INTRODUCTION — A sedentary lifestyle has been recognized as an independent risk factor for premature development of coronary heart disease (CHD) [1]. The public has become well aware of this relationship and many have embarked on voluntary exercise programs based upon the assumption that exercise will lead to effective prevention of atherosclerotic cardiovascular disease (ASCVD) [2]. Regular physical exercise is often recommended as a means of primary and secondary ASCVD prevention [3,4].
The role of both exercise and fitness in the primary and secondary prevention of atherosclerotic CVD will be reviewed here. An overview of the benefits and risks associated with exercise is presented separately. (See "The benefits and risks of aerobic exercise".)
LIMITATIONS OF THE EVIDENCE — The evidence from prospective, randomized clinical trials to establish the benefit of exercise is limited. There are several reasons for this limitation:
●Successful, randomized clinical trials require good adherence in order to show a difference between the groups at the end of the study. In the case of exercise, it is not possible from an ethical or practical standpoint to prevent those assigned to the control group from engaging in exercise (drop-ins).
●Long-term adherence in the group assigned to exercise is often diminished by noncompliance (drop-outs). After several years, the level of exercise might be similar in both groups, thereby preventing any evaluation of the value of exercise.
●The randomized trials that have been carried out have generally had small numbers of patients and have been inconclusive with regard to the benefits of exercise on clinically meaningful endpoints [5].
Much of the evidence for the benefit of exercise comes from long-term observational studies showing that those who exercise regularly have significantly less coronary heart disease (CHD) and a reduced risk of primary cardiac arrest [6]. When compared with the least active individuals, the most active individuals had a 30 to 40 percent lower risk of developing CHD or cardiovascular disease (CVD) [7,8]. This inverse association between amount of exercise and risk of CHD or CVD appears to be present regardless of age, sex, race, or ethnicity although comparative data are limited [7].
Unfortunately, observational data is subject to bias, since the decision to exercise is only one of the many choices made in adopting a healthy life style. As examples, a heart healthy diet, abstinence from cigarette smoking, and regular medical care may contribute to the improved health of those who also get regular exercise. Thus, attribution of exercise as a prevention of CHD is confounded by other favorable reductions in risk characteristics.
POTENTIAL BENEFICIAL EFFECT ON RISK FACTORS — Improvements in cardiovascular and general physical fitness and an overall enhancement in the quality of life are ample reasons to embrace physical exercise [9]. In addition, exercise has beneficial effects on weight control and several other important cardiovascular risk factors (table 1) [10,11]. (See "The benefits and risks of aerobic exercise".)
●Improvement in lipid profile – Exercise reduces serum triglycerides and increases serum high-density lipoprotein (HDL) cholesterol, with variable effects on total cholesterol, low-density lipoprotein (LDL) cholesterol, and very low-density lipoprotein (VLDL) cholesterol. (See "Effects of exercise on lipoproteins and hemostatic factors".)
●Reduction in blood pressure – The institution of a regular exercise regimen (such as jogging two miles or riding a bicycle for 45 minutes) can, within four weeks, lower the BP by as much as 5 to 15 mmHg in patients with primary hypertension (formerly called "essential" hypertension). (See "Exercise in the treatment and prevention of hypertension".)
●Treatment and possible prevention of type 2 diabetes mellitus – Exercise training programs increase activity of mitochondrial enzymes, leading to improved muscle energetics, decreased insulin resistance, and a lower rate of progression to overt type 2 diabetes. In addition, exercise (eg, brisk walking) also has a cardiovascular benefit similar to that seen for secondary prevention in nondiabetics. (See "Exercise guidance in adults with diabetes mellitus" and "Prevention of type 2 diabetes mellitus", section on 'Exercise'.)
●Reduction in inflammation – There is increasing evidence that inflammation, as manifested in part by elevations in serum C-reactive protein, plays an important role in atherosclerosis. Regular exercise reduces the atherogenic activity of blood mononuclear cells, with a decrease in the production of atherogenic cytokines and an increase in atheroprotective cytokines [12]. (See "C-reactive protein in cardiovascular disease".)
