Physical inactivity and sedentary behaviour are significant risk factors for cardiovascular disease and all cause mortality. Meeting physical activity guidelines slows the progression of coronary artery disease improves risk factor profile for cardiac and other chronic diseases [#verdicchio-c-freene-n-hollings-m-et-al].   For people with coronary artery disease, mortality rates are 50% lower in those who are physically active compared to inactive counterparts.

Physical activity guidelines recommend that individuals participate in 150-300 minutes of moderate intensity activity; 75-150 minutes of vigorous aerobic physical activity, or a combined amount per week. Replacing sedentary time with any physical activity is associated with health benefits.

Supporting individuals to be more physically active, is an important component of all cardiac rehabilitation and heart failure management programs. 

Cardiac rehabilitation is a comprehensive, multidisciplinary intervention consisting of patient assessment, individual risk management, exercise prescription and support for behaviour change and psychosocial issues. Exercise-based cardiac rehabilitation programs are effective for reducing myocardial infarction and hospitalisation rates, and for improving exercise capacity, cardiac risk profiles and quality of life, sleep.  

Regular, sustained exercise improves cardiovascular health and slows the progression or partially reduces the severity of coronary atherosclerosis. The anti-atherosclerotic effect of exercise is in part brought about by improved endothelial function in response to increased vascular shear stress and by reduced chronic inflammation, which influences atherosclerotic pathogenesis and plaque stability.

Exercise improves cardiovascular risk factor profiles by:

• Lowering blood pressure
• Lowering low-density lipoprotein cholesterol (LDL-C) levels
• Increasing high-density lipoprotein cholesterol (HDL-C) levels
• Lowering serum triglycerides levels
• Reducing body weight and adiposity
• Improving insulin sensitivity
• Improving blood glucose homeostasis.

Patients with known disease or those who have had cardiac surgery should be referred to a specifically designed exercise program. Participation in habitual exercise not only improves physiological function, but can also enhance psychosocial outcomes.

There is strong evidence supporting the benefits of exercise training in people with heart failure (HF) and all patients should be referred to a specifically designed exercise program, if available.

Benefits of exercise training include improved quality of life, cardiorespiratory fitness and reduced symptoms of fatigue and dyspnoea. The gold standard measure of aerobic fitness, peak oxygen consumption (VO₂ peak), is strongly associated with survival in HF patients and typically increases by 15-20% over a training period of 8-12 weeks, with some studies showing increases of up to 30%.

These improvements in cardiovascular fitness are predominantly due to peripheral adaptations, such as improved oxidative capacity of skeletal muscle and enhanced peripheral blood flow following aerobic training, and muscle hypertrophy following resistance training.

Resistance training complements aerobic exercise, resulting in strength increases of up to 40%, depending on the characteristics of the training intervention.  In a systematic review and meta-analysis published in 2022, resistance training was found to elicit significant improvements in VO₂ peak and 6MWD, when compared to controls. [#fisher-s-smart-na-pearson-mj ]

Recent work has raised the possibility that high-intensity interval training may offer superior benefits to HF patients compared with low-to-moderate intensity continuous aerobic training with regard to VO₂ peak. However, results are not conclusive and should be interpreted with caution.

Psychological benefits of exercise training include reduced depression and anxiety, and improved quality of life. HF patients who exercise regularly also have better clinical outcomes.  The largest exercise training study in HF, the HF-ACTION trial, randomised 2,331 patients to aerobic exercise or usual care. After adjusting for predetermined prognostic factors, exercise training was associated with a 15% reduction in all-cause mortality and decreased the number of hospitalisations due to HF.

Is exercise safe for patients with heart failure?

Until recently,  research studies have been conducted predominantly in patients with stable symptoms (New York Heart Association [NYHA] Class I-III), HFrEF and young males, and in these cohorts, moderate-intensity exercise is well tolerated. In the many studies published to date, there have not been any reported deaths directly related to the effects of exercise training.

Far fewer studies have been published related to frail, older patients with heart failure, however available data suggests that these patients demonstrate high levels of adherence and report improvements in short performance physical battery, 6MWT, frailty scores and quality of life [#kitzman-dw-whellan-dj-duncan-p.-et-al].   Studies also suggest that those with more severe symptoms are most likely to demonstrate greater mortality and morbidity benefit from supervised exercise training compared to those with fewer symptoms and therefore should not be excluded from exercise training programs.

The hallmark of heart failure (HF) is exercise intolerance due to shortness of breath and fatigue. In people with HF, skeletal muscle function is often impaired and may contribute to symptoms that are experienced.

There are several reasons why skeletal muscle dysfunction or atrophy occurs:

1. Atrophy correlates with the magnitude of skeletal muscle apoptosis. Apoptosis in healthy people is the normal process of replacing old cells with new, but in HF apoptosis becomes dysfunctional and muscle cells are removed prematurely without adequate new cell replacements
2. As the number of muscle fibres is reduced so is the number of small blood vessels (capillaries) supplying these muscles. In HF, reduced capillarisation is compounded by increased levels of inflammation. The net result is impaired circulation to the already atrophied muscles, which precipitates premature muscle fatigue
3. Because of atrophy and impaired perfusion and hence oxygen delivery, highly reactive oxygen species are formed during even mild physical exertion. These worsen the already chronic inflammation. This process is known as 'oxidative stress'
4. Chronic inflammation and oxidative stress lead to biochemical abnormalities. One such example is elevated levels of noradrenaline which leads to an elevated heart rate (HR) and therefore increased cardiac work. This in turn adds to the vicious cycle of creating more oxidative stress, apoptosis, atrophy etc., as shown in the figure below

Figure: Development of skeletal muscle dysfunction

When prescribing exercise for patients with cardiac disease, it is important to consider the underlying physiology of the cardiac condition. For more detailed information, see exercise for specific clinical conditions.

Ischaemic heart disease

Individuals with ischaemic heart disease, but not HF, can be prescribed longer continuous exercise tasks unless they are limited by angina symptoms. Furthermore, the use of resistance training may be less detrimental to cardiac function in these patients. The presence of co-morbid diseases such as diabetes or chronic obstructive pulmonary disease (COPD), however, may require the exercise intensity and volume to be adjusted according to symptoms and not age expectations.

Heart failure

Exercise intolerance is a hallmark feature of HF with the primary limitation being impaired cardiac output (CO).   A CO of approximately 5 litres per minute is needed to sustain organ function and prevent symptoms of exertion. Healthy people can raise their CO to 15-20 litres per minute during physical stress, however patients with HF, may not be able to increase their CO to the same extent during exertion.

For patients with HF, there is often insufficient blood delivery to working muscles during exercise which is often compounded by a smaller skeletal muscle mass served by a deficient capillary bed. The net result is that the ability of someone with HF to extract oxygen from the blood is impaired. With consideration to the Fick equation, this means that CO is impaired in patients with HF, while the arterial-venous oxygen difference is also abnormally low.

The exercise guidelines for HFrEF and HFpEF are effectively the same, with both groups benefiting to a similar degree from aerobic exercise.  For older and frailer patients, as is commonly the case for those with HFpEF, resistance training may play a more significant role.  In these patients, resistance training aims to improve the active muscle mass available during physical exertion without the risk of compromising systolic function.

Functional class is also relevant when prescribing exercise, as patients with class III and IV symptoms may benefit from a lower intensity level, longer rest periods and slower progression rates to accommodate levels of fatigue and function.