The cardiovascular system determines the supply of oxygen-rich blood to muscles. The respiratory system also plays an essential role in athletic performance as oxygen levels will influence how hard a muscle can work and for how long.
The oxygen uptake (VO2) of an athlete is the amount of oxygen which the body uses in a minute. It should not be confused with the ventilation rate, which is the total amount of air per minute passing in and out of the lungs. Oxygen uptake is believed to be one of the best indicators of an athlete's overall fitness. Most training works to improve the athlete's ability to move oxygen into the cells and improve the ability of the cells to use the oxygen.
The standard measure of oxygen uptake is:
|VO²||= millilitres of oxygen used per kilogram of body weight per minute
Like many components of fitness, VO² max has a genetic component where an individual is limited by their inherited characteristics. It is also known that VO2 max can be increased through training by increasing training volume and intensity. The less fit an individual is, the more they can increase their VO2 max (sometimes by up to 20 percent through proper training). Fit athletes have a harder time increasing their VO² max, as they are often close to their genetic potential.
The link below will further assist your understanding of oxygen uptake.
Lung capacity is the amount of air that can move in and out of the lungs during a breath. The basic principle is the greater the volume of air that can be inhaled and exhaled during exercise, the greater the amount of oxygen that can be absorbed into the blood stream. More oxygen leads to improved performance during aerobic work.
As a result of training a number of adaptations occur within the lungs, due to the increased efficiency of the lungs, rather than changes in the size of the lungs. The strength and endurance of the lung tissue and surrounding muscles increases, a greater volume of air can be inhaled and exhaled as well as faster breathing (ventilation). Training also increases the number of capillaries in the lungs, allowing more oxygen to be absorbed with each breath taken.
For more information on lung capacity view the following link. http://www.upgradeyourbody.com/articles/fitness/how-to-increase-lung-capacity.html