RISKS — In addition to musculoskeletal injuries, regular exercise is associated with a number of potential, rare adverse effects (eg, arrhythmias, including sudden death, myocardial infarction [MI], and rhabdomyolysis) [13]. As an example, there is a transient increase in the risk of sudden death among healthy subjects associated with an episode of vigorous exercise. However, the absolute risk of sudden death during any particular episode of exercise is low (1 per 1.51 million episodes of exercise in the Physicians' Health Study) [14], and habitual exercise diminishes the risk of sudden death. The potential risks and noncardiac benefits of exercise are discussed separately. (See "The benefits and risks of aerobic exercise" and "Athletes: Overview of sudden cardiac death risk and sport participation" and "Mechanisms of acute coronary syndromes related to atherosclerosis".)
PRIMARY PREVENTION — A number of studies have shown a strong inverse relationship between leisure time activity and energy expenditure, habitual exercise, and fitness and the risk of coronary disease and death (table 2) [15-38]. Although most observations were made in men, a similar cardiovascular benefit from exercise and fitness has been found in women [15,16,25-29], across different racial groups [26,35], in older adult patients [38], and in different countries around the world [35,39].
Relation to exercise — The overall benefit of exercise on the risk of myocardial infarction (MI) was demonstrated in a report from the INTERHEART study of patients from 52 countries; regular physical activity was associated with an odds ratio for first MI of 0.86 [35]. Lack of such activity accounted for 12 percent of the population-attributable risk.
The range of findings on the beneficial effects of exercise in different groups can be illustrated by the following observations.
Men — Physical activity habits were analyzed in 10,269 Harvard alumni (mean age 58) in a retrospective study over 12 years [19-21]. Those men who engaged in moderately vigorous sports activity (defined as total physical activity levels >4200 kJ/week or brisk walking, recreational cycling or swimming, home repair, and yard work for 30 minutes per day on most days) had a 23 percent lower risk of death than those who were less active. The improvement in survival with exercise was equivalent and additive to other lifestyle measures such as cessation of smoking, control of hypertension, and avoidance of obesity. This reduction in risk was also seen in men with multiple coronary risk factors [20].
Regular walking also appears to be beneficial in older men. This was illustrated in a report from the Honolulu Heart Program of 707 retired nonsmoking men (mean age 69) who were capable of participating in a low-intensity activity on a daily basis [40]. The distance walked was measured at baseline and mortality data, then collected over a 12-year period. After adjustment for age, men who walked more than two miles per day (range two to eight miles [3.2 to 12.8 km]) had a significantly lower mortality rate than those who walked less the one mile (1.6 km) per day (23.8 versus 40.5 percent, risk factor adjusted relative risk [RR] 1.8).
The individual's perception of the intensity of physical activity also appears to affect risk. In a review of 7337 men (mean age 66 years) who were followed for a mean of 5.3 years [22], the men who perceived their exercise intensity as moderate or strong had a significant reduction in their adjusted risk of coronary heart disease (CHD) compared with those who perceived their exercise intensity as weak or less intense (RR 0.66 to 0.72). This relationship applied even to men who were not fulfilling the current recommendations for exercise intensity and duration.
Women — The Nurses' Health Study of 72,488 women between 40 and 65 years of age found that brisk walking or vigorous exercise was inversely related to the risk of a coronary event; in a multivariate analysis, women in increasing quintile groups for energy expenditure had age-adjusted RRs for coronary events of 0.88, 0.81, 0.74, and 0.66, indicating a graded benefit from exercise [25]. Sedentary women who became active in mid-life or later had a lower incidence of coronary events compared with those who remained inactive.
Virtually identical findings were noted in a review of over 70,000 postmenopausal women in the Women's Health Initiative Observational Study in which prolonged sitting predicted an increase in cardiovascular risk [26].
Healthy women also benefit from light to moderate exercise; the benefit is again related to the duration of exercise. This was demonstrated in a review of almost 40,000 healthy women (mean age 54 years) in the Women's Health Study [27]. With a multivariate analysis, the RRs of CHD for walking 1 to 59 minutes, 1 to 1.5 hours, and 2 or more hours per week were 0.86, 0.49, and 0.48, respectively; there was no association with walking pace.
