = 1), hypotension (n = 1), lower limb weakness (n = 1), and fatigue (n = 1). In all, 20 participants (83.33% of the initial number; 9 female and 11 male; mean age, 38.8 ± 8.8 years [range 21–52 years]) completed the study, with 10 adhering to and completing the aerobic exercise program and 10 completing the study in the control group. Table 1 presents participants’ demographic and clinical characteristics. All characteristics (p > .05) except age (p = .002, exercise group significantly older) were similar between groups.
Data Analysis IBM SPSS 20.0 for Windows was used to analyze data. Demographic data and medical history data were analyzed using descriptive statistics. The χ2 test, Fisher’s exact test, and
Physical Functional Performance As shown in Table 2, there were no between-group differences in the pretest 6MWT (t = −1.98, p = .06) or STS-60 (t = −0.47,
218
Biological Research for Nursing 17(2)
Table 2. Outcome Assessment at Baseline and After 12 Weeks of Exercise Training.
Outcome assessment 6-min walk distance (m) Control group Experimental group t valueb (p) Sit-to-Stand repetitions Control group Experimental group t Valueb (p) Depression (score)c Control group Experimental group t Valueb (p)
Pretest
Posttest
Pre–post change
Mean (SD)
Mean (SD)
Mean (SD)
t Valuea (p)
230.4 (84.9) 295.8 (61.4) 1.98 (.06)
218.9 (82.1) 342.6 (52.5) 4.01 (.001)
11.5 (6.4) 46.8 (43.4) 4.20 (.002)
5.69 (
Effects of Aerobic Exercise During Hemodialysis on Physical Functional Performance and Depression
Biological Research for Nursing 2015, Vol. 17(2) 214-221 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/1099800414539548 brn.sagepub.com
Yueh-Min Liu, RN, MS1,2, Yu-Chu Chung, RN, PhD3, Jung-San Chang, MD, PhD4, and Mei-Ling Yeh, RN, PhD1
Abstract Previous studies have concluded that exercise training is beneficial to patients on hemodialysis (HD). Results, however, have shown that differences in the type, intensity, and frequency of physical exercise lead to variability in its effects on physical functional performance and depression. Further research is thus warranted. Our aim was to evaluate the effects of aerobic exercise on physical functional performance and depression during HD. Using a pretest–posttest control group design, we recruited HD patients and nonrandomly assigned them to an exercise group (n ¼ 13) that completed a 12-week aerobic exercise program during HD or a control group (n ¼ 11) that did no exercise during HD. The primary outcome measures were physical functional performance, as evaluated by the 6-min walk test and the sit-to-stand test, and depression, as evaluated by the Beck Depression Inventory II. The secondary outcome measures were albumin and triglyceride levels and hematocrit. Results revealed significant between-group differences in physical functional performance and depression but not in albumin level, hematocrit, or triglyceride level. Findings suggest that exercise may play a critical role in physical functional performance and may decrease depression. Exercise should be encouraged and performed during HD in HD centers. Keywords aerobic exercise, hemodialysis, physical function performance, depression, albumin, hematocrit, and triglyceride level
According to the U.S. Renal Data System (2012), the incidence of end-stage renal disease (ESRD) continues to increase each year. Taiwan has more than 60,125 patients with ESRD and the highest prevalence of ESRD in the world. Hemodialysis (HD) is the principal form of renal replacement therapy for ESRD, and approximately 91% of ESRD patients receive maintenance HD (Taiwan Society of Nephrology, 2013). HD is typically prescribed to be performed 3 times per week, 3–6 hr per session, for the rest of a patient’s life or until successful kidney transplant has been performed (Cheema & Singh, 2005). Muscle wasting, decreased visceral protein stores, and reduced physical functioning attributable to uremic myopathy and neuropathy have a significant impact on hospitalization and mortality rates among long-term HD patients (Kosmadakis et al., 2010). Muscle weakness and lack of energy are among the most common complaints of these patients (Storer, 2009). Causes of muscle weakness can include loss of muscle mass (atrophy) and reduced storage of protein in the body, which significantly affect mortality and hospitalization rates (Beddhu, Pappas, Ramkumar, & Samore, 2003). HD patients also have a high incidence of cardiovascular disease, and cardiovascular disease and related factors are the main cause of morbidity and mortality in these patients (Sarnak & Levey, 1999). Approximately two thirds of all patients with ESRD suffer from
dyslipidemia (Liu & Rosner, 2006), a common risk factor for cardiovascular disease (Junyent et al., 2010), and it is the cause of death in nearly 50% of HD patients (Al Wakeel et al., 2002). In one study, 84.5% of HD patients had abnormal levels of triglycerides, and 82–92% had lower than normal HDL cholesterol levels prior to the initiation of exercise therapy (Gordon, McGrowder, Pena, Cabrera, & Lawrence-Wright, 2012). Management of dyslipidemia would reduce the incidence of cardiovascular disease and mortality in HD patients. The most commonly observed psychological problem in HD patients is depression, with reported incidence ranging from
1
