It’s All About the Oxygen
By definition, aerobic fitness refers to your ability to transport and utilize oxygen, measured by VO2 max, the maximal amount of oxygen you can use during intense exercise. Exercise scientist Len Kravitz, PhD of the University of New Mexico explains that VO2 max is influenced by central and peripheral components. The central component involves the ability of your lungs, heart and vascular system to deliver oxygen to your muscles via your blood stream. The peripheral component involves the ability of your muscle cells to extract oxygen from your blood and use it to make ATP, the fundamental unit of energy. VO2 max values are lower in women, and decrease incrementally with age.
Priming the Pump
Your heart and lungs play a central role in aerobic fitness, with your heart being the prime limiting factor. While your lungs must function efficiently in order to transfer oxygen from the atmosphere to your bloodstream, they take a backseat to your heart, which must contract forcefully to eject oxygenated blood into your system to reach your cells, accounting for 70 to 85 percent of VO2 max. According to Kravitz, aerobic exercise training increases your total blood volume, heart muscle size and contractile, resulting in a greater volume of blood being ejected per each heart beat. Increased stroke volume means your heart does not have to beat as frequently at rest, resulting in a lower resting heart rate.
Max Extraction
Regardless of how efficiently your heart pumps, aerobic fitness is also dependent on the ability of your muscle cells to extract oxygen from your blood and use it to make energy. Aerobic energy is produced in the mitochondria of your muscle cells, using carbohydrates and fats for fuel. Mitochondria are microscopic organelles that function as energy factories for aerobic metabolism. In response to repeated bouts of aerobic exercise, the density and number of mitochondria increases. High-intensity exercise that challenges your aerobic limit has a more profound effect on mitochondria adaptations and oxygen extraction than low- to moderate-intensity activity, according to Olympic coach David Joyce of “Peak Performance.” During high-intensity exercise, you exceed your body’s ability to produce aerobic energy, forcing it to tap into anaerobic pathways. However, anaerobic energy can only be sustained for a very limited time, usually less than two minutes. Perpetually exceeding your anaerobic threshold causes your muscles to adapt to perform aerobically at higher intensities.
Measuring Up
While VO2 max is the ultimate measurement of aerobic fitness, it relies on a complex and invasive evaluation in a laboratory setting, conducted by trained technicians. According to “ACSM’s Complete Guide to Fitness and Health,” other methods may be used to measure your aerobic fitness. One way is to monitor your heart rate during maximal intensity exercise and translate it as a percent of your maximal heart rate, which you can calculate using the equation: 206.9 – (age in years × 0.67) = estimated maximal heart rate. The more fit you are, the higher your percent of max heart rate during exercise. Aerobic fitness classifications ranging from low to excellent are reflected by values of 60 to 90 percent of max heart rate, respectively.
Aerobic Endurance Fitness Tests
Aerobic Endurance
Aerobic endurance, or cardiovascular endurance, is the ability to continuously perform rhythmic large muscle contractions for an extended period of time. Activities like walking, running, cycling, and swimming are all considered aerobic in nature. In order to perform optimally, your muscles require an uninterrupted supply of oxygen during aerobic exercise to meet the demands for energy in the working muscles. According to the American College of Sports Medicine, fitness assessments are useful for developing exercise training programs, and for screening for risk of heart disease and other metabolic diseases.
Measurement of Aerobic Endurance
According to the IDEA Health and Fitness Association, the most important measure of aerobic fitness is maximal oxygen consumption, or VO2 Max. VO2 Max is a measure of how much blood is pumped per minute and the amount of oxygen that is extracted by the working muscles during that minute. (reference 3) Fitness test results can be used to measure baseline fitness at the onset of an exercise program, to design programs appropriate for the individual, and to measure improvements realized from fitness training.
Field Tests
Field tests for aerobic endurance are often conducted by athletic coaches and fitness professionals in a non-clinical setting. They can be performed on groups of athletes or individuals simultaneously, and require minimal equipment. Examples of field tests include the YMCA three-minute step test, the Balke 15-minute run, the Cooper 12-minute run, and the Rockport walking test. The step test requires a 12-inch platform, a stop watch and a metronome. The Cooper, Balke and Rockport tests require a 400m track and a stopwatch.
Clinical Tests
In a clinical setting, aerobic endurance tests are performed by trained technicians or medical personnel, and are often scheduled through your health care provider. The test is conducted on a treadmill or cycle ergometer, and uses a 12-lead electrocardiogram, or ECG, to monitor and assess your heart function. The test may also entail special apparatus to measure oxygen consumption at the mouth. Clinical tests can be expensive, invasive and time-consuming, but the results are more exacting than a field test. If you are at risk for heart disease or have suffered a coronary event, a clinical test is recommended prior to beginning an aerobic fitness program.
List of Aerobic Workouts
Walking
Walking is a convenient, low-impact form of aerobic exercise. You can increase the intensity of a walking workout by walking up hills and increasing the pace and stride length. In a study published in the New England Journal of Medicine, researchers looked at how walking affects mortality rates — they studied the benefits of walking in a group of over 700 men. Participants’ daily walking mileage was recorded for two years and then a follow-up study was performed on this same group of men 12 years later. The mortality rate of the men who walked less than 1 mile daily was twice the rate of those who walked over 2 miles.
Running
Running is a high-intensity aerobic workout. It can be performed indoors on a treadmill, or outdoors in a park, on the sidewalk, on trails or on an outdoor running track. Running shoes and running clothes are the only equipment required. Running can burn between 584 and 1,472 calories an hour, depending on your weight and running speed. Some people may also be sensitive to certain weather conditions.
Aerobic Dance Classes
Aerobic dance classes became popular in the 1970s. These classes feature choreographed aerobic activity performed to music. Some classes involve stepping up and down on an 8- to 12-inch platform. High-impact classes — which involve jumping, hopping and running activities — will usually burn more calories than low-impact aerobics, but in some cases, they have a greater potential for injury. The calories burned in aerobic dance classes will vary according to the intensity of the movements. Overly complex choreography might impede the participants’ ability to follow the movements, resulting in a less-intense workout.
Winter Sports
Many people claim that they gain weight during the winter. In some cases, this may be due to decreased activity, but a condition known as SAD, or seasonal affective disorder, may contribute to the problem. While the condition is sometimes treated with light therapy, participating in a winter sport might alleviate the symptoms. Cross-country skiing and snowshoeing will burn the most calories, because they do not involve a chairlift. You can get some aerobic benefits from downhill skiing and snowboarding by choosing longer trails.
Cycling
Whether you cycle indoors on a stationary bike or outdoors, this type of activity is low-impact. Outdoor cycling has an added benefit: it enables you to travel considerable distances and explore interesting territory. According to the Centers for Disease Control and Prevention, cycling on level terrain or on a stationary bike, at 5 to 9 mph, is a moderate-intensity aerobic activity. For a higher intensity workout, try mountain biking, bike racing or cycling more than 10 mph.
Indoor Aerobic Exericse Equipment
Most fitness centers have a variety of cardiovascular machines, which may include ellipticals, stationary bicycles, treadmills and rowing machines. Some of these machines have mechanisms that allow you to work your upper- and lower-body simultaneously. Others can be intensified by increasing the incline. Personalized video screens are a new trend in indoor aerobic exercise equipment. They allow you to do your workout while watching your favorite television shows.