Twins — The Finnish Twin Cohort study of almost 8000 same-sex twin pairs found an odds ratio for death of 0.66 in occasional exercisers and 0.44 in conditioning exercisers compared with their sedentary twins [24]. Conditioning exercisers were defined as those who reported exercising at least six times per month with an intensity corresponding to at least vigorous walking for a mean duration of 30 minutes.
Type, intensity, and duration of exercise — Because of variations in ability, interest, and lifestyle, there is no exercise prescription that will satisfy all patients. However, compared with no exercise, virtually any type of exercise is beneficial, with as little as one hour per week providing substantial benefits on the risk of CHD and mortality [31,41].
●In a cohort of 44,452 men (age 40 to 75) enrolled in the Health Professionals' Follow-up Study (475,755 patient-years of follow-up), several types of physical activity were associated with a significant reduction in CHD risk [31]:
•Running for one hour or more per week – RR 0.58; 95% CI 0.44-0.77
•Rowing for one hour or more per week – RR 0.82; 95% CI 0.68-0.99
•Brisk walking for 30 minutes or more per day – RR 0.82; 95% CI 0.67-1.00
•Lifting weights for 30 minutes or more per week – RR 0.77; 95% CI 0.61-0.98
●In the Aerobics Center Longitudinal Study, a prospective observational cohort study of 55,137 persons (mean age 44 years; 26 percent women), participants were asked to complete a four-question survey upon enrollment regarding the duration, distance, frequency, and speed of any running or jogging that they performed [41]. After a mean follow-up of nearly 15 years, runners had a significantly lower risk of all-cause and cardiovascular mortality compared with non-runners (hazard ratios [HR] 0.70 [95% CI 0.64-0.77] and 0.55 [95% CI 0.46-0.65], respectively). Additionally, the derived mortality benefit was similar for all runners regardless of the participant's total running time, including for those participants who ran less than 51 minutes per week.
Both studies are consistent in showing a significant reduction in risk of cardiovascular disease (CVD) and mortality with as little as one hour of moderate or high exertion per week.
We encourage exercise according to the 2019 American College of Cardiology/American Heart Association (ACC/AHA) Guideline on the Primary Prevention of Cardiovascular Disease which recommends that adults accumulate at least 150 minutes of moderate-intensity physical activity per week or at least 75 minutes of vigorous-intensity physical activity per week to reduce the risk of atherosclerotic cardiovascular disease (ASCVD). If unable to meet this minimum physical activity recommendation, doing at least some of the moderate- or vigorous-intensity activity is beneficial in reducing ASCVD risk. Adults in the United States spend on average >7 hours per day sedentary. Decreasing sedentary time and replacing it with other physical activity is recommended [42]. Even a small amount of exercise is better than no exercise.
Nevertheless, greater exercise is associated with larger cardiovascular benefits, as demonstrated in studies showing greater increases in HDL cholesterol and decreases in adiposity, serum triglycerides, and CHD risk with longer distances among runners [43,44].
A considerable body of evidence suggests that high-intensity interval training (HIIT) in adults, defined as intense bouts of exercise that elicit ≥80 percent maximal heart rate, interspersed by periods of lower-intensity exercise or by rest, improves cardiometabolic health in a time-efficient manner. HIIT cardiometabolic benefits are superior or at least comparable to the traditional moderate-intensity continuous exercise [45,46]. At least 12 weeks of HIIT has been shown to significantly improve aerobic capacity (maximum oxygen uptake), resting blood pressure, heart rate, and waist circumference and percent body fat in overweight/obese population [46].
Relation to fitness — In addition to the amount of exercise, the degree of cardiovascular fitness, as determined by the duration of exercise and maximal oxygen uptake on a treadmill compared with age- and sex-specific normal values, is also associated with a reduction in CHD risk and overall and cardiovascular mortality [15,17,22,28,29,32-34,36,37,47,48]. Although early-phase clinical trials show significant cardiometabolic benefits of HIIT, long-term clinical trials to investigate the effects of HITT on morbidity and mortality are warranted.
This section will emphasize studies evaluating the relationship between fitness and long-term outcomes in asymptomatic adults. The importance of exercise capacity when exercise testing in performed in patients with known or suspected CHD is discussed separately. (See "Prognostic features of stress testing in patients with known or suspected coronary disease", section on 'Exercise capacity'.)