School of Nursing, National Taipei University of Nursing and Health Sciences, Taipei, Taiwan, Republic of China 2 Hemodialysis Center, Cardinal Tien Hospital, New Taipei City, Taiwan, Republic of China 3 School of Nursing, Yuanpei University, Hsinchu City, Taiwan, Republic of China 4 Kaohsiung Medical University, Kaohsuing City, Taiwan, Republic of China Corresponding Author: Mei-Ling Yeh, RN, PhD, School of Nursing, National Taipei University of Nursing and Health Sciences, No. 365, Minte Road, Taipei, Taiwan, Republic of China. Email: [email protected]
Liu et al. 27.9% to 40.2% (Keskin & Engin, 2011; Ugurlu, Bastug, Cevirme, & Uysal, 2012). Depression is, however, underrecognized and undertreated in this patient population, which markedly increases the mortality rate (Hedayati et al., 2008). Hospitalization and mortality rates within the first year of HD for patients with depression were more than twice than those of patients without depression. In a previous study, researchers found a significant positive correlation between depression and death in patients receiving chronic HD therapy (Troidle et al., 2003). A sedentary lifestyle is common in HD patients because their physical capabilities and levels of physical fitness and function are markedly reduced due to chronic renal failure. More than half of HD patients are considered mildly disabled based on tests of physical functional performance (Jhu, Kuo, & Tseng, 2011). Inactivity in HD patients has been associated with increased obesity and mortality (Kosmadakis et al., 2010). Exercise programs among HD patients have shown promise both for reducing depression and increasing physical functional performance (Eriksson & Gard, 2011). Dialysis exercise programs have resulted in a significant increase in aerobic capacity and peak oxygen uptake and reduced cardiovascular risk (Heiwe & Jacobson, 2011) and depression (Ouzouni, Kouidi, Sioulis, Grekas, & Deligiannis, 2009). In one previous study, investigators found that a brief period of exercise could affect aerobic capacity in patients receiving maintenance HD; however, aerobic capacity had little relationship to physical symptoms or depression after a 1-month follow-up (Carmack et al., 1995). The authors concluded that insufficient training duration and the limited number of interventions might account for the lack of effect on physical and psychological variables. In contrast, several studies have revealed a relationship between the two types of variables. A 10-month intradialytic exercise training program (60–90 min per session) improved functional capacity and depression in HD patients (Ouzouni et al., 2009). A 24-week intradialytic resistance training program (25 min per session) resulted in improved physical function, physical performance, and exercise capacity among HD patients (Segura-Ortí, Kouidi, & Lisón, 2009). A 12-week aerobic exercise training program during HD not only increased physical function but also contributed to controlling blood pressure and anemia (Reboredo et al., 2010). An 8-week aerobic exercise and resistance training program during HD affected serum creatinine level but not weight or hemoglobin level (Afshar, Sheggarfy, Shavandi, & Sanavi, 2010). A 12-month run-in control period with a 6-month exercise program for HD patients demonstrated that physical exercise could safely increase physical performance but had no effect on laboratory variables, including hemoglobin, albumin, triglycerides, cholesterol, calcium, and phosphate (Bulckaen et al., 2011). A 2-month aerobic exercise program (15 min per day, 3 times a week) significantly improved serum phosphate and potassium levels, but not serum calcium and hemoglobin levels, among HD patients (Makhlough, llali, Mohseni, & Shahmohammadi, 2012). Finally, seven of the eight studies examined in a systematic review revealed positive effects of exercise on depression, but the authors concluded that more
215 highly controlled studies on the effect of physical exercise on depression, focusing on the type, intensity, and frequency of exercise are still needed (Eriksson & Gard, 2011). The wide variation in type, intensity, and frequency of exercise explored in these previous studies led to differences in the findings on the effects of exercise on biochemical indicators and depression. Further study to determine the most effective exercise program for these patients is, therefore, warranted. In this study, we aimed to evaluate the effects of an aerobic exercise program on physical functional performance and depression in patients undergoing HD.
Method Research Design and Sample We used a quasi-experimental pretest and posttest, control group design (Figure 1). ESRD outpatients were recruited from an HD center in an 872-bed northern regional hospital in Taiwan. Inclusion criteria were being greater than 20 years of age, having received maintenance HD for more than 6 months, undergoing dialysis treatment 3 times per week, and having arteriovenous grafts or native fistulas in the upper extremity. Exclusion criteria were severe muscle weakness or skeletal deformity, malignant arrhythmia, unstable angina, hospitalization during the study, and uncontrolled blood pressure. Participants were nonrandomly assigned to one of the two groups based on the days they came for HD. Patients who came for HD on Mondays, Wednesdays, and Fridays were assigned to the experimental group and received the 12-week aerobic exercise program. Patients who came for HD on Tuesdays, Thursdays, and Saturdays were assigned to the control group and received routine dialysis care only.
