Some types of activity will improve the condition of your heart and lungs if they are brisk, sustained and regular. Low-intensity activities do not condition the heart and lungs much. But they can have other long-term health benefits.

The columns below describe three types of activities and how they affect your heart.

Column A - These vigorous exercises are especially helpful when done regularly. To condition your heart and lungs, the AHA recommends that you do them for at least 30 minutes, three or four times a week, at more than 50 percent of your exercise capacity. (See target heart rate zones.) Other health experts suggest a shorter period for higher-intensity activities. These exercises can also burn up more calories than those that are not so vigorous.

Column B - These activities are moderately vigorous but still excellent choices. When done briskly for 30 minutes or longer, three or four times a week, they can also condition your heart and lungs.

Column C - These activities are not vigorous or sustained. They still have benefits - they can be enjoyable, improve coordination and muscle tone, relieve tension, and also help burn up some calories.

These and other low-intensity activities - like gardening, yard- work, housework, dancing and home exercise - can help lower your risk of heart disease if done daily.

The key to success

How do I begin?

The key to a successful program is choosing an activity (or activities) that you will enjoy. Even moderate levels of activity have important health benefits. Here are some questions that can help you choose the right kind of activity for you:

1. How physically fit are you?

If you've been inactive for a while, you may want to start with walking or swimming at a comfortable pace. Beginning with less strenuous activities will allow you to become more fit without straining your body. Once you are in better shape, you can gradually change to a more vigorous activity if you wish.

2. How old are you?

If you are over 40 and have not been active, avoid very strenuous programs such as jogging when you're first starting out. For the first few months, build up the length and intensity of your activity gradually. Walking and swimming are especially good forms of exercise for all ages.

3. What benefits do you want from exercising?

If you want the benefits of exercise that condition your heart and lungs, check the activities in columns A and B. These activities - as well as those listed in column C - also give you other benefits as described in this booklet.

4. Do you like to exercise alone or with other people?

Do you like individual activities such as swimming, team sports such as soccer, or two-person activities such as racquetball? How about an aerobics class or ballroom dancing? Companionship can help you get started and keep going. If you would like to exercise with someone else, can you find a partner easily and quickly? If not, choose another activity until you can find a partner.

5. Do you prefer to exercise outdoors or in your home?

Outdoor activities offer variety in scenery and weather. Indoor activities offer shelter from the weather and can offer the convenience of exercising at home as with stationary cycling. Some activities such as bench stepping, running in place or jumping rope can be done indoors or outdoors. If your activity can be seriously affected by weather, consider choosing a second, alternate activity. Then you can switch activities and still stay on your regular schedule.

6. How much money are you willing to spend for sports equipment or facilities?

Many activities require little or no equipment. For example, brisk walking only requires a comfortable pair of walking shoes. Also, many communities offer free or inexpensive recreation facilities and physical activity classes.

7. When can you best fit the activity into your schedule?

Do you feel more like being active in the morning, afternoon, or evening? Consider moving other activities around. Schedule your activity as a regular part of your routine. Remember that exercise sessions are spread out over the week and needn't take more than about 10 to 15 minutes at a time.

By choosing activities you like, you will be more likely to keep doing them regularly and enjoying the many benefits of physical activity.

How do I pace myself?

Build up slowly If you've been inactive for a long while, remember it will take time to get into shape. Start with low- to moderate-level activities for at least several minutes each day. See the sample walking program, for example. You can slowly increase your time or pace as you become more fit. And you will feel more fit after a few weeks than when you first started.

How hard should I exercise?

It's important to exercise at a comfortable pace. For example, when jogging or walking briskly you should be able to keep up a conversation comfortably. If you do not feel normal again within 10 minutes of stopping exercise, you are pushing yourself too much.

Also, if you have difficulty breathing, experience faintness or prolonged weakness during or after exercising, you are exercising too hard. Simply cut back.

If your goal is to improve the fitness of your heart and lungs, you can find out how hard to exercise by keeping track of your heart rate. Your maximum heart rate is the fastest your heart can beat. Exercise above 75 percent of your maximum heart rate may be too strenuous unless you are in excellent physical condition. Exercise below 50 percent gives your heart and lungs little conditioning.

Therefore, the best activity level is 50 to 75 percent of this maximum rate. This 50-75 percent range is called your target heart rate zone.

When you begin your exercise program, aim for the lower part of your target zone (50 percent) during the first few months. As you get into better shape, gradually build up to the higher part of your target zone (75 percent). After 6 months or more of regular exercise, you can exercise at up to 85 percent of your maximum heart rate - if you wish. However, you do not have to exercise that hard to stay in good condition.

To find your target zone, look for the age category closest to your age in the table below and read the line across. For example, if you are 30, your target zone is 95 to 142 beats per minute. If you are 43, the closest age on the chart is 45; the target zone is 88 to 131 beats per minute.

Your maximum heart rate is approximately 220 minus your age. However, the above figures are averages and should be used as general guidelines.

Note: A few high blood pressure medicines lower the maximum heart rate and thus the target zone rate. If you are taking high blood pressure medications, call your physician to find out if your exercise program needs to be adjusted.

