Hansen, Dominique MSc; Berger, Jan BSc; Dendale, Paul MD, PhD; De Rybel, Rudy MD; Meeusen, Romain PhD
Rehabilitation and Health Centre, Virga Jesse Hospital, Hasselt (Messrs Hansen and Berger and Dr Dendale), Department of Human Physiology and Sportsmedicine, Vrije Universiteit Brussel, Brussels (Mr Hansen and Dr Meeusen), and Department of Cardiology, Algemeen Stedelijk Ziekenhuis, Aalst (Dr De Rybel), Belgium.
Corresponding Author: Romain Meeusen, PhD, Vrije Universiteit Brussel, Faculty LK, Department of Human Physiology and Sportsmedicine, Pleinlaan 2, 1050 Brussels, Belgium, (email@example.com).
PURPOSE: The aim of this study was to analyze the effect of the prolongation of exercise sessions (from 40 to 60 minutes) on training adherence in the rehabilitation of patients with coronary artery disease (CAD).
METHODS: In this prospective, randomized clinical trial, 417 CAD patients (mean age = 63 ± 10 years, 78% males) followed a 7-week exercise training intervention, 3 sessions each week, at 65% of the maximal oxygen uptake capacity. Subjects were randomly assigned to 40-minute (n = 198) or 60-minute (n = 219) exercise sessions, with equal time distribution on the different exercise modalities (42%—treadmill, 33%—bike, and 25%—arm cranking device, in each session). During the exercise training intervention, dropout, as well as the reasons for dropout, was registered.
RESULTS: At 7 weeks of exercise training, dropout rate was comparable between groups (∼19.9%, P > .05). However, patients with acute myocardial infarction and/or coronary artery bypass graft surgery were more likely to complete the exercise training intervention (P < .05).
CONCLUSION: The prolongation of the exercise sessions does not interfere with the training adherence in the early rehabilitation of CAD patients.
Cardiac rehabilitation is a cornerstone in the treatment of coronary artery disease (CAD), because these programs significantly reduce cardiovascular mortality and morbidity during follow-up1; therefore, recommendations for the amount of exercise in cardiac rehabilitation have been formulated.2 However, the impact of the amount of exercise on training adherence remains to be investigated in CAD patients. Preventing dropout is essential for an exercise intervention program to suppress atherosclerotic lesion progression in these patients.3 Evidence indicates that higher training intensities will lower training adherence whereas higher training frequencies have no impact.4–6 Even though we recently reported no differences in the clinical effectiveness between 40-minute and 60-minute exercise sessions in the early rehabilitation of CAD patients,7 there still might be a valid impetus for the prolongation of the exercise sessions in certain individuals or patient groups. Therefore, it is important to establish the impact of this training modality on exercise adherence in cardiac rehabilitation. This inquiry emerges since it has been shown that the lack of time represents an important barrier to the maintenance of exercise in healthy individuals.8,9 In this study, we investigated the effects of the duration of the exercise sessions on training adherence during the rehabilitation of CAD patients. It was hypothesized that the prolongation of the exercise sessions would lower training adherence because of a lack of time.
Patients with CAD (40% with acute myocardial infarction and 60% with stable CAD) were referred to our coronary revascularization unit. Patients were revascularized by percutaneous coronary intervention (63%), coronary artery bypass graft surgery (CABG, 29%), or received medical treatment (8%). Patients were excluded in the presence of pulmonary and renal comorbidity, peripheral artery disease, orthopedic limitations, rheumatic disease, or presenting myocardial ischemia and/or severe ventricular arrhythmias during baseline exercise testing (to obtain a homogeneous population of low-risk CAD patients). All participating subjects signed an informed consent. The hospital ethical committee approved this study.
Patients were randomly assigned into 2 subgroups (40-minute vs 60-minute session groups) and followed an aerobic exercise training intervention. Percutaneous coronary intervention and CABG patients were entered into this exercise training intervention within 1 and 3 weeks, respectively, after revascularization. At baseline, body anthropometrics were assessed and general patient characteristics were collected. During the exercise training intervention, training adherence was evaluated.
Body mass was measured to the nearest 0.1 kg by using a calibrated analogue weight scale (Tanita model TBF-300, Tanita Corp, Tokyo, Japan) and height was measured to the nearest 0.1 cm. Body mass index was calculated from the ratio of weight (kg) to height (m2).
Training adherence was evaluated at the end of the sixth week of exercise training (≥18 exercise sessions). Those patients who did not complete 7 weeks of exercise training because of nonmedical or medical reasons, or exercised on average less than 2 exercise sessions each week, were considered as dropout patients. Medical reasons were defined as cardiovascular events, orthopedic injuries, and/or hospitalization or surgical intervention for any indication. When musculoskeletal discomfort or pain appeared throughout the intervention, the type of exercise was changed so that these exercises could be executed without symptoms. However, exercise intensity, frequency, and duration of the exercise sessions remained constant. From those patients who did not complete the exercise training intervention, the reason for dropout was determined by telephone within 14 days of nonattendance.