Aerobic Exercise Program Participants completed the 30-min aerobic exercise sessions during the first 2 hr of each dialysis session, 3 times per week for 12 weeks, using a horizontal electromagnetic cycle ergometer (Medical Exercise Peddler 3000, Medi-Bike, Taiwan). Each exercise session consisted of three phases: warm up, conditioning, and cool down. Before the start of each exercise session, we placed a blood pressure cuff and heart rate and SpO2 monitors on participants and left them on throughout the session. HD physicians also assessed the participant's clinical condition at this time (i.e., shortness of breath, cardiovascular symptoms, blood pressure, and heart rate). Once the session began, the research assistant measured the participant’s blood pressure, heart rate (Criticare, Systems Inc., Waukesha, WI) and SpO2 (Dash 2000, GE Healthcare, Wisconsin, U.S.A.) electronically every 5–10 min for safety. Participants were excluded from the exercise session if their systolic blood pressure was higher than 180 mmHg, diastolic blood pressure was higher than 95 mmHg, heartbeat was below 60 beats/min, or SpO2 was less than 88%. The warm-up phase consisted of 5 min of stretching of the lower limbs and low-load aerobic exercise at an intensity of 8–9 of 20 on the Borg Rate of Perceived Exertion (RPE) scale.
216
Biological Research for Nursing 17(2)
Assessed for eligibility (N = 25)
Enrolled (N = 24) Written and verbal informed consent Pretest: demographic and clinical characteristics, 6-minute walk distance, sit-to-stand movements, biochemical data, and depression
Dialysis on Mondays, Wednesdays, Fridays Exercise group (n = 13) Stationary cycle, 30 min/session, 3 sessions/week for 12 weeks
Attrition (n = 3): hypotension (n = 1), lower-limb weakness (n = 1), and fatigue (n = 1)
Exercise group (n = 10)
Dialysis on Tuesdays, Thursdays, Saturdays Control group (n = 11) Usual care
Attrition (n = 1): knee pain (n = 1)
Control group (n = 10)
Posttest: 6-minute walk distance, sit-to-stand movements, biochemical data, and depression Figure 1. Study design and participant flowchart.
The conditioning phase included 20 min of aerobic exercise. Intensity was prescribed on the basis of perceived exertion, exercise heart rate, and blood pressure. The exercise participants were requested to exercise at an RPE between 11 (fairly light) and 13 (somewhat hard; Borg, 1970), and intensity was monitored every 5 min. Participants were encouraged to increase the rate of rotation if the Borg scale value was less than 11 and decrease the rate of rotation if the value was greater than 13. During the cooldown period, participants performed light exercise with no load at an intensity of 8–9 on the RPE scale. The criteria considered for interrupting the aerobic exercise session included intense physical exhaustion, chest pain, dyspnea, dizziness, significant changes in heart rate or blood pressure, or fatigue of the lower limbs. Participants were included in the analyses if they completed at least 10 of the 12 sessions out of any consecutive 4-week period during the 12-week aerobic exercise program.
Outcome Measures Demographic and clinical characteristics. We collected age, gender, marital status, education level, symptoms of HD, and reasons for not exercising from participants. From the medical record, we collected cause of kidney failure and HD duration. Physical functional performance. The 6-min walk test (6MWT) is frequently used to measure physical function in HD patients (Reboredo et al., 2010). In this study, participants performed the 6MWT along a 20-m long and 2-m wide walkway in a quiet hospital corridor. We placed markers every 5 m along the length of the corridor. Participants were instructed to walk as far as they could in 6 min. They were allowed to stop and rest if needed but were instructed to resume walking when they felt able to do so. Reasons for immediately stopping a 6MWT included chest pain, dyspnea, leg cramp, or pale appearance.
