The benefits derived from cardiac rehabilitation are well established. Traditional rehabilitation programs use a combination of aerobic and resistance training, combined with lifestyle modification, to achieve desired goals. Although resistance training seems to be less effective than aerobic exercise in facilitating cardiovascular risk reduction, the additional benefits derived from an adjunctive resistance exercise program are no longer disputed. In 1990, the American College of Sports Medicine initially highlighted the importance of adding resistance training as part of a comprehensive exercise program (1). These recommendations were further enhanced in an update released in 1998 (2). After the release of these position stands, numerous organizations endorsed the inclusion of resistance training to exercise programs, including patients with stable coronary artery disease (3-5). Yet, despite the significant benefits observed with resistance training in various patient populations, the inclusion of resistance training into exercise-based programs for patients with chronic heart failure (CHF) remains controversial.
IMPACT OF CHF
Approximately 550,000 new cases of CHF are diagnosed per year, and more than 1 million hospitalizations are attributed to this condition annually (6). Patients with CHF generally have a poor clinical status and impaired exercise tolerance, which are due to both cardiac and skeletal muscle limitations. These symptoms are commonly attributed to reductions in peripheral blood flow and impaired perfusion, which lead to deficiencies in skeletal muscle function and further reduce exercise capacity (7-9). Ultimately, the inability to improve or maintain heart function at an appropriate level leads to a progression of the heart failure. Most current medical therapies used to treat CHF are aimed at modifying one or more of these abnormalities.
Historically, patients with CHF were advised to restrict physical exertion to activities of daily living; aerobic and resistance exercises were contraindicated because of concerns that the added stress would adversely affect an already compromised heart. In fact, early recommendations included a restriction on physical activity, reduced salt intake, and medication therapy (10). Although few large-scale trials evaluating the efficacy of exercise training on improved outcomes are available for patients with CHF, a number of studies have shown the beneficial effects of a medically prescribed and supervised exercise program in this patient population (10). Although CHF is associated with multiple system changes, including left ventricular dysfunction, impaired vasodilatory capacity, muscle fiberatrophy, decreased muscle fiber cross-sectional area, and dyspnea (11-13), it is thought that improvements in CHF stem from enhancements in muscle function and structure (14). Consequently, many, if not all, of the improvements in these various systems seem to be related to peripheral adaptations to the exercise training (10).
Numerous research studies have confirmed the safety of using aerobic exercise training in the rehabilitation of patients with CHF to improve exercise capacity (15-17), quality of life (16,17), and prognosis (15). The components of these exercise programs, however, are not well defined. Thus, current rehabilitative programs aimed at CHF focus primarily on improving cardiovascular and muscular endurance, muscular strength, and flexibility in an effort to enhance the ability to perform activities of daily living and improve functional independence. Exercise that involves large muscle groups, and is either continuous or intermittent in nature, seems to provide the most benefit to the patient. Exercise intensity is a critical component of the exercise program, with values ranging from 40% to 70% of V˙O2max being reported as safe and effective (10). The duration and frequency of the exercise program often are determined by the patient's physical condition and typically average 30 to 60 minutes per session, 3 to5 days per week (10). Initial exercise sessions should be in a medically supervised monitored setting, usually for a 3-month period, after which clinically stable patients may progress to an unmonitored exercise setting (18).
During the early years of cardiac rehabilitation, resistance training often was excluded because of concerns that it may induce myocardial ischemia, complex ventricular dysrhythmias, or hemodynamic abnormalities (19). Numerous research studies conducted in the 1980s, however, showed resistance training to be safe in stable cardiac patients (20). Benefits associated with resistance training include improvements in bone mineral density, body composition, muscular strength, insulin sensitivity, physical endurance, and basal metabolism (19). Weight training also has been shown to attenuate the rate-pressure product when any given load is lifted, which may reduce cardiac demands during activities like lifting or carrying packages. Although resistance training has become an increasingly used and recommended component in cardiac rehabilitation, the use of such training programs in patients with CHF remains controversial.
Although resistance training has been accepted as a means for improving muscular strength, power, and endurance in many patient populations, current guidelines do not fully embrace it for those with CHF (17). This lack of support presumably originated from early research, which raised concerns that increases in blood pressure and after load may accelerate the left ventricular remodeling process (21,22). Current research, however, indicates the potential for resistance training to assist in alleviating the symptoms and underlying structural deficiencies, without excessive hemodynamic burden (23) or further compromising left ventricular function (24). Specific benefits derived from resistance training in patients with CHF are shown in the Table. Thus, it seems reasonable that the application of specific resistance training programs is safe and induces favorable histochemical, metabolic, and functional adaptations in skeletal muscles, contributing to the treatment of muscle weakness and the unique myopathy associated with CHF (25).
Although randomized clinical trials are lacking, empirical evidence suggests that a comprehensive rehabilitative program is safe and beneficial for the CHF patient. Additionally, despite initial concerns, it seems that resistance training as a complementary therapy to aerobic training can provide independent and additive benefits. However, additional research, including large multicenter trials, are needed to determine appropriate training regimens and evaluate comprehensive outcomes, including mortality and cost benefits in this patient population (10).
1. American College of Sports Medicine Position Stand. The recommended quantity and quality of exercise for developing and maintaining cardiorespiratory and muscular fitness in healthy adults. Medicine & Science in Sports & Exercise ®
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6. Thom, T., N. Haase, W. Rosamond, et al. Heart Disease and Stroke Statistics-2006 Update: a report from the American Heart Association statistics committee and stroke statistics subcommittee. Circulation
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24. Levinger, I., R. Bronks, D. Cody, et al. The effect of resistance training on left ventricular function and structure of patients with chronic heart failure. International Journal of Cardiology
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