Aerobic Workout Components
An aerobic workout should follow a consistent pattern to optimize safety as well as enjoyment. You should begin with a warm-up, which is followed by the main part of the workout, called the endurance conditioning phase. The workout is then wrapped up with a cool-down. See figure 6.1 for an overview of an aerobic exercise session.
A warm-up that consists of a minimum of five to ten minutes of low- to moderate-level activity is essential.1 The intent of the warm-up is to literally increase the temperature of the muscles, thus preparing the body for the demands of the endurance conditioning phase, or main focus, of the workout. A warm-up prepares your heart, lungs, and muscles for the endurance conditioning phase of your aerobic training session. Think of the warm-up as an on-ramp to a freeway. The on-ramp gives you time to bring your vehicle up to the speed of traffic to avoid an accident. The faster the traffic is, the longer the on-ramp should be. In the same way, your warm-up should be longer if the intensity of the conditioning phase is high.
Warm-up activities may include some light calisthenics or lower-level activities similar to what you will be including in the conditioning phase. For example, if your program includes brisk walking for the conditioning phase, then the warm-up could include slower-paced walking. If the conditioning phase includes a more intense activity such as running, then jogging would be appropriate in the warm-up. The point is to gradually increase the intensity from resting levels to the intensity you plan for the conditioning phase.
Endurance Conditioning Phase
To continue with the freeway analogy, the endurance conditioning phase is the freeway itself—the main focus of your journey. The conditioning phase for aerobic activity is guided by the FITT principle, which stands for frequency, intensity, time, and type.2 Frequency refers to the number of days per week in which you set aside time for exercise. Intensity reflects how hard you are working when exercising.
Time simply refers to the duration you are active, on a daily or weekly basis. And, type, or exercise mode, focuses on activities that involve large-muscle groups to improve cardiorespiratory fitness.
Although FITT nicely summarizes the conditioning phase, some fitness professionals like FITTE better—the E stands for enjoyment! All the recommendations and information in the world will mean little if you do not stick with your exercise program. Understanding the benefits of an exercise program (as outlined in chapter 1) will help you adhere to it, but considering the time commitment you are making, you should also be sure you are having some fun. Suggestions for keeping exercise enjoyable are found later in this chapter. First, consider the nuts and bolts of an aerobic exercise program.
The recommended frequency of aerobic exercise is between three and five days per week. How many days you exercise will depend on your goals and the intensity that is most appropriate for you. Although as few as a couple of days per week of activity can provide benefits, regular physical activity provides more benefits and has a lower risk of musculoskeletal injury than sporadic activity.1, 3 You will need as few as three days per week if you are engaging in vigorous activity, but at least five days per week is recommended if you plan on moderate-intensity activity. For example, if you enjoy running (a vigorous activity), three days per week will provide you with health and fitness benefits. However, if you plan on a walking program (a moderate-intensity activity), then at least five days per week would be better. If you enjoy mixing types and intensities of activity,3 then a weekly combination of three to five days of moderate and vigorous activity is recommended.1 For example, you may walk a couple days per week and jog on another couple days. This would be considered at two days per week of moderate activity (i.e., walking) and two days per week of vigorous activity (i.e., jogging), allowing you to meet the recommended amount of physical activity.
As the intensity of activity increases, so do the potential health benefits. To promote health and fitness benefits, your exercise must place some stress on your cardio-respiratory system. In other words, you should notice an increase in your heart rate and breathing. When speaking of intensity, fitness professionals generally use the terms moderate and vigorous.3 For a quick picture, consider moderate-intensity activity to be equivalent to brisk walking and vigorous-intensity activity to be equivalent to jogging or running.3
A variety of simple methods are available to help you quantify the intensity of your exercise bout. One method is to monitor your perceived level of effort. Although this is subjective (i.e., you determine how easy or hard you are exercising), a numerical scale can help guide you to appropriate levels of activity. The U.S. Department of Health and Human Services’ Physical Activity Guidelines for Americans suggests a scale of 0 to 10. Sitting at rest is 0, and your highest effort level possible is 10.3 Moderate-intensity activity is a 5 or 6 on this effort scale. Vigorous-intensity activity is at a level of 7 or 8. This method allows you to individualize your exercise based on your current level of cardiorespiratory fitness.3 For an example of applying this scale, see figure 6.2.
Another method, called the talk test, can also be used to establish exercise intensity at a moderate level. If you are working at an intensity that increases breathing rate but still allows you to speak without gasping for breath between words, you are likely exercising at a moderate intensity. The goal would be to exercise to the point at which speech would start to become more difficult. The Physical Activity Guidelines for Americans suggests that moderate-intensity activity allows you to talk but not to sing, whereas more vigorous activity results in an inability to say more than a few words without pausing for a breath.3
Heart rate monitoring can also be helpful for determining your intensity level, although it is a bit more technical than the subjective measures of effort level and the talk test. The maximal heart rate for adults can be estimated by multiplying your age in years by 0.67 and then subtracting that product from 206.9 (numbers in bold are constants, or set values, in the following equation).
206.9 – ( age in years × 0.67) = estimated maximal heart rate
You will not be exercising at maximal heart rate, but rather, at a percentage of that value; the percentage will depend on your fitness level (consider the values in table 6.1 as a starting point).2 Multiply your estimated maximal heart rate by the activity factor from table 6.1 to determine your target heart rate.
estimated maximal heart rate × activity factor
= target exercise heart rate in beats per minute
Note that your heart rate can also be influenced by environmental conditions (e.g., hot, humid environments) as well as medications (e.g., beta-blockers used for migraines and heart disease can lower heart rate). The calculated value should be used in conjunction with perceived exertion or the talk test. You can adjust your workload up or down depending on your perception of effort on a given day. A description of how to assess your heart rate is found on page 24 in chapter 2. Recall that during exercise you can count the number of beats in 15 seconds and then multiply that number by 4 to determine your beats per minute.
Recognize, too, that you can vary your intensity during the conditioning phase. Athletes often use interval training, which includes some time at higher intensity followed by lower-intensity exercise. This provides a unique stress on the body that translates into improved aerobic fitness. This principle can be used for general exercise programs as well. For example, if you are just beginning to exercise, you could include a few minutes at a faster walking pace within your conditioning phase. Alternating between lower and higher intensity provides variety as well as a stimulus to improve your aerobic capacity, no matter your current level of fitness.
Read more about ACSM’s Complete Guide to Fitness & Health, edit by Barbara A. Bushman, PhD, FASCM.