THE EXERCISE PRESCRIPTIONTHE EXERCISE PRESCRIPTION
Prescribing exercise for patients with heart disease follows the same principles as those used for the apparently healthy population. It is important to define the type of activity to be performed, as well as the intensity, duration and frequency of exercise.
Types of exercise.
The types of exercise that improve aerobic capacity are those involving large muscle groups in repetitive motions, with low resistance (e.g., walking, dancing, cycling, swimming and cross country skiing).
Intensity.
The recommended intensity of exercise (target heart rate) is 65% to 85% of the maximal heart rate. The maximal heart rate must be determined from a symptom-limited exercise test, usually done on a treadmill or stationary cycle. When there is evidence of ischemia during the exercise test, the maximum heart rate for training should be 10 beats per minute lower than the heart rate observed at the onset of ischemia. Training within the target heart rate will improve the patient's effort tolerance. Training at higher levels offers little further benefit and increases the risk of both cardiac and musculoskeletal complications; therefore, it is extremely important that cardiac patients do not exceed the pre scribed intensity of exercise. The radial or carotid pulse can be used to verify the heart rate during or immediately following activity. For patients receiving medications which can lower the heart rate (beta-blockers and some calcium channel blockers), the target heart rate is determined from the exercise test while taking their usual medication. If there is a change in these medications, a repeat exercise test is necessary to re-evaluate the target heart rate. -
The use of a scale of perceived exertion is helpful in teaching patients how to regulate exercise intensity. During the exercise test, the patient is shown a numerical scale with descriptive markers of perceived effort ranging from very, very light to very, very hard (Table 1). At every minute of exercise, the patient describes the rate of perceived exertion (RPE). Once the target heart rate is calculated, the RPE corresponding to the tar get heart rate is noted and can be used to guide exercise intensity during physical activities. This provides a method of continuous feedback and is particularly helpful in sports which make it difficult to monitor the heart rate (e.g., swimming, cycling or winter activities).
Duration.
The duration of exercise should be between 20 and 40 minutes. In order to limit injury and postexercise hypotension, exercise sessions should be pre ceded by a warm-up period (of about 10 minutes) and followed by a cool-down period of about 10 minutes.
Frequency.
The frequency of exercise should be between three and five sessions per week. For patients with reduced functional capacity, more frequent activity sessions of short duration and low intensity can be advised. An individualized approach with attention to the patient's interests is important in maintaining compliance with the exercise program. Walking is an example of a low intensity activity that is safe and enjoyable, and is more likely to be continued long term than some higher intensity activities.