Learning how much exercise is enough can help you gain the benefits of physical activity effectively and safely

The heart in motion: learning how much exercise is enough can help you gain the benefits of physical activity effectively and safely

It’s a fact accepted by physicians and health organizations worldwide: Regular exercise is a key to preventing and helping to treat a variety of health conditions, including heart disease. But incorporating regular exercise often is easier said than done, and if you’re considering an exercise regimen, you may have several questions: How much is enough? What exercises should I do? How intensely should I exercise?

The answers depend on your condition and whether you have underlying health problems, especially heart disease or cardiovascular risk factors. If this applies to you, you should undergo an exercise test to determine what level of exercise is safe for you, as well as your optimal exertion level, before hitting the pavement, jumping in the pool or hopping on a bicycle. “We’re finding a threshold of activity for cardiovascular benefit, and there’s an optimal level for weight-management issues, as well,” said Gordon Blackburn, Ph.D., director of The Cleveland Clinic’s Preventive Cardiology and Rehabilitation Program.

THE EVIDENCE FOR EXERCISE

Aerobic exercise–activities like walking, jogging, swimming and biking that use large muscle groups repetitively for a sustained period–improves heart rate, blood pressure and your body’s use of oxygen, and reduces your risk of stroke, heart attacks and other cardiac problems, such as irregular heart rhythms (arrhythmias). Exercise also provides you better management of diabetes and weight, and it may help reduce triglycerides, a fat in the blood that, at elevated levels, is a risk factor for cardiovascular disease.

Conversely, physical inactivity is among several factors that raise your risk of heart disease and stroke. A recent study concluded that the life expectancy for sedentary people 50 years and older was 1.5 years shorter than for people engaging in regular physical activity, and more than 3.5 years shorter than for people with high physical activity levels. Researchers also found that avoiding a sedentary lifestyle increased the years that study participants lived free of cardiovascular disease.

Aerobic exercise can be described in terms of intensity, duration and frequency. The American Heart Association (AHA) recommends at least 30 minutes of aerobic physical activity (done all at once or in increments at least 10 minutes) at moderate intensity on most–referably all–days of the week. But, moderate-intensity exercise varies from person to person, depending on physical condition. Determining the use of specifics of how hard, how long and how frequently you should exercise may require an exercise (stress) test supervised by a cardiac specialist.

AN EXERCISE PRESCRIPTION

Most men younger than age 50 who have no orthopaedic, metabolic or cardiovascular problems don’t need an exercise test before they begin an exercise regimen, but they should still consult their doctor. If you’re over 50, and especially if you’ve been sedentary, you should seek an evaluation from your doctor and take a supervised exercise test. “It’s a good way to gauge your starting point, and your follow-up exercise tests will help you assess your improvement,” Dr. Blackburn said. The test will allow your doctor to determine your maximum heart rate and target heart rate zone during exertion, and to help prescribe an exercise program to match your physical condition.

Your heart rate, or pulse, is the number of times your heart beats in a minute, and a normal pulse for an adult at rest is 60 to 100 beats per minute. Moderate-intensity exercise equates to 60 to 80 percent of the maximum heart rate measured on the stress test. If you haven’t undergone a stress test, you can calculate your predicted maximum heart rate by subtracting your age from 220.

To monitor your heart rate and find out if you’re exercising within these parameters, stop exercising and measure your pulse by placing the tips of your index and second fingers on the palm side of your other wrist and pressing lightly. Using a watch or clock with a second hand, count the number of beats you feel for 10 seconds and multiply that number by 6 to determine your heart rate. If your pulse is higher than your target zone, slow your rate of exercise.

People at high risk for cardiovascular disease or heart attack, or those recovering from a heart attack or heart surgery, normally start exercising at a much lower intensity and in smaller increments, and gradually ramp up to a moderate intensity for them of about 45 minutes, 5 days a week.

To measure the intensity of your exercise, use the rated perceived exertion (RPE) scale, which rates exertion from 0 (no difficulty) to 10 (very, very heavy). For most people, exercising in the RPE range of 3 (moderate) to 4 (somewhat heavy) is appropriate. Another measure of exertion is the “talk test.” If you have significant difficulty carrying on a conversation while exercising, you probably need to slow down.

Research suggests that you need to burn at least 1,000 to 1,500 calories a week to gain cardiovascular benefit. In more practical terms, you burn 100 to 150 calories for every mile you travel on your feet, regardless of how quickly you cover the distance, so you need to walk about 10 miles a week to achieve cardiovascular benefit, according to Dr. Blackburn. To lose weight and maintain weight loss, you may have to burn up to 2,500 calories a week, equal to walking 15 to 20 miles a week. Different exercises require varying amounts of exertion, and the number of calories you burn increases accordingly. For example, you spend fewer calories per mile while biking, but you burn more calories per mile swimming because of the resistance the water offers.

Your strength wanes as you age, and you place more stress on your cardiovascular system every time you lift something. For this reason, an exercise program should include some strength or resistance training. As with aerobic activities, you should talk to your doctor and set guidelines before you begin strength training. Studies show that this training, when designed correctly, is safe for people with heart disease.

TIPS AND PRECAUTIONS

Preface any workout with a warm-up period of at least 5 minutes of a low-intensity version of the exercise you plan to do, such as a slow walk preceding a more intense pace. Follow your exercise with a cool-down of at least 2 to 5 minutes, returning to the same slower pace of the warm-up. Cooling your body down reduces your risk of a dangerous drop in blood pressure and dizziness, and can help minimize delayed muscle soreness felt 24 to 48 hours after your workout. You also should stretch before or after the exercise, but do it gently to avoid straining a muscle.

If you want to go for a walk, take a circular path around your home rather than an out-and-back route that takes you farther away. Carry a cellular phone to call for help if you need it, or if you have concerns, walk with a partner.

Stop exercising and consult your doctor if you experience pain or pressure that radiates from your chest to your neck and left arm, dizziness, an abnormal heart rhythm, nausea or shortness of breath.

WHAT YOU CAN DO

Here are some tips on starting an exercise regimen and precautions to take:

* If you’re over 0, and especially if you’ve been sedentary, take an exercise test supervised by a cardiac specialist.

* While exercising, stop and measure your pulse, using a watch or clock with a second hand. if your pulse is higher than your target heart rate, slow your rate of exercise.

* Use the “talk test.” if you have significant difficulty carrying on a conversation while exercising, you probably need to slow down.

* Warm up for at least minutes with a low-intensity version of the exercise you plan to do. Follow your exercise with a cool-down of at least to minutes. gently stretch before or after the exercise.

* If you take a walk, follow a circular path around your home rather than an out-and-back route that takes you farther away.

* Carry a cell phone to call for help if you need it, or walk with a partner.

* Stop exercising if you experience pain or pressure in your chest, neck and left arm, dizziness, abnormal heartbeats or shortness of breath.

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