A quick measure of aerobicis how out of breath you feel when you walk up a flight of stairs. Aerobic fitness refers to the efficiency with which the body takes in oxygen and transports and utilizes it. If you enjoy a high level of aerobic fitness, your heart will beat slowly and strongly, pumping sufficient blood around the body, even when you exert yourself. In physiological terms, ‘aerobic’ means ‘in the presence of oxygen’. The energy that you burn up comes from the oxidation of fat. This process produces a chemical compound known as adenosine triphosphate (ATP), which fuels the contractions of muscles.
Aerobically fit people can jog, run, walk and swim for longer periods with fewer signs of fatigue and breathlessness than people who are not. Aerobic fitness is therefore defined by how long you can continue a rhythmic activity, such as jogging, which makes you breathless. It is is also known as stamina, endurance or cardio-respiratory fitness because the length of time you can keep going depends on your heart, lungs and circulatory system. Aerobic fitness is improved by aerobic exercise – any continuous rhythmic activity that uses large muscle groups and causes breathlessness. Aerobic exercise, sometimes called cardio-work or fat-burning exercise, improves aerobic fitness by strengthening the heart and lungs, clearing the arteries and bringing down high blood pressure and levels of cholesterol.
During aerobic exercise, the adrenal glands, which are situated on top of the kidneys, release the hormone adrenalin. Adrenalin makes the heart beat faster and more forcefully, enabling the body to cope more efficiently with physical activity and exertion. Adrenalin also widens the airways to facilitate breathing and narrows the blood vessels in the intestines and skin so that blood is directed to the muscles where it is needed most.
The various forms of aerobic exercise are discussed in terms of impact – low, medium and high. This refers to the impact on the joints when exercising – and walking are low-impact activities, whereas jogging and running are high impact.
Benefits of aerobic exercise
One of the main benefits of aerobic fitness is that you can easily sustain day-to-day activities without becoming breathless or fatigued. In practical terms, this means that you can walk and run without feeling overly tired and you can compete at an optimum level in sports such asor football.
Because aerobic exercise burns the body’s fat reserves as fuel, it can aidif it is combined with a healthy, low-fat diet. The longer the exercise session, the greater the amount of fat burned. Aerobic exercise also builds bone mass, improves muscle strength and increases energy levels.
The long-term health benefits of aerobic exercise include the prevention of hyper-tension and cardiovascular disease and a reduced likelihood of diabetes in later life (late-onset diabetes is linked to obesity). Because weight-bearing aerobic exercise increases bone density, it may also help to prevent osteoporosis.