While there are numerous methods for evaluating aerobic capacity, in most instances treadmill walking/running is appropriate for the majority of individuals. Normative data correlates time on the treadmill with aerobic fitness. V̇O2 is an index of the body’s efficiency at producing work. It is expressed in milliliters of oxygen consumed per minute, and adjusted for body weight in kilograms: ml/kg/min. There are many factors that can influence V̇O2max, e.g. heredity, training, age, gender, and body composition. Generally, V̇O2max declines with age (about 2% per year after age 30) and males typically have a greater oxygen consumption value than females. Nevertheless, the trend is that a higher V̇O2 max allows one to produce more energy, thereby performing more work. With this in mind, V̇O2 max is the "gold standard" measure of overall fitness.
Aerobic fitness is assessed by having the subject perform exercise at increased loads, for 12 to 15 minutes, while breathing into a mouthpiece which collects information on inspired and expired air. A treadmill, personal bike on a Computrainer, or a stationary bicycle are typically used. The test starts with an easy-moderate work load which is maintained for a 1-2 minutes. The load is increased gradually every 1-2 minutes until reaching the maximum level that the subject can tolerate and/or until physiological parameters such as heart rate, oxygen consumption, f... have hit a peak or plateau. This is done by increasing the cycling resistance or the speed and/or grade of the treadmill. The oxygen uptake, heart rate, speed and/or watts are measured at the ventilatory threshold and at maximal load, the latter would be the subject's V̇O2 max.
V̇O2 max values cannot be used in every day training, but follow-up V̇O2 tests can be used as a measure of progress. However, since heart rate, speed and/or power is typically measured during a V̇O2 max test, various heart rate, speed and/or power levels can be garnered from testing and then associated to appropriate training zones, which are then applied to everyday training. Other information such as V̇O2 economy (oxygen consumption values at a given heart rate or power output) can also be extracted from the data, compared to subsequent tests and against performance norms.
Training results in an increase in the efficiency of oxygen transport within the body. By lowering the resting heart rate (HR), and the HR at sub maximal loads, the heart pumps more blood with every heart beat. This, in addition to other physiological changes, increases the oxygen extraction capability. When an individual is tested before and after training while performing exercise at the same load, a lower HR is shown after training because more blood (thus, oxygen) is delivered in each heart beat. Such HR differences during exercise can be used to predict aerobic fitness. The % of increase in V̇O2 max is dependent on many variables and differs considerably from individual to individual, ranging from 5-30%. In general, individuals who are the least fit see the largest changes and individuals who are highly fit see the smallest changes.
Significant amounts of research and public health data indicate that low aerobic fitness levels are correlated with an increased risk of premature death from many causes but in particular from cardiovascular disease. Accordingly, higher aerobic fitness levels are associated with numerous health benefits e.g. longer lifespan, better quality of life, reduced risks for stroke, heart disease, diabetes and cancer, improved mood and self-esteem, and improved sleep patterns. To improve or maintain cardiovascular health an individual must engage in cardiovascular exercise (run, walk, swim, bike, etc...) at least 3 times per week. Currently, however, public health data indicates that only 22-25% of Americans exercise regularly enough to achieve these positive health benefits.
V̇O2 max is also a predictor of performance, although its correlation to athletic success in endurance sports is only 30-40%, with other factors such as sustainable lactate threshold, motivation, training, etc... also playing a role. In general, however the higher a V̇O2 max the more potential for a successful performance in an aerobic endurance event.
Aerobic exercise provides cardiovascular conditioning. The term aerobic actually means "with oxygen," which means that breathing controls the amount of oxygen that can make it to the muscles to help them burn fuel and move.
Benefits of aerobic exercise
- Improves cardiovascular conditioning.
- Decreases risk of heart disease.
- Lowers blood pressure.
- Increases HDL or "good" cholesterol.
- Helps to better control blood sugar.
- Assists in weight management and/or weight loss.
