Coronary Heart Disease and the Benefits of Regular Exercise
According to the American Heart Association, physical inactivity ranks high among risk factors associated with coronary heart disease, the number one cause of death in the United States. In fact, inactive individuals are at twice the risk of developing coronary heart conditions than those who exercise three times per week for at least 20 minutes.
Accordingly, the increased coronary risk linked to physical inactivity is similar to the increased risk associated with elevated cholesterol levels, elevated blood pressure or smoking a pack of cigarettes each day. (There are, however, substantially more inactive individuals compared to the numbers who smoke, have high cholesterol or high blood pressure).
Since the benefits of starting an exercise program appear to be greatest in the most sedentary individuals, the largest reduction in coronary risk occurs when an inactive individual adopts even a modest fitness lifestyle.
Just 20 minutes of moderate intensity aerobic exercise, three times per week is needed to receive major health benefits.
- Any continuous, rhythmic, activity that uses large muscle groups
How Does Exercise Reduce Coronary Risk?
There are a number of reasons physical activity works to reduce the risk of coronary heart disease including:
- Increases HDL-C–Exercise has been found to be useful in increasing high-density lipoprotein cholesterol. Recent studies have reported significant increases in HDL-C (between 5% and 15%) following aerobic exercise training.
- Controls mild and moderate hypertension—A recent review of 25 long-term studies concluded that aerobic exercise training leads to reductions in systolic and diastolic blood pressure.
- Decreases the risk of diabetes—Regular physical activity can help manage and even prevent noninsulin-dependent diabetes mellitus.
- Reduces excess body weight—Excess weight increases coronary risk. Regular exercise increases daily caloric expenditure.
- Other benefits—These may include resistance to lethal cardiac arrhythmias and a reduced risk of coronary thrombosis, which may be due to a reduction in platelet adhesiveness and the ability to aggregate, as well as increased fibrinolysis.
Are There Risks Associated With Exercise?
The major health risks of exercise training are muscle and joint injuries and sudden cardiac death. Cardiac deaths during exercise are highly publicized but they actually don’t happen very often. In one study of male joggers, it was found that there was only one death per year among 15,620 seemingly healthy individuals. The rate of muscle and joint injuries among people who exercise on a recreational basis also is not very high. One study estimated that injuries requiring medical care occur at an annual rate of less than 5.14%.
Risks can be reduced however, if an exercise regimen is introduced gradually, within the physical limitations of an individual.
Guidelines for Safe Exercise
For the typical inactive individual, there are a number of steps that should be followed to minimize the risks of exercise.
- A physician should conduct a complete medical evaluation. This may include a stress test to evaluate for increased coronary risk.
- Individuals may begin moderate exercise programs (i.e., activities within the current capacity that can be sustained comfortably for a prolonged period), without exercise testing, as long as he or she starts gradually and is alert to the development of unusual signs or symptoms. Men over the age of 40, and women over the age of 50, should have a maximal exercise test before beginning a vigorous exercise program, as well as individuals at any age who are at high coronary risk. High-risk adults include those with two or more major coronary risk factors (i.e., hypertension, smoking, hyper cholesterolemia, diabetes and family history) and/or symptoms suggestive of lung, heart or metabolic problems (i.e., chest discomfort, shortness of breath with mild exertion, leg cramps, tachycardia).
The exercise program should be tailored to an individual’s needs and should also be designed to promote long-term compliance. The initial exercise program should be enjoyable and should not be painful or unduly stressful.
Anatomy of a Training Program
Based on guidelines established by the American College of Sports Medicine, a proposed fitness plan for cardiovascular health should meet the following criteria:
- Easily accessible
- Not too expensive
- Realistic based on an individual’s current fitness level
Any exercise program should also consist of a:
- 5-10 minute warm-up period that includes a short stretching program and low intensity exercises. This leads to greater flexibility, prepares the cardiovascular system for more intensive work and decreases musculoskeletal injury.
- An aerobic conditioning period lasting from 20-40 minutes that may include activities such as, brisk walking, jogging, swimming, bicycling, cross-country skiing, stepping or rowing. The duration of exercise depends on the intensity of the activity. Therefore, lower intensity activities should be performed over a longer period of time.
- 5-10 minute cool-down period that includes walking or pedaling against very low resistance, followed by a stretching period. (This will prevent venous pooling, which may lead to hypotension, lightheadedness or syncope. The cool-down period may also decrease the risk of arrhythmias after aerobic exercise and may help prevent muscle soreness).
Finding Your Target Heart Rate for Optimal Success
In order to get the most benefit from exercise for coronary heart health, it’s important to determine your “target zone” or range in which your heart rate should be during activity.
To estimate your target heart rate, first determine the maximal heart rate (either directly from a maximal exercise test or calculate as 220 minus your current age). Maximal heart rates should be multiplied by 65% and 85% to determine the lower and upper limits of your target zone. For example, a 40-year-old person would have an estimated maximal heart rate of 180 beats per minute (BPM) (220-40) and a target zone of 117 BPM to 153 BPM (180 x 0.65 and 180 x 0.85). For sedentary individuals starting an exercise program, using 45% and 65% of their maximal heart rate as the lower and upper limits can modify the initial target zone.
Exercising at lower limits enables greater numbers of individuals to enjoy health benefits by allowing them to incorporate daily activities such as, gardening, house cleaning and walking into their activity program.
A target heart rate zone should be determined before you begin an exercise program, and be used as a guide to make sure you are not exercising at too high or too low an intensity.
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