By Richard Josephson, MD, as told to Stephanie Watson.

Back in the middle of the 20th century, there was a concern that people with cardiovascular disease could hurt themselves if they exercised. People with heart failure used to be confined to their bed for long periods of time. Now we know that exercise, when done safely, doesn't damage the heart. It can actually protect the heart and lower the chances of future problems.

In most people with heart failure, the main symptom is exercise intolerance, which people often describe as fatigue or shortness of breath. You may feel tired, be unable to work, or have trouble just walking down the street or around your home. Staying active can help your body work better.

While you can begin to exercise on your own, I don't recommend it. It's safer for people with heart failure to exercise in a place where they're monitored and supported during training. That's where cardiac rehabilitation can help.

What is cardiac rehabilitation?

Cardiac rehabilitation is a supervised program that helps you do more and feel better while you're doing it. It helps condition your body to work harder, so that you can do tasks, chores, and activities with far fewer symptoms. It may also make it less likely that you'll go to the hospital. It can also help you live longer.

The core of this program is exercise-based therapy. That's typically aerobic exercise, with some resistance or strength training. Often flexibility and balance is part of it, too. Cardiac rehab also covers nutrition and diet, and it offers education about the heart failure disease process and treatment.

One of the key things is that it's individualized. The difference between taking part in a cardiac rehab program and doing a Zumba or spin class at your local gym is that the exercise program is tailored to you. The other key feature is that it is supervised and directed by knowledgeable health care providers.

First, you go through an evaluation to check your abilities and limitations. Then the staff creates an individualized program, with some input from you.

A health team will supervise your program, including a doctor, nurses, and exercise physiologists, with some help from dietitians and psychologists or counselors. The staff will monitor your symptoms and vital signs like your blood pressure, EKG, and blood oxygen levels to make sure you're exercising safely.

Your cardiologist or primary care doctor should also be involved. You'll need to get an order from one of your doctors to take part in a cardiac rehab program, and they may monitor your progress while you're in it.

What types of exercise are best for people with heart failure?

Aerobic exercise is the foundation of physical activity for heart failure. That includes any kind of exercise that gets your heart pumping and makes your body need more oxygen. It generally involves using large muscle groups like your upper arms and legs.

Swimming, walking, or riding a bicycle all count as aerobic exercise. These are good additions to your cardiac rehab sessions, and you can continue them after you finish your program. Do whatever type you like best, so that you know you'll stick with it over the long term.

Other types of exercise can be beneficial, too, including strength training. Yoga and tai chi help with balance and flexibility. They can also be very calming. 

How often should you exercise, and for how long?

To improve your cardiovascular health, you want to exercise for at least 20 minutes a day, 3 to 4 days a week. While more exercise may be better, there's probably not much benefit to going beyond 60 minutes a day. If you do want to spend an hour exercising, you can do aerobics for 45 minutes and strength training or flexibility exercises for 15 minutes.

People who are just starting out may only be able to exercise for 5 minutes at a time. That's fine. Do 5 minutes of exercise, rest, and then do another 5 minutes of exercise. Ultimately you can aim for the full 20 minutes.

Most cardiac rehab programs happen three times a week over several months, for about 36 sessions in total. Over that time, the intensity of the exercise goes up gradually, which is important for helping your heart work better. If you walked on a treadmill for the same amount of time and at the same setting for years, you'd never get more fit.

Who shouldn't exercise?

If you can barely get out of bed or walk around the room without the help of a walker, you're not a good candidate for exercise or cardiac rehabilitation. That doesn't mean you won't ever be able to exercise. You can do physical therapy for a few weeks to improve your balance, strength, and walking ability. Once you feel stronger, then you can enroll in cardiac rehab.

What symptoms should make me stop exercising?

If you feel tired or short of breath at an unusually low level of exercise, that should be a red flag. For example, if you can normally exercise for 10 minutes, and now you're getting short of breath after 2 minutes, tell your doctor or exercise physiologist.

More potentially dangerous symptoms are things like lightheadedness or dizziness, chest pressure or pain, and an irregular heart rate. A cardiovascular rehab program should monitor for those kinds of symptoms. If the staff checks your blood pressure, heart rate, and oxygen level and finds that your measurements are OK, you should be able to continue exercising.

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