- Improves lung function.
- Decreases resting heart rate.
Exercise safety
It is recommended that you talk with your physician before you start an exercise program. Ask what, if any, limitations you may have. People who suffer from diabetes, hypertension, heart disease, arthritis, pulmonary conditions, or other health conditions may need additional safety guidelines for exercise.
Note: If you develop symptoms during exercise including, but not limited to, unusual shortness of breath; tightness in the chest; chest, shoulder, or jaw pain; lightheadedness; dizziness; confusion; or joint pain, you should stop exercising immediately and contact your physician.
What are some examples of aerobic exercise?
Lower impact aerobic exercise includes:
- Swimming.
- Cycling.
- Using an elliptical trainer.
- Walking.
- Rowing.
- Using an upper body ergometer (a piece of equipment that provides a cardiovascular workout that targets the upper body only).
Higher impact aerobic exercise includes:
- Running.
- Jumping rope.
- Performing high impact routines or step aerobics.
How often and for how long should I do these exercises?
The American Heart Association recommends that everyone reach a minimum of 30 minutes of some form of cardiovascular exercise 5 to 7 days per week. This can be broken up into 10-minute time periods. This means that taking 3 walks of 10 minutes each would let you reach the recommended minimum guideline for reducing the risk of heart disease, diabetes, hypertension, and high cholesterol. You would also burn the same number of calories as you would if you walked for the full 30 minutes at 1 time.
The American College of Sports Medicine recommends a minimum of 3 sessions of 30 minutes of the total should be made up of moderate to vigorous exercise to improve cardio-respiratory fitness and help manage weight.
It is appropriate to do aerobic exercise every day. There is no need to rest in between sessions unless you are at an extreme level of training, such as preparing for a marathon, or if you experience reoccurring joint pain. If joint pain is a limiting factor, it would be appropriate to alternate less painful exercises with those that may cause joint pain or discontinue the painful exercise altogether.
Explanation of intensity
The intensity is determined by how hard you are working. The intensity of the exercise is determined by what your goals are, what limitations you have, and your current fitness level.
Heart rate and exercise
Your heart rate increases in direct correlation with the intensity of the exercise. Heart rate levels can vary significantly from one person to another based on fitness level, genetics, environment, and exercise tolerance. If you wish to train based on heart rate, contact your health care provider to determine what the appropriate range is for you. Some medications, most often blood pressure drugs, control heart rate, making it impossible to determine exercise intensity in this way. Ask your physician to determine if you are on any of these medications.
Monitoring intensity in other ways
How can you know if you are working at the right intensity? Using an RPE (Rate of Perceived Exertion) chart can help you to determine the appropriate intensity. The scale uses a 1 to 10 rating system. One is very light, such as walking to the refrigerator for a glass of milk. Ten would be a very significant level, representing maximal exercise. Ten would be indicative of not being able to take another step without fear of collapse. It is not recommended for anyone to work at a rate of 10 without strict supervision by a healthcare provider. Moderate intensity is the level of exercise that is most recommended, and can be determined by a rating between a 3 and a 5.
Warming up and cooling down
Every session of aerobic exercise should include a warm-up and cool-down. The warm-up period should not include static stretching, but should instead be a gradual increase in pace and intensity of the exercise. This allows the body to increase blood flow to the muscles and decreases the likelihood of a muscle or joint injury. The warm-up should last between 5 and 10 minutes. The cool-down session should last a similar amount of time as the warm-up, with the pace gradually decreasing. Stretching exercises would be appropriate after aerobic exercise.
Progression of aerobic exercise
Progression to higher intensities of exercise should be based on individual exercise tolerance. There are 3 methods for challenging aerobic fitness:
- Increase speed.
- Increase the resistance.
- Increase the duration.
Any of these methods, or a combination of these methods, will improve aerobic fitness. Increasing intensity should be done very gradually. You should challenge yourself for only a few minutes at a time.