Barry A. Franklin, PhD, on Exercise and Cardiovascular Health
It is well known that exercise can reduce the risk for cardiovascular disease (CVD) and improve overall health. But what types of exercise are appropriate for patients at each stage of CVD risk?
This was one topic of discussion during the 2019 American Society for Preventive Cardiology Congress on CVD Prevention. Presenter Barry A. Franklin, PhD, who is the director of preventive cardiology and cardiac rehabilitation at Beaumont Health in Royal Oak, Michigan, and a professor of internal medicine at the Oakland University William Beaumont School of Medicine, answered our questions about his session.1
CARDIOLOGY CONSULTANT: What types of exercise are the best for cardiovascular health? Why are they the best?
Barry Franklin: Both regular endurance activity (e.g., walking, jogging, bicycling) and higher levels of cardiorespiratory fitness (CRF), expressed as metabolic equivalents (METs; 1 MET = 3.5 mL O2/kg/min), are associated with a reduced risk of developing chronic diseases, including CVD. Each 1-MET increase in exercise capacity is associated with an approximate 15% reduction in mortality in patients with and without heart disease. Indeed, a recent landmark study reported that the most physically active cohorts of men and women demonstrated 7- to 8-year gains in life expectancy.
Although arterial dysfunction has been widely considered a marker of age-associated CVD, regular aerobic exercise inhibits large artery stiffening and preserves endothelial function. Increased CRF in middle-age is also associated with a lower risk of developing heart failure, regardless of the body mass index. Aerobic exercise should be complemented with flexibility and resistance training. Why? Flexibility calisthenics are associated with a reduced risk for musculoskeletal injury (strains and sprains), whereas chronic resistance exercise (i.e., weight training) has been shown to be superior to aerobic exercise in increasing bone mineral density, muscle mass, strength, insulin sensitivity, and the basal metabolic rate. Other recent studies have shown that by increasing patients’ muscle strength, they can reduce the rate-pressure product (and cardiac demands) when lifting or carrying any given object.
CARDIO CON: In which patient populations are these types of exercise indicated?
BF: Over the last 2 decades, considerable evidence from large and well-designed epidemiologic studies with diverse populations supports the preventive role of regular moderate- to vigorous-intensity exercise and improved CRF on reducing the incidence and severity of hypertension, type 2 diabetes, atrial fibrillation, chronic kidney disease, and major cardiovascular events including heart failure, myocardial infarction, and the need for coronary revascularization. Numerous studies have also shown that low-fit individuals are about 2 to 3 times more likely to die in follow-up compared with their more-fit counterparts, regardless of the risk factor profile or the presence of coronary artery calcium, signifying subclinical coronary artery disease.
In contrast, vigorous- to high-intensity physical activity in individuals with some congenital or structural cardiovascular abnormalities (e.g., Marfan syndrome, inherited cardiomyopathies, and arrhythmic syndromes such as arrhythmogenic right ventricular cardiomyopathy) are generally contraindicated. Such activities, as well as heavy resistance training are also contraindicated in patients with previous aortic dissection. Though these patients should generally be discouraged from participating in highly competitive and/or strenuous endurance exercise, they should be encouraged to engage in leisure-time, low- to moderate-intensity physical activity.
CARDIO CON: How much exercise is recommended for people within different risk categories?
BF: Collectively, research studies indicate that health benefits are realized at relatively moderate levels of exercise or physical activity and increase in a dose-response fashion, up to a point. In other words, any physical activity is better than none, moderate-intensity physical activity (40% to 60% functional capacity) is better than low-intensity, and vigorous physical activity (≥60% functional capacity) appears to be superior to moderate-intensity exercise in promoting health benefits. However, patients should be counseled to augment their CRF by starting with level walking at a 2 to 3 mph pace and gradually progress to more vigorous exercise, provided they remain asymptomatic.