Men — The importance of fitness in men has been illustrated in numerous observational studies, all of which have shown an inverse relationship between level of fitness and mortality [17,34,36,47,49]. In the largest study, 18,102 men (mean age 58.4 years) underwent a symptom-limited exercise test without evidence of ischemia between 1986 and 2011 and were followed for a median of 10.8 years [49]. A threshold group of patients were identified whose level of fitness was associated with no change in mortality (compared with the general population), with all-cause mortality inversely and significantly associated with level of fitness as follows:
●Least fit – >2 metabolic equivalents (METs) below threshold (HR for mortality 1.52; 95% CI 1.39-1.67)
●Low-fit – 0 to 2 METS below threshold (HR 1.21; 95% CI 1.12-1.31)
●Moderate-fit – 0 to 2 METS above threshold (HR 0.71; 95% CI 0.65-0.78)
●Fit – 2.1 to 4 METs above threshold (HR 0.62; 95% CI 0.54-0.70)
●Most fit – >4 METs above threshold (HR 0.46; 95% CI 0.39-0.55)
For each additional in exercise capacity of 1 MET, mortality risk was 12 percent lower. Age-specific exercise thresholds identifying fitness were established in this cohort and serve as a useful guide to interpreting a patient's level of fitness following a standard exercise test:
●Age <50 years – 8 to 9 METs
●Age 50 to 59 years – 7 to 8 METs
●Age 60 to 69 years – 6 to 7 METs
●Age ≥70 years – 5 to 6 METs
Women — Similar benefits from fitness have been described in women [15,16,28,29,47,48,50]. The magnitude of this effect is illustrated by the following observations.
A report from a Lipid Research Clinics study included 2994 asymptomatic women (mean age 47) who underwent exercise testing at study entry and were then followed for 20 years [28]. There were 427 deaths (14 percent), of which 147 (5 percent) were due to cardiovascular causes. Exercise-induced ST segment depression (≥1.0 mm) did not increase the risk of cardiovascular death (age-adjusted HR 1.02). By contrast, women who were below the median for either exercise capacity or heart rate recovery, both of which were considered measures of fitness, were at increased risk: those below the median for both variables were at highest risk (multivariable-adjusted HR 3.5 compared with those above the median for both variables).
In a study from the St James Women Take Heart Project, 5721 asymptomatic women (mean age 52) underwent a symptom-limited, maximal stress test [29]. A nomogram was developed, based upon age and achieved exercise capacity in METs (calculated from the speed and degree of incline of the treadmill), that permitted estimation of the percentage of predicted exercise capacity.
Predicted exercise capacity in METs = 14.7 - (0.13 x age)
This formula was validated in a referral cohort of 4471 women with cardiovascular symptoms. The predicted value was somewhat different in self-reported active and sedentary women.
At follow-up, the outcome was significantly worse in women who achieved less than 85 percent of age-predicted value compared with the remaining women:
●Among asymptomatic patients, the HRs were 2.03 for all-cause mortality and 2.44 for cardiac mortality.
●Among symptomatic patients the respective HRs were 2.37 and 2.02.
Interaction with other exercise parameters — Exercise capacity on an exercise stress test interacts with other parameters of risk (as estimated from multifactorial risk scores, such as the Framingham risk score), and with other predictive parameters on exercise testing. These issues are discussed in detail separately. (See "Prognostic features of stress testing in patients with known or suspected coronary disease".)
Younger patients — The above findings were primarily made in middle-aged patients and it seems likely that the effects of fitness, as estimated from exercise test results, begin earlier. This was confirmed in a population-based cohort study of over 5000 adults 18 to 30 years of age, which demonstrated a relationship between fitness and the development of cardiovascular risk factors at 15-year follow-up [37].
The following findings were noted:
●During follow-up, new-onset diabetes, hypertension, and the metabolic syndrome developed at a rate of 0.3, 1.3, and 1.0 percent per year, respectively. Individuals with low fitness (<20th percentile) were three- to sixfold more likely to develop diabetes, hypertension, and the metabolic syndrome than individuals with high fitness (≥60th percentile). The level of fitness was less clearly related to the development of hypercholesterolemia.
●Almost 2500 subjects repeated the exercise test at seven years. Improved fitness was associated with reductions in the rate of developing diabetes and the metabolic syndrome; the significance of these changes was only partially accounted for by changes in weight.
