Exercise and Cardiovascular Risk Reduction (Opinion)
- Eijsvogels TM, Molossi S, Lee DC, Emery MS, Thompson PD.
- Exercise at the Extremes: The Amount of Exercise to Reduce Cardiovascular Events. J Am Coll Cardiol 2016;67:316-329.
Habitual physical activity and exercise training reduce cardiovascular morbidity and mortality. However, several recent reports suggested that high volumes of aerobic exercise may be as bad for cardiovascular outcomes as physical inactivity; public media embraced the idea that exercise may be harmful and disseminated this message, diverting attention from the benefits of exercise as a potent intervention in the primary and secondary prevention of heart disease. This review article, authored by the American College of Cardiology Sports and Exercise Cardiology Leadership Council, reviews literature addressing the volume and intensity of aerobic exercise for primary and secondary risk reduction, and addresses whether there is a volume of exercise that increases cardiovascular disease risk. The following are points to remember:
- The 2008 Physical Activity Guidelines recommend 150 minutes per week of moderate-intensity or 75 minutes per week of vigorous-intensity aerobic exercise for all adults in the United States; however, only one half of Americans meet those guidelines.
- Primary prevention:
- There is a strong and consistent relationship between increasing physical activity and graded cardiovascular risk reduction.
- Cardiovascular risk reduction with increasing physical activity likely is mediated by mechanisms including improved triglyceride and high-density lipoprotein cholesterol levels, lower blood pressure, improved glucose metabolism and insulin sensitivity, lower body weight, and reduced inflammatory markers (accounting for ~59% reduction in risk); and improved endothelial function, enhanced vagal tone, and vascular remodeling (potentially explaining the other 41% of risk reduction).
- There is a strong dose-response relationship between increasing physical activity and decreased cardiovascular mortality, including standing versus sitting, and moderate and vigorous physical activity within guideline recommendations. That even low volumes of exercise can effectively reduce cardiovascular mortality is a message that clinicians should communicate to stimulate physical activity among vulnerable populations.
- Combined data suggest that maximal cardiovascular mortality risk reduction is found at an exercise volume of 41 MET-hours/week, which is 3.5-4 times greater than the guideline-recommended volume; and equals 547 minutes (9.1 hours) per week of moderate-intensity exercise at 4.5 METS, or 289 minutes (4.8 hours) per week of vigorous-intensity exercise at 8.5 METS.
- High-intensity (≥6.0 METS) interval training produces greater improvement in cardiorespiratory fitness compared to moderate-intensity (3.0-5.9 METS) sustained activities, and higher fitness levels are in turn associated with lower cardiovascular and all-cause mortality.
- The dose-response relationship between physical activity and mortality appears to be different for moderate and for vigorous exercise. Increasing volumes of moderate-intensity exercise are associated with further improvements in cardiovascular risk reduction, whereas lower volumes of vigorous-intensity exercise (11 MET-hours/week) are associated with maximal cardiovascular risk reduction. However, there is not an upper limit of exercise-induced health benefits; increasing volumes of moderate- and vigorous-intensity aerobic exercise reduces all-cause and cardiovascular mortality compared to physical inactivity.
- Secondary prevention:
- American College of Cardiology/American Heart Association guidelines provide recommendations for exercise among patients with specific cardiovascular conditions, including patients with congenital heart disease, heart failure, non–ST-elevation acute coronary syndromes, and ST-segment elevation myocardial infarction.
- Patients with stable angina pectoris, systolic heart failure, myocardial infarction, or recent cardiac surgery or percutaneous coronary intervention are eligible for cardiac rehabilitation, which includes exercise training; nutritional and psychological counseling; weight, blood pressure, lipid, and diabetes management; and smoking cessation.
- Supervised high-intensity interval training protocols yield larger health improvements than moderate-intensity continuous training protocols, with low but present risk for cardiac arrest and sudden cardiac death during exercise. Among patients with cardiac known disease, moderate-intensity exercise at volumes comparable to guidelines are recommended.
- Controversy regarding excessive exercise:
- Various studies have reported potentially adverse effects of exercise (including troponin elevation, myocardial fibrosis, transient cardiac dysfunction, arrhythmias, coronary artery calcification, and increased cardiovascular mortality). However, many of the nonclinical markers (troponin elevation, transient cardiac dysfunction, coronary calcification) may not be markers of actually increased clinical risk.
- Two recent epidemiological studies reported a U-shaped relationship between aerobic exercise volumes and cardiovascular morbidity and mortality in a general population. However, methodological limitations of both studies make it premature to conclude that high exercise volumes increase cardiovascular risk compared to light-to-moderate volume.
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