How to Implement Physical Activity in Primary and Secondary Prevention
A Statement for Healthcare Professionals From the Task Force on Risk Reduction, American Heart Association
Substantial data exist on the benefits of physical activity in both primary and secondary prevention of cardiovascular disease. These data are well documented in American Heart Association position statements,1 2 the current Surgeon General’s report,3 and population studies.4 5 6 7 8
The purpose of this “how-to” statement is to delineate the fundamentals of implementation of physical activity in both primary and secondary prevention of cardiovascular disease. The recommendations and rationale of earlier scientific statements1 2 on exercise have been translated into practical suggestions that can be implemented in the physician’s office.
Physical activity in primary prevention should begin in the early school years and continue throughout an individual’s lifetime. Schools must specifically designate physical education programs with aerobic activities for children at early ages. Programs should include recreational sports such as running, dancing, swimming, and selected types of resistance exercises using free weights and/or specific equipment. There also should be support for an active lifestyle for children at home.
In the patient-visit setting, physicians and their staff should discuss physical activity and provide exercise prescriptions for patients and their families. In some instances, suggestions could be made about implementing physical activity recommendations at the worksite.
Intensity, duration, and frequency as well as mode and progression should be considered in all types of physical activity programs. As children and adolescents become adults and discontinue the athletic endeavors of school and college, primary prevention must include a plan for a lifetime of appropriate physical activity. Ideally this activity should be done for at least 30 to 60 minutes four to six times weekly1 or 30 minutes on most days of the week.3 The frequency, duration, and intensity of the activity should be individualized to personal satisfaction as well as mode and progression. Subjects may use individual end points of exercise such as breathlessness and/or a fatigue level considered “somewhat hard” to “hard” on the Borg perceived exertion scale.9 Standardized charts that designate heart rates may help by providing heart rate end points that can be measured immediately after exercise, but these are not necessary.10 Exercise should include aerobic activities such as bicycling (stationary or routine), walk-jog protocols, swimming, and other active recreational-leisure sports. Shoes and clothing appropriate for extremes of heat, cold, and humidity should be worn.
Resistive exercises using free weights or standard equipment should be done two to three times weekly. These exercises should include 8 to 10 exercise sets consisting of 10 to 15 repetitions per set (arms, shoulders, chest, trunk, back, hips, legs) performed at a moderate intensity. If free weights are used, 15 to 30 pounds are adequate. Resistive exercises tend to complement aerobic exercise in that some training effect is realized. However, development of muscle tone is more important, as is strengthening of body musculature as adults age over time.1
The long-term effect of any physical activity program is affected by compliance. In today’s mobile society, an exercise plan must include activities for business trips and vacations. Exercise facilities may not be convenient in such settings, which may mean “improvising.” For example, a “walk-jogger” should bring walking or running shoes and find a safe place to walk or run at a pace that approximates his or her usual activity level. Many hotels or motels have an exercise facility with track or treadmill, exercise cycle, and weights, enabling travelers or others who are away from their usual routine to maintain an exercise program.
Physical activity measured in total time or kilocalories per week is appropriate and may be achieved with various combinations of scheduling, such as 10 to 15 minutes in the morning and at noon and/or an afternoon/evening session. Many persons may schedule longer, less frequent periods of exercise. As intensity decreases, frequency and duration should increase and vice versa. The “dosage” or total calorie expenditure per week must be individualized.
Persons with influenza syndromes or respiratory illnesses should decrease or stop exercise until they have recovered. If the recovery time is greater than 2 to 3 weeks, activity should be resumed at a lower level to compensate for the slight loss of training level.
Various exercise testing measures of functional capacity are of interest but not necessary for primary prevention. Many athletically inclined persons like to have periodic oxygen consumption measurements to assess their level of training, but this is not routinely recommended. However, exercise testing should be done in those who are considered at high risk for cardiovascular disease (for example, those with hypertension or abnormal blood lipid levels).
A lifestyle of physical activity from childhood throughout the adult years fosters health and longevity.1 This improved state of health is enhanced by weight control, restricted intake of saturated fat and cholesterol, abstinence from cigarette smoking, and control of high blood pressure and glucose intolerance.
Walking is the recommended mode of activity unless the individual can attend supervised classes where other activities can be provided. Limited walking should begin and continue slowly with a gradual increase in duration until 5 to 10 minutes of continuous movement has been achieved. Active but nonresistive range of motion of upper extremities is also well tolerated early as long as the activities do not stress or impair healing of the sternal incision in persons who have had coronary bypass surgery.
The emphasis of exercise in the first 2 weeks after myocardial infarction or coronary bypass surgery should be on offsetting the effects of bed rest or former periods of inactivity. When the individual’s condition is stable, as measured by electrocardiography, vital signs, and symptomatic standards, he or she should begin to increase the activity. Although the prescribed activity is usually well tolerated and safe, certain precautions are recommended, such as awareness of chest discomfort, faintness, and dyspnea.
Initial activities should be supervised, and symptoms, rating of perceived exertion, heart rate, and blood pressure recorded. When safety and tolerance are documented, the activity can be performed without supervision.
A symptom-limited exercise test is often performed after the individual’s condition has stabilized (as early as 2 to 6 weeks after the coronary event). In secondary prevention such testing is essential in all subjects before beginning a physical activity program. If more studies such as echocardiography or angiography are not indicated, a regular conditioning program can be initiated with a careful prescription of activity based on results of the exercise test.