Although some studies suggest that high-intensity interval training elicits slightly greater increases in CRF than moderate-intensity training (~.5 MET), concerns regarding the safety of high-intensity interval training in “at-risk” patients suggest that it should be cautiously prescribed.
In summary, for most patients, substantial health benefits result from 2.5 hrs/wk of moderate-intensity physical activity or 1.25 hrs/wk of vigorous exercise. These doses correspond to about 500 to 1000 MET-mins/wk. Aerobic activity can be performed in shorter bouts (e.g., 5-10 mins) that are repeated and accumulated throughout the day and complemented by resistance/flexibility training.
CARDIO CON: Can you comment on the age-old question, “How much exercise is too much?”
BF: Vigorous physical activity, particularly when performed by unfit individuals with known or occult CVD, can acutely increase the risk of sudden cardiac death and acute myocardial infarction. The most common cause of exercise-related sudden cardiac death in middle-aged and older adults is atherosclerotic coronary artery disease. In contrast, the most common cause in young individuals is controversial. Although previous studies have reported that structural cardiovascular abnormalities, most notably, hypertrophic cardiomyopathy, were the underlying problem, recent studies suggest that sudden cardiac death with a structurally normal heart, and not hypertrophic cardiomyopathy, may be another common cause.
Other recent studies have also shown that high-volume, high-intensity exercise regimens are associated with potential cardiac maladaptations, including accelerated coronary artery calcification, exercise-induced biomarker release, myocardial fibrosis, and atrial fibrillation. Though coronary artery atherosclerosis may be more prevalent in middle-aged athletes compared with inactive controls, with the highest plaque prevalence in the most active athletes, this finding is not associated with increased cardiovascular events. Numerous investigations have also now reported that extreme endurance training, over time, is strongly linked to pathological remodeling, often leading to lone atrial fibrillation. Additionally, exercise is reported to accelerate CVD development and severity in patients with arrhythmogenic right ventricular cardiomyopathy. The relationship between these maladaptive responses and physical activity is often descripted by a U- or reverse-J–shaped dose-response curve. Finally, these studies, and other recent reports, suggest that the added survival benefits of vigorous physical activity (i.e., running) appear to plateau beyond 35 to 40 mins/d.
CARDIO CON: What is your key take-home message for cardiologists?
BF: In aggregate, an escalating number of research studies now support the recommendation that regular moderate to vigorous physical activity should be promoted by health care professionals (e.g., internal medicine physicians, cardiologists, nurses, physician assistants) for optimal health. In addition to the well-established survival benefit, increased levels of habitual physical activity prior to hospitalization for acute coronary syndromes are also associated with better short-term cardiovascular outcomes. In contrast, individuals with low levels of CRF have higher annual health care costs and higher rates of surgical complications.
Despite the numerous salutary effects, exercise is a double-edged sword in that it can both protects against and provokes acute cardiac events. For the vast majority of the population, the benefits outweigh the risks. Inactive patients should be strongly encouraged to start a walking program and progressively increase the exercise intensity (i.e., walking speed), provided they remain asymptomatic. Exertion-related symptoms suggest immediate cessation of exercise and prompt medical review. Selected patient subsets should avoid high-volume, high-intensity exercise regimens as well as superimposed environmental and/or competitive stressors. Finally, extreme exercisers should be appropriately screened for structural cardiovascular abnormalities, most notably, hypertrophic cardiomyopathy, and atherosclerotic CVD, which have been strongly linked to numerous marathon and triathlon deaths. Several major medical centers, including Massachusetts General Hospital and Beaumont Health (Royal Oak, MI) have developed specialized Cardiovascular Performance Clinics for this purpose.
- Franklin B. Exercise and cardiovascular health: how much and what kind? Talk presented at: 2019 American Society for Preventive Cardiology Congress on CVD Prevention; July 19-21, 2019: San Antonio, TX. https://www.aspconline.org/wp-content/uploads/2019/05/ASPC-2019Mtg-Program-v3-0419.pdf.