Physical activity and long-term prognosis in patients with stable coronary artery disease: How often, how intense, and how long?

The terms ‘physical activity’, ‘exercise’ and ‘physical fitness’ are often confused and sometimes used interchangeably. In 1985, Caspersen et al. clearly defined the terms as follows. Physical activity was defined as ‘any bodily movement produced by skeletal muscles that results in energy expenditure’. It can be measured in kilocalories. The amount of caloric expenditure is calculated by the total amount of bodily movements and the intensity, duration and frequency of muscular contractions. Physical activity can also be categorized as occupational, conditioning, household, sports or other activities in daily life. Although the amount of energy expenditure during sleep is small, sleep is also categorized as physical activity. ‘Exercise’ is commonly used interchangeably with ‘physical activity’; however, it is ‘a subset of physical activity that is planned, structured, and repetitive and has as a final or an intermediate objective the improvement or maintenance of physical fitness’. Exercise is one of the important parts of physical activities because of the relatively high energy expenditure. In addition, sports and conditioning are able to improve and maintain physical fitness levels. Physical fitness is ‘a set of attributes that are either healthor skill-related’. There are five health-related components of physical fitness, as follows: cardiorespiratory endurance, muscular endurance, muscular strength, body composition, and flexibility. Each component can be measured and ranges from low to high using specific tests (Figure 1). Physical inactivity has been identified as an important risk factor for the development of coronary artery disease (CAD). In contrast, regular exercise and physical activity, including any leisure interests that involve increased energy expenditure, are associated with lower mortality in patients with stable CAD. The European Society of Cardiology guideline recommends moderate-to-vigorous-intensity aerobic exercise training 3 times a week and for 30min per session in patients with stable CAD. In addition, sedentary patients with CAD are strongly encouraged to start light-intensity exercise programs after adequate exercise-related risk stratification. Numerous studies have suggested various beneficial effects of regular physical activity on coronary risk factors, circulating blood, heart and vasculature in patients with CAD. Exercise training ameliorates body composition, blood pressure, plasma lipid profiles, insulin sensitivity, glucose intolerance, platelet activation, number of progenitor cells, endothelial dysfunction, atherosclerotic development, collateral formation, resting heart rate, myocardial perfusion, pathological remodeling of left ventricle, wall compliance, contraction–relaxation velocity and cardiac output. We have previously reported an association between the percent changes in coronary plaque volume assessed using intravascular volumetric ultrasonography and physical activity in patients who participated in phase II cardiac rehabilitation after acute coronary syndrome (ACS). The percent change in the plaque volume was significantly and negatively correlated with daily physical activity evaluated using a pedometer. We have also reported the association between the changes in coronary plaque components assessed using serial integrated backscatter intravascular ultrasonography and physical activity in patients who participated in phase II cardiac rehabilitation after ACS. Percent change in the lipid volume was significantly