For conditioning purposes, large-muscle group activities should be performed for at least 20 to 30 minutes (preceded by warm-up and followed by cooldown) at least three to four times weekly. The exercise prescription should be based on the exercise test. Supervised group sessions are recommended initially to enhance the exercise educational process, ensure that the participant is tolerating the program, confirm progress, and provide medical supervision in high-risk situations.1 2 Unsupervised home programs are acceptable for persons at low risk who are motivated and who understand the basic principles of exercise training.
General Principles of Exercise Prescription in Secondary Prevention
Prescription in the Absence of Ischemia or Significant Arrhythmias (Low Risk)2
Exercise intensity should approximate 50% to 80% of maximal oxygen consumption (V̇o2max), as determined by an exercise test. If a test is not done initially, a measurement of 20 beats per minute (bpm) above resting heart rate is adequate until testing is performed.
The exercise-training heart rate should be designated as 50% to 75% of heart-rate reserve ([maximal heart rate−resting heart rate]×50% to 75%) plus resting heart rate. Activities can be prescribed according to the work intensity at which the training heart rate is achieved after 5 to 10 minutes at the same workload (steady state). This may be expressed as watts on an ergometer, speed on a treadmill, or metabolic equivalents (METs) (one MET equals 3.5 mL/kg per minute of oxygen consumed). If an individual cannot assess intensity, then heart-rate counting (manually or with a cardiotachometer) is especially useful. Heart-rate counters are widely available and generally accurate for low- to moderate-intensity exercise.
If an individual intends to walk on a level surface, activity can be prescribed as the treadmill step rate that generates the desirable heart rate. The step rate is the number of steps taken in 15 seconds while walking at the desired speed on the treadmill. Step rate can be easily counted since it requires less skill than counting heart rate. If this approach is used, individuals should be cautioned to avoid hills. Walking in shopping malls or gymnasiums allows subjects to avoid inclement weather and exercise on a flat surface. Exercise should be supervised for the first few sessions to ensure that instructions are understood and the activity is well tolerated.2
Individuals can also judge the intensity of exercise as the rating of perceived exertion, which can be equated with desirable heart rate during laboratory exercise and their activities. The original scale is a 15-grade category scale ranging from 6 to 20, with a verbal description at every odd number beginning at 7, or very, very light, and progressing to 19, or very, very hard.
The following rating of perceived exertion values should be followed: less than 12, perceived as fairly light (light intensity), 40% to 60% of maximal heart rate; 12 to 13 perceived as somewhat hard (moderate intensity), 60% to 75% of maximal heart rate; 14 to 16 perceived as hard (high intensity), 75% to 90% of maximal heart rate.
Activities can progress as tolerance is demonstrated. An appropriate initial intensity of training is 60% to 75% of maximal heart rate (moderate) or a rating of perceived exertion of 12 to 13. However, many individuals may need to begin at 40% to 60% of maximal heart rate (light). After safe activity levels have been established, duration is increased in 5-minute increments each week. Later, with increased strength and as heart-rate response to exercise decreases with conditioning, intensities can be increased, at a frequency of three to six times weekly. At this point limited resistive exercises can be added as described previously. These have proved both safe and effective in secondary prevention.2
Prescription in the Presence of Ischemia or Arrhythmias (Moderate to High Risk)2
An exercise test and medical supervision are essential for this type of prescription. The manifestations of arrhythmias or ischemia that require such precautions can vary but usually include ventricular tachycardia (≤3 to 4 beats), any arrhythmia that is symptomatic or causes hemodynamic instability, chest discomfort believed to be angina, ECG ST depression ≥2 mm, or a decrease in systolic blood pressure ≥20 mm Hg from baseline.
Exercise testing is performed in the usual fashion, but the conditioning work intensity is derived from the heart rate associated with the abnormality. If the exercise test continues to a high level of effort, the heart rate at 50% to 60% of maximum can be used if it falls at least 10 beats per minute below the abnormal level. Otherwise, the recommended peak training heart rate is 10 bpm less than that associated with the abnormality. It is desirable that these individuals have medically supervised cardiac rehabilitation and reevaluation to “restratify” them to a lower risk.2 Exercise testing should be repeated at least yearly.
As the population ages and more elderly subjects survive coronary events, increasing numbers will need appropriate physical activity. Most of these subjects will benefit initially from supervised exercise for a brief period. This is done primarily to introduce the subject to exercise (which he or she may not have done before) and to evaluate the subject for possible complications of exercise, such as arrhythmias, evidence of heart failure, anginal chest pain, or abnormal ECG ST segments. On the basis of the evaluation, the subject can be categorized as low risk or moderate to high risk, and appropriate cardiac rehabilitation precautions can be taken.2
Most subjects in secondary prevention can soon be restratified as low risk and can implement their exercise prescription at home or in a community program. In this setting the previously mentioned primary prevention guidelines apply as well. The intensity may be much less, and the frequency may be more with appropriate changes in duration. Interval exercise testing is recommended at least yearly, and coronary risk factor modification should be aggressive.11
In summary, implementation of physical activity strategies by physicians in both primary and secondary prevention should consider the dosing effect or expenditure of kilocalories over a unit of time, usually a week. The guidelines above should, if possible, ideally entail 5 to 6 hours of various physical activities weekly. The exercise routine must be individualized and should include both aerobic and resistance activities. The benefits of exercise will be enhanced with good to excellent compliance with exercise and appropriate lifestyle modifications.
“How to Implement Physical Activity in Primary and Secondary Prevention” was approved by the American Heart Association Science Advisory and Coordinating Committee in November 1996.
A single reprint is available by calling 800-242-8721 (US only) or writing the American Heart Association, Public Information, 7272 Greenville Avenue, Dallas, TX 75231-4596. Ask for reprint No. 71-0127.
- Copyright © 1997 by American Heart Association
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