Liu et al. In HD patients, the 6MWT value has been reported to be highly positively correlated with VO2 peak during the cardiopulmonary test (Reboredo et al., 2007). We used the sit-to-stand test (STS-60) as an indirect measure of lower limb muscle strength and endurance (McIntyre et al., 2006). The STS-60 test measures the number of times a participant can get up from a chair and sit down again during a 60-s period. The STS-60 is a feasible way to measure changes in physical function resulting from exercise (Segura-Ortí et al., 2009). Depression. We used a Chinese version of the Beck Depression Inventory II (C-BDI-II; Beck, Steer, & Brown, 1996/2000) to measure severity of depression. The C-BDI-II is a 21-item self-administered instrument. Respondents rate each item on a 4-point scale ranging from 0 to 3. The severity of depression is determined by summing the ratings: Total score ranges from 0 to 63, with scores of 0–13 indicating minimal depression, 14–19 indicating mild depression, 20–28 indicating moderate depression, and 29–63 indicating severe or major depression (Lu, Che, Chang, & Shen, 2002). Cronbach’s α, a measure of internal consistency reliability, was .91 for the BDI-II (Beck, Steer, Ball, & Ranieri, 1996) and .93 in this study. Biochemical data. Albumin level (normal > 4.0 g/dl), hematocrit (male: 36–50%; female: 34–47%), and triglyceride level (normal < 200 mg/dl) were measured before the start of and after the completion of the entire aerobic exercise program. We obtained 1 cc of blood for the hematocrit test and 3–4 cc for the biochemical test as patients underwent HD therapy. Blood samples were processed immediately and analyzed by using an XE-5000 automated hematology analyzer (Sysmex UK and SIEMENS) at the central laboratory of the study hospital (B17D0B043).
Procedure The institutional review board of the study granted hospital approval for the conduct of this study (CTH-100-3-5-44). We obtained written informed consent from all participants after they received a full explanation of the study. Participants were allowed to withdraw themselves from the study at any time without affecting their care. All data collected remained confidential throughout the study and were used in the analyses. The nurse researcher (SL) on the research team administered the aerobic exercise program to all participants after receiving training on the protocol by another member (YM) of the research team. All participants started their individual exercise programs at the beginning of the month. The nurse researcher collected the outcome measures before the start of and after the end of the 12-week exercise program. Measures were completed at the HD clinic before the start of HD treatment.
217 Table 1. Demographic and Clinical Characteristics of Hemodialysis Patients Who Completed the Study, by Study Group.
Variable Age (years); mean (SD) Gender, male; n (%) Marital status, n (%) Single Married Education level completed, n (%) High school and below College and above Cause of kidney failure, n (%) Diabetes Other (hypertension, kidney disease, and gout) Hemodialysis duration, months; mean (SD) Symptoms of hemodialysis (n) Hypotension (Yes/no) Hypertension (Yes/no) Itching (Yes/no) Muscle weakness (Yes/no) Cramping (Yes/no) Reason given for not exercising (n) Fatigue Others (hemodialysis, lacking the will, and weather)
Control group
Exercise group
n ¼ 10
n ¼ 10
p
33.2 (7.0) 44.3 (6.7) .002a 6 (60) 5 (50) 1.00b 1.00b 2 (20) 3 (30) 8 (80) 7 (70) 1.00b 7 (70) 8 (80) 3 (30) 2 (20) .37b 7 (70) 4 (40) 3 (30) 6 (60) 61.7 (55.6)
87.5 (74.7)
.68a
4/6 1/9 0/10 1/9 2/8
6/4 0/10 2/8 5/5 5/5
.65b 1.00b .47b .14b .35b .07b
9 1
5 5
a
Mann–Whitney U test. Fisher’s exact test.
b
Mann–Whitney U test were used to verify homogeneity between groups. The between-group differences in the effects of exercise were analyzed using paired and independent t-tests.
Results Demographic and Clinical Characteristics Of the 25 patients who were eligible to participate, 24 signed the informed consent form and were included in the study. Of these, four dropped out for the following reasons: knee pain (n = 1), hypotension (n = 1), lower limb weakness (n = 1), and fatigue (n = 1). In all, 20 participants (83.33% of the initial number; 9 female and 11 male; mean age, 38.8 ± 8.8 years [range 21–52 years]) completed the study, with 10 adhering to and completing the aerobic exercise program and 10 completing the study in the control group. Table 1 presents participants’ demographic and clinical characteristics. All characteristics (p > .05) except age (p = .002, exercise group significantly older) were similar between groups.
Data Analysis IBM SPSS 20.0 for Windows was used to analyze data. Demographic data and medical history data were analyzed using descriptive statistics. The χ2 test, Fisher’s exact test, and
Physical Functional Performance As shown in Table 2, there were no between-group differences in the pretest 6MWT (t = −1.98, p = .06) or STS-60 (t = −0.47,
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Table 2. Outcome Assessment at Baseline and After 12 Weeks of Exercise Training.
Outcome assessment 6-min walk distance (m) Control group Experimental group t valueb (p) Sit-to-Stand repetitions Control group Experimental group t Valueb (p) Depression (score)c Control group Experimental group t Valueb (p)
Pretest
Posttest
Pre–post change
Mean (SD)
Mean (SD)
Mean (SD)
t Valuea (p)
230.4 (84.9) 295.8 (61.4) 1.98 (.06)
218.9 (82.1) 342.6 (52.5) 4.01 (.001)
11.5 (6.4) 46.8 (43.4) 4.20 (.002)
5.69 (