To see if you are within your target heart rate zone, take your pulse immediately after you stop exercising.

1. When you stop exercising, quickly place the tips of your first two fingers lightly over one of the blood vessels on your neck (carotid arteries) located to the left or right of your Adam's apple. Another convenient pulse spot is the inside of your wrist just below the base of your thumb.

2. Count your pulse for 10 seconds and multiply by six.

3. If your pulse falls within your target zone, you're doing fine. If it is below your target zone, exercise a little harder next time. And if you're above your target zone, exercise a little easier. Don't try to exercise at your maximum heart rate - that's working too hard.

4. Once you're exercising within your target zone, you should check your pulse at least once each week during the first 3 months and periodically after that.

A special tip:

Some people find that exercising within their target zone seems too strenuous. If you start out lower, that's okay, too. You will find that with time you'll become more comfortable exercising and can increase to your target zone at your own rate.

How long should I exercise?

That depends on your age, your level of physical fitness, and the level of intensity of your exercise. If you are inactive now, you might begin slowly with a 10-15 minute walk or other short session, three times a week. As you become more fit, you can do longer sessions or short sessions more often.

If you're active already and your goal is to condition your heart and lungs, try for a minimum of 30 minutes at your target heart rate zone. Each exercise session should include:

Warm up 5 minutes

Begin exercising slowly to give your body a chance to limber up and get ready for more vigorous exercise. Start at a medium pace and gradually increase it by the end of the 5-minute warm-up period.

Note: With especially vigorous activities such as jumping rope, jogging or stationary cycling, warm up for 5-10 minutes by jumping rope or jogging slowly, warming up to your target zone. It is often a good idea to do stretching exercises after your warm-up period and after your exercise period. Many of these stretching exercises can be found in books on sports medicine and running. Below are three stretches you can use in your warm-up period and after your cook down period. Each of these exercises help stretch different parts of your body. Do stretching exercises slowly and steadily, and don't bounce when you stretch.

Wall push: Stand about 1 1/2 feet away from the wall. Then lean forward pushing against the wall, keeping heels flat. Count to 10 (or 20 for a longer stretch), then rest. Repeat one to two times. Palm touch: Stand with your knees slightly bent. Then bend from the waist and try to touch your palms to the floor. Count to 10 or 20, then rest. Repeat one to two times. If you have lower back problems, do this exercise with your legs crossed.

Toe touch: Place your right leg level on a stair, chair, or other object. With your other leg slightly bent, lean forward and slowly try to touch your right toe with right hand. Hold and count to 10 or 20, then repeat with left hand. Do not bounce. Then switch legs and repeat with each hand. Repeat entire exercise one to two times.

Exercising within your target zone 30-60 minutes

Build up your exercising time gradually over the weeks ahead until you reach your goal of 30-60 minutes. Once you get in shape, your exercising will last from 30 to 60 minutes depending on the type of exercise you are doing and how briskly you do it. For example - for a given amount of time, jogging requires more energy than a brisk walk. Jogging will thus take less time than walking to achieve the same conditioning effect. For two examples of how to build up to the goal of 30-60 minutes, see "Two Sample Exercise Programs".

Cool down 5 minutes

After exercising within your target zone, slow down gradually. For example, swim more slowly or change to a more leisurely stroke. You can also cool down by changing to a less vigorous exercise, such as changing from running to walking. This allows your body to relax gradually. Abrupt stopping can cause dizziness. If you have been running, walking briskly, or jumping rope, repeat your stretching and limbering exercises to loosen up your muscles.

How often should I exercise?

If you are exercising in your target zone, exercise at least three or four times per week (every other day). If you are starting with less intense exercise, you should try to do at least something every day.

Exercising regularly is one of the most important aspects of your exercise program. If you don't exercise at least three times a week, you won't experience as many of the benefits of regular physical activity as you could or make as much progress. Try to spread your exercise sessions throughout the week to maximize the benefits. An every-other-day schedule is recommended and may work well for you.

What if I miss a few sessions?

Whenever you miss a few sessions (more than a week), you may need to resume exercising at a lower level than before. If you miss a few sessions because of a temporary, minor illness such as a cold, wait until you feel normal before you resume exercising.

If you have a minor injury, wait until the pain disappears. When you resume exercising, start at one-half to two-thirds your normal level, depending on the number of days you missed and how you feel while exercising.

Whatever the reasons for missing sessions, don't worry about the missed days. Just get back into your routine and think about the progress you will be making toward your exercise goal.

Is there a top limit to exercising?

That depends on the benefits you are seeking.

Anything beyond 60 minutes daily of a vigorous or moderately vigorous activity, such as those in columns A and B, will result in little added conditioning of your heart and lungs. And it may increase your risk of injury.

If you want to lose extra pounds or control your present weight, there is no upper limit in that the longer you exercise, the more calories you burn off. But remember that the most effective weight loss program includes cuffing down on calories in addition to exercise.

Remember: How you exercise is just as important as the kind of activity you do. Your activity should be brisk, sustained and regular - but you can do it in gradual steps. Common sense and your body will tell you when you are exercising too long or too hard. Don't push yourself to the point where exercise stops being enjoyable.