Older patients — Measuring fitness by maximal exercise testing may be more difficult to achieve in older adults due to musculoskeletal and other limitations. A possible alternative is performance on a long-distance corridor walk. This was assessed in a study of 3075 community-dwelling adults who were 70 to 79 years of age [51]. The patients were instructed to walk 400 m (about one-quarter of a mile) with encouragement at each lap. At a mean of 4.9 years, participants who failed to complete the walk were at significantly greater risk for developing mobility limitation and mobility disability, with a trend toward increased mortality. Among those who completed the test, each additional minute required was associated with significant increases in mortality and incident CVD (adjusted HR 1.29 and 1.20, respectively) as well as mobility limitation and disability. The adjusted HR for death was 3.63 in the lowest compared with best quartile of functional capacity (>362 versus <290 seconds).
Metabolic syndrome — Metabolic syndrome is a high-risk phenotype associated with impaired glycemic control (due to insulin resistance), hypertension, dyslipidemia, and abdominal obesity. (See "Metabolic syndrome (insulin resistance syndrome or syndrome X)".)
The relationship between fitness and development of metabolic syndrome was directly addressed in a prospective study of 9007 men and 1491 women who did not have the metabolic syndrome at baseline [52]. At a mean follow-up of 5.7 years, metabolic syndrome developed in 15 percent of the men and 3.8 percent of the women. The likelihood of developing metabolic syndrome was significantly lower in the middle and upper thirds of fitness in men (adjusted HRs 0.74 and 0.47, respectively) and in the upper third of fitness in women (adjusted HR 0.37).
The association between changes in activity level and the development of CVD in persons with impaired glucose tolerance has also been studied. In the NAVIGATOR trial of 9306 persons with impaired glucose tolerance who also had either known CVD or at least one other risk factor for CVD, higher levels of baseline ambulatory activity (HR 0.90 per 2000 steps of baseline daily activity; 95% CI 0.84-0.96) as well as increases in ambulatory activity during the trial (HR 0.92; 95% CI 0.86-0.99) were both inversely associated with risk of CVD [53].
Exercise testing — Because of the frequency of false-positive tests, the role of exercise testing in screening asymptomatic individuals has been controversial [54,55]. The settings in which screening might be performed are discussed in detail separately. The 2002 ACC/AHA guidelines on exercise testing concluded that the weight of evidence or opinion was in favor of the usefulness of exercise testing in asymptomatic persons with diabetes mellitus who plan to start vigorous exercise [56]. The evidence was considered less well-established for screening asymptomatic men over age 45 and women over age 55 who plan to start vigorous exercise, particularly if sedentary. (See "Screening for coronary heart disease".)
SECONDARY PREVENTION — There are a number of observations suggesting that exercise and fitness are also beneficial in patients who have coronary heart disease (CHD) [9,34,57-60]. As an example, one study of 772 men (mean age 63) with documented CHD who were followed for up to five years found that the lowest incidence of all-cause and cardiovascular mortality was seen in those who engaged in light and moderate activity; this activity included recreational (nonsporting) activity (≥4 hours/week), regular walking (>40 minutes per day), or moderate or heavy gardening (adjusted relative risk [RR] 0.42 and 0.47 compared with inactivity or occasional light activity) [59].
A 2005 meta-analysis evaluated trials of cardiac rehabilitation (including exercise with or without risk factor education) among patients with coronary disease (most post-myocardial infarction [MI]) [57]. (See "Cardiac rehabilitation: Indications, efficacy, and safety in patients with coronary heart disease".)
The following findings were noted:
●Exercise rehabilitation alone produced a significant reduction in all-cause mortality (6.2 versus 9.0 percent, summary risk ratio 0.72, 95% CI 0.54-0.95) and an almost significant reduction in recurrent MI (summary risk ratio 0.76, 95% CI 0.57-1.01).
●A combined program of exercise rehabilitation and risk factor education produced an almost significant reduction in all-cause mortality (9.3 versus 10.8 percent, summary risk ratio 0.88, 95% CI 0.74-1.04) and a significant reduction in recurrent MI (summary risk ratio 0.62, 95% CI 0.44-0.87).
