The definition of cardiovascular endurance simply put is the body’s ability to continue exertion while getting energy from the aerobic system used to supply the body with energy. This is the system that kicks in third after the phosphogen and the glycogen lactic acid system, and so the one that supplies energy to the human circulatory system and the muscles over extended periods.
Cardiovascular endurance is most useful for long distance sports; for marathon training, long distance running, jogging and swimming, however it will also be useful for everyone else and a lack of it will lead to individuals becoming quickly tired and out of breath. In a marathon, the person who comes first (while allowing for injury or general poor technique) will generally be the person with the best cardiovascular fitness. To fully understand the definition of cardiovascular endurance, it’s important to understand how the body utilises energy to power its muscles.
Essentially, all energy in the body of every living organisms comes from a substance called ‘ATP’, the ‘energy currency’ of life on Earth. ATP stands for ‘Andenosine Triphosphate’, a name that describes the chemical composition of the substance. ATP you see is an adenine nucleotide made up of three phosphates attached by powerful high-energy bonds. When these bonds are broken they release energy, which the body then utilises to power the muscles etc and which forms the basis of the posphogen system, powering the body for 3 seconds using the ATP stored in the muscles.
As well as giving off energy however, the phosphogen system also has two other by-products, ADP and AMP, which stands for Andenosine Diphosphate and Andenosine Monophosphate respectively. These are similar to ATP, except in that they describe adenine nucleotides with just two or one posphates respectively. In other words, they are the two parts of the ATP once the bonds are broken. Fortunately however the body also stores and produces another substance called Creatine in the Kidneys. Creatine is meanwhile used by the body to recombine ADP and AMP to make new ATP that can be once again used by the body. This then supplies an additional 8-10 seconds of energy on top of the initial 3 seconds and can be used by the body for extended explosive exercise. Using these methods combined then the body can utilise the phosphogen system for energy for a full 13.5 seconds, making it the best type of energy for explosive movements, such as weight lifting, 100 metre sprinting or jumping. Some athletes take a creatine supplement with the belief that it will increase that 8-10 seconds. The definition of cardiovascular endurance does not encompass this system of energy release, as the ATP and creatine is readily accessible by the body, thus cardiovascular endurance is not necessary for sprinting.
Once the body has used up its supply of ATP and creatine, it will move on to a secondary method for energy – the glycogen lactic acid system. Here the body falls back on another substance found in the muscles, namely glycogen. As a form of carbohydrate this too can be broken down into ATP and so used for energy supplying an addition 1.5 minutes, though this system is slower than the phosphogen system and also results in another by-product named ‘lactic acid’ which can cause the muscles to feel stiff and uncomfortable. It’s lactic acid that creates the feeling of the ‘burn’ sought after by bodybuilders and runners while training, but which can also make it difficult to continue performing when it builds up. This is why the glycogen lactic acid system is the secondary system used.
It is only after these two systems however that the aerobic system kicks in. The definition of cardiovascular endurance then is the ability to continue exertion following the initial 1.43.5 minutes. At this point the muscle must find its energy from other areas around the body and then transport it to the areas it is needed and this is done via the bloodstream. Here the body uses oxygen to break down energy stored in the mitochondria around the body in the form of foods – either fat or protein. In this way the body begins to ‘burn’ its own fuel supplies, stored as fat and muscle, in order to find energy to continue exertion. This energy, in the form of ATP of course, is transported via the blood to the muscles resulting in the feeling of being ‘pumped’. This system can supply the body with up to two hours of additional performance, though precisely how long will depend on the fitness of the individual (that being the definition of cardiovascular endurance). While this system is fairly slow, and can eventually begin to damage muscle tissue, at the same time it produces no by products other than harmless carbon dioxide and water. It is the aerobic system that the body relies on for long distance running such as that needed for a marathon.
The aerobic system relies on many other organs and systems being in place then, and in fact another definition of cardiovascular fitness could be to have a strong heart, high VO2 max, lung capacity, breath control and a healthy circulatory system. It is through these bodily systems that we are able to extract the oxygen from the air and transport it through the blood to the relevant areas. The term VO2 max refers most specifically to the body’s maximum rate at which it can draw oxygen from the air, and can be trained through cardiovascular exercise and more specifically by training where the air is thinner – in the cold or at high altitudes.
Obviously a strong heart is crucial for cardiovascular fitness as it’s what will pump the blood round the muscles to the mitochondria and the muscles. This will be transported through the veins and arteries that make up the ‘human circulatory system’. A healthy circulatory system can be maintained through consumption of fibre, which travels through the veins and arteries to unclog arterial plaque, and by eating a diet low in carbohydrates and saturated fats.
Between these elements then is found an in-depth definition of cardiovascular endurance. Through understanding the exact process that goes into cardiovascular fitness you can train each aspect separately to improve every aspect of your performance.