Aerobic Exercise Intervention
The exercise training intervention included only endurance training.2 No strength training exercises were performed. All subjects exercised under close supervision 3 days per week for a total duration of 7 weeks. Exercise training intensity was determined by baseline peak oxygen uptake (VO2peak) assessment. Subjects exercised at a heart rate corresponding to 65% of baseline VO2peak. One subgroup exercised for 60 minutes each exercise training session, and the other subgroup for 40 minutes each exercise training session. In both groups, exercise time for each training session was apportioned as follows, 42% on the treadmill, 33% on the cycle ergometer, and 25% on the arm cranking device. The training intensity was guided by heart rate monitoring (Polar, Oy, Finland). The target heart rate was kept constant during the exercise training intervention. When β-blocker treatment was changed, a new target heart rate was formulated by retesting the workload–heart rate relationship during cycling after 4 days of altered β-blocker therapy.
All data were expressed as means ± SD and analyzed by SPSS software program for Microsoft Windows, version 13.0. At baseline, groups were compared by 1-way analysis of variance or by a χ2 test. Dropout rates were compared between groups by χ2 tests. Binary multivariate logistic regression analysis was executed for analyzing the relationship between dropout and all baseline parameters simultaneously. A 2-tailed probability level of P < .05 was considered to be significant.
CAD patients (N = 417) were included in the exercise training intervention and randomly assigned to 40-minute (n = 198) or 60-minute (n = 219) exercise sessions. At baseline, general features, cardiac pathology/ intervention, and the living distance to the rehabilitation center were not different between subgroups (P > .05; Table 1).
Eighty-three patients (19.9%) did not complete the exercise training intervention (Figure 1 and Table 2). The following reasons for dropout were reported: 39.7%—lack of motivation, 18.2%—cardiovascular events, 15.7%—return to work, 14.4%—transport difficulties, 4.8%—exercise training was continued at home or for undefined reasons, 1.2%—the intervention was found to be too heavy or because of negative advice from the physician. Between subgroups, the reasons for dropout were not significantly different (P > .05).
At 7 weeks of exercise training, despite different durations of exercise sessions between subgroups, dropout rate for nonmedical reasons was not different between groups (40-minute [16.6%] vs 60-minute [16.0%], P > .05). Dropout for medical reasons was also not different between groups (40-minute [3.0%] vs 60-minute [4.1%], P >.05; Table 2).
The type of revascularization (OR=4.7; 95% CI = 1.6–14.4; P < .01) was significantly associated with dropout rate because of nonmedical reasons; that is, CABG patients adhered significantly more to the exercise training intervention (91.4%) than percutaneous coronary intervention patients (80.7%). Experiencing an acute myocardial infarction was also associated with dropout rate (OR = 2.1; 95% CI = −1.1 to −3.8; P < .05); that is, acute myocardial infarction patients adhered significantly more to the exercise training intervention (86.8%) than chronic CAD patients (81.0%).
Exercise adherence is of the utmost importance in the treatment of CAD. As long-term training adherence is essential to slow the progression of atherosclerotic lesions, preventing dropout is essential for cardiac rehabilitation to be successful.3 In the preset study, training adherence was found to be similar between 40-minute and 60-minute exercise sessions (∼80%) in the first few weeks of cardiac rehabilitation. Therefore, the hypothesis that the prolongation of the exercise sessions would lower training adherence because of a lack of time was not supported. Of all of the exercise training modalities, it appears that only exercise intensity affects training adherence in sedentary individuals.4–6 Lower adherence with higher exercise intensities is believed to be related to a higher injury rate.4 In addition, it might be difficult for previously sedentary individuals to exercise with great subjective effort during each exercise session.4–6 Fortunately, this study suggests that the duration of the exercise sessions should not be a factor that alters exercise motivation in the first few weeks of cardiac rehabilitation.
Our findings are important for the practice of cardiac rehabilitation. We have recently shown that increasing individual session duration did not induce greater changes of the body anthropometrics, exercise performance capacity, blood lipid profile, and resting hemodynamics in the early rehabilitation of revascularized CAD patients.7 Therefore, increased session duration did not seem to be of great clinical impact. However, there still may be value for such an approach in certain individuals or patient groups, for example, obese or hypertensive patients. In this regard, it is important to determine the effect of such session prolongation on the exercise adherence. In previous studies investigating healthy subjects, it has been suggested that limited time to engage in exercise represents an important cause of dropout from exercise training interventions; nonetheless, we were unable to reproduce such findings in our population of CAD patients. Therefore, we suggest that such exercise session prolongation in cardiac rehabilitation does not interfere with the training adherence.
The occurrence of orthopedic injuries is also an important reason for dropout from exercise training.10 In our study, we carefully followed patients throughout the exercise intervention for the occurrence of musculoskeletal symptoms. In case of musculoskeletal discomfort or pain, the exercise modalities were modified so that these symptoms were no longer present throughout the intervention. However, exercise intensity, frequency, and duration of the sessions remained constant. In addition, patients with a history of orthopedic injuries and/or rheumatoid disease had been excluded from the study initially. Therefore, our results should be interpreted on the assumption that exercises were modified according to patient musculoskeletal complaints and are applicable only to patients without a history of orthopedic injuries and/or rheumatoid disease.
Patients admitted to the hospital with an acute myocardial infarction and/or CABG patients were more likely to complete the training intervention. Previous studies have reported similar findings.11–13 It might be presumed that patients who had undergone surgery or suffered an acute coronary event are more convinced of the need to participate in exercise training interventions.
This study is limited by its relatively short follow-up period. It remains to be determined whether training adherence is affected by the duration of the exercise sessions in cardiac rehabilitation during a follow-up more than 7 weeks. In conclusion, the prolongation of exercise sessions does not affect training adherence in early rehabilitation of CAD patients.
This work was supported by an unrestricted research grant from Hartcentrum Hasselt vzw.
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