●The overall mortality benefit from cardiac rehabilitation was present at two years (summary risk ratio 0.53, 95% CI 0.35-0.81) but not at one year.
Resistance training is beneficial in patients with stable coronary artery disease. While it is typically studied in combination with aerobic training, resistance training independently increases muscle strength and endurance performance, and the combination of resistance and aerobic training outperforms aerobic-only training for outcomes of muscle strength, work capacity, VO2max, fat mass, and fat-free mass [61,62]. The data do not show an increased rate of adverse effects (dysrhythmia, worsening of ejection fraction, hypertension, or angina) resulting from resistance training, even in those undergoing cardiac rehabilitation following acute myocardial infarction [63]. (See "Strength training for health in adults: Terminology, principles, benefits, and risks".)
Almost all patients with stable coronary artery disease, including those who have attended a cardiac rehabilitation program, derive benefit from life-long regular physical activity. The American College of Cardiology/American Heart Association (ACC/AHA) guidelines for the management of patients with chronic stable angina reached the following conclusions [64]:
●The patient's risk should be assessed with a physical activity history, and in some cases an exercise test. For patients who are stable, but recently hospitalized for acute coronary syndrome, the 2002 ACC/AHA Guideline Update for Exercise Testing recommended an exercise test for activity prescription either before discharge (submaximal exercise tolerance test), early after discharge (symptom limited at 14 to 21 days), or late after discharge (symptom limited at three to six weeks) if an early exercise test was submaximal [56]. Performance of an exercise tolerance test was given a less strong recommendation for patients who have undergone coronary revascularization.
●In the absence of a contraindication, moderate intensity aerobic activity is recommended for 30 to 60 minutes, five to seven days a week.
●Physical activity to include resistance training on two days a week was given a weaker recommendation.
THE EXERCISE PRESCRIPTION — In 2018, the US Department of Health and Human Services issued guidelines for healthy activity levels in adults and older adults [65]. The benefits of physical activity include lower cardiovascular disease mortality and cardiovascular disease (CVD). Only moderate-intensity exercise is required for certain cardiovascular health benefits such as a reduction in blood pressure and elevation in high-density lipoprotein [HDL] cholesterol, in contrast to the higher intensities necessary for substantial gains in aerobic fitness [66,67]. Details on how to prescribe an exercise program are provided elsewhere. (See "Exercise prescription and guidance for adults", section on 'Prescribing an exercise program'.)
For patients who have had an acute myocardial infarction, the components of an exercise rehabilitation program are described in detail elsewhere. The degree of activity depends upon an assessment of risk, such as the presence or absence of ischemia, arrhythmia, or heart failure. (See "Cardiac rehabilitation programs".)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Lifestyle management and cardiac rehabilitation".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Exercise and movement (The Basics)")
●Beyond the Basics topic (see "Patient education: Exercise (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Physical exercise is likely to lower cardiovascular disease (CVD) risk based upon strong, consistent epidemiologic evidence and moderately strong supporting evidence from clinical trials. (See 'Limitations of the evidence' above.)
●Regular physical activity is recommended throughout life. We encourage at least 150 minutes per week of accumulated moderate-intensity physical activity or 75 minutes per week of vigorous-intensity physical activity. If unable to meet this minimum physical activity recommendation, doing at least some of the moderate- or vigorous-intensity activity is beneficial in reducing atherosclerotic CVD (ASCVD) risk. High-intensity interval training (HIIT) performed at least three times per week offers superior cardiometabolic health benefits. In those unable to achieve this exercise recommendation for any reason, we encourage physical activity at lower intensity or for a shorter duration as this is preferable to remaining sedentary. (See 'Type, intensity, and duration of exercise' above.)
●Exercise and fitness are also beneficial in patients who have coronary heart disease (CHD) based on observational data. (See 'Secondary prevention' above.)
●Despite the benefits of an exercise program, there are risks, even in trained athletes. As a result, the American Heart Association (AHA) published a scientific statement outlining a risk classification of patients for exercise training (table 3A-D) and contraindications for exercise testing and training (table 4) [68]. (See "The benefits and risks of aerobic exercise" and "Athletes: Overview of sudden cardiac death risk and sport participation".)
ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Pamela Douglas, MD, who contributed to an earlier version of this topic review.
