Oxygen debt describes a situation the body encounters, usually during or after vigorous exercise, that creates a short supply of oxygen to many bodily systems. Under normal conditions, the body receives a sufficient supply of oxygen to complete automatic tasks involving the muscles, tissues, lungs and bodily fluids. When a vigorous exercise routine is encountered, certain systems must work harder to supply the body with oxygen, therefore using more oxygen than is readily available. This is what causes you to be short of breath or leaves you gasping for air after a brisk run, workout routine or other short bursts of exercise.
Variances in Oxygen Debt
The recovery of oxygen to offset the debt is responsible for several factors. Most of the recovery processes last a few minutes to a few hours, but some can take several days. Changes in diet, or additional muscle training may alleviate some of the oxygen debt leading to less shortness of breath while exercising. Body weight is a factor as well. Maximum oxygen uptake is determined by sex, age and weight, meaning the amount of oxygen required to replenish the oxygen debt will vary. This may be the reason older people and those who have problems with obesity have a more difficult time with physical exercise.
The Process of Recovery
When the muscles experience rapid movement and muscle pressure, such as with exercise, the increase in speed by which normal events take place quickly uses up this steady flow of oxygen. A small portion is used to re-oxygenate myoglobin, which is a pigment in the muscles that acts as a small storage facility for oxygen. Most of the oxygen supply, however, involves the conversion or breakdown of lactic acid.
Lactic Acid and Oxygen Debt
One of the main jobs of the body after vigorous exercise is to take care of the excess lactic acid that has been produced. Lactic acid is a result of muscular use without the presence of oxygen, and it must be either converted into glycogen and glