Introduction Exercise training

Introduction
Exercise training (ET) is suggested to improve aerobic capacity, prognosis, health-related quality of life (QOL) in patients with heart failure(HF). The purpose of this study is to determine the effect of exercise on Exercise Capacity in HF. The following four studies discuss the effectiveness of exercise training on functional status, all-cause mortality, hospital admission rate and health-related QOL of patients with HF.

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A study by Corvera-Tindel et al (2004) discussed the effects of a 12 weeks, low-intensity (40%-65%)home walking exercise program(HWE) on functional status (exercise capacity and functional performance)and symptoms (dyspnea and fatigue) in HF patient. All patients (n=79)were randomized into the training group (n =42) underwent HWE training, and the “usual activity” control group (n = 37). Time and distance walked were recorded by a pedometer given to patient. Both walking distances measured by the 6-minute walk test and post global rating of symptoms were improved, when compared with a no-exercise control. The limitation of this study included that research assistants conducted the 6-MWT were not blinded to the subgroups. They should be blinded to treatment allocation to minimise possible bias in assessing outcome measures. There were also minor clinical events such as flu, effects of comorbidities interrupted the 51.4% patients in the training program. The compliance rates progressively declined from 81% in the 5th week to 65% to 71% in the last 6 weeks. Low compliance rate may have influenced the training effects on peak Vo2.

With strengthening exercises prescribed in conjunction, Dracup et al (2007) aim to evaluate the effects of a home-based exercise program which consisted aerobic and resistance exercises on clinical outcomes in HF. The primary hypothesis was a low-level, home-based exercise program would improve clinical outcomes in patients with HF. The Secondary hypotheses focused on QOL, functional performance, and the psychological states of anxiety, depression, and hostility. A total of 173 patients were randomized with systolic HF to control(n=87)or home-based exercise (n=86). The current study demonstrated no improvement in all-cause mortality from participation in home-based exercise. However, the exercise program resulted in reduced number of multiple (2 or more) hospitalizations compared with the control group: 12.8% versus 26.6%, respectively (P = .018). The limitation was patients randomized to the experimental group have low compliance to exercise as only 44% of them had complete pedometer and daily diary data. Underdosage of exercise intensity and duration may have result in insignificant change in exercising group. A physiological benefit is unlikely if patients in exercise group do not perform the correct dose of exercise. It is a legitimate concern that patients in this study may not have achieved an adequate amount of exercise.

In a larger cohort, O’Connor et al (2009) conducted a Controlled Trial Investigating Outcomes of Exercise Training (HF-ACTION) to measure the effectiveness and safety of exercise training in medically optimized, stable systolic CHF patients (left ventricular ejection fraction LVEF ?35%). A total of 2331 patients were randomized from 82 centers from various countries to the usual care plus aerobic exercise training group or a group with usual care alone. The intervention consisting of 36 supervised, moderate-intensity training (60% to 70% heart rate reserve),followed by home-based training, with median follow-up of 30 months. The HF-ACTION authors reported no evidence of significant difference in the intervention effects as measured on either the primary outcome (all-cause mortality or hospitalisation) or key secondary clinical end point of health-related quality of life across a number of patient-defined subgroups. After adjustment for highly prognostic predictors of mortality (duration of exercise test, LVEF, Beck Depression Inventory II score, and history of atrial fibrillation), exercise training was linked with modest significant reductions for both clinical end points . The median improvement in peak VO2 in the exercise training group was only 4%. This less-than-expected training effect reflected a low adherence rate to exercise in the training group, as only 30% of subjects attained the targeted min/week. One of the limitation in this study was cross over effect. A significant percentage of patients (55%) in the usual care alone group were dissatisfied. Although patients
were not told to follow an exercise regimen during this period, 8% of control patients exercised regularly. Thereby diminishing the study’s ability to detect a significant effect of ET on the primary outcome.

Finally, a study by Belardinelli et al ( 2012) aim to investigate the effects of a 10-year supervised moderate ET program on sustained improvement in functional capacity and QOL in New York Heart Association (NYHA) class II and III CHF patients. A study of 123 patients were randomized into a supervised trained group (T group, n =63) and a nontrained group (NT group, n= 60). The T group underwent a supervised ET at 60% of peak oxygen consumption (VO2), 2 times weekly for 10 years.In general, sustained improvement in functional capacity were reported by those patients who undergo a 10-year supervised ET program of moderate intensity. Hospital readmission ( p < 0.001) and cardiac mortality (p < 0.001) than was lower in the T group and QOL score (p < 0.05), was significantly better in the T group versus the NT group. Hence, the clinical benefits of exercise training in systolic CHF can be expected to be long lasting. Supervision seems to be an important factor to decrease dropouts and increase adherence to long-term exercise scheme. Overall, the drop-out rate was low and participation in training was adequate due to supervision. However, potential of bias may exist as for NT group, they were free to do aerobic activities such as walking and swimming.

Discussion
Based on the four articles, exercises were beneficial on improving heart capacity. The study by Corvera-Tindel et al (2004) showed that in patients with HF, a progressive home walking exercise program for 12 weeks is acceptable. It help to increase walking distance, and decreases global rating of symptoms. However the focused was upon the immediate physical effects of the exercise protocols rather than examining any long-term physical benefits, in terms of morbidity and mortality. A reduction in hospital re-admission rates, improved morbidity, and a decline in mortality are the key indicators of the benefits of therapies for patients with HF. As such, they are the important outcome measures for assessing the effects of exercise training on patients with heart failure. Other three articles did address these outcome measures.

All four studies have been conducted in the era of contemporary medical therapy for HF. In HF-ACTION trial, 94% of patients were receiving ?-blockers and angiotensin-receptor blocker or ACE inhibitors, and 45% had an implantable cardioverter defibrillator or implanted biventricular pacemaker. Similarly, medications were distributed in the 2 groups of patients in 10 year exercise training as angiotensin- converting enzyme inhibitors or angiotensin receptor blockers were given in 100% of patients .Given the proven survival advantage of these medical treatments, it might be expected that any incremental all-cause mortality benefit with exercise is likely to be small.

No survival advantage with exercise training seen in Dracup et al are in accordance with HF-ACTION trial but not with that of Belardinelli et al, which focused on 10 year supervised exercise training and concluded that ET compared with usual care did improve the health-related QOL of patients with HF. One major concern is the reporting of compliance to exercise interventions. While the reports included the intended prescription exercise dose, it is impossible to determine adherence and fidelity. Without basic reporting of these parameters, the exercise dose received cannot be quantified. This may have a significant bearing on intervention efficacy and the results. There are several important differences between these 3 studies. The 10 year exercise training was supervised and the adherence rate was excellent (88%). Supervision leads to good compliance and ensures exercise intensity and duration at the levels prescribed. The ability for patients to adopt an exercise programme on their own was ideally with support from community-based health professionals. A cost-effective, safe, long- term, supervised maintenance model has yet to be developed. A home program would eliminate the time and ‘ease of access’ constraints to participation, although it would introduce problems of supervision for safety and adherence purposes.

Conclusion
In conclusion, the four articles showed that exercises for patients with HF is safe . Improvements in exercise capacity, hospitalization and health-related QOL with exercise training can be obtained, despite variation in training intensity, the type of supervision of training and outcome measures. The exercises may also reduce mortality in the longer term. Future clinical research of exercise-based interventions in HF need to consider the interventions to enhance the long-term maintenance of exercise training that can be delivered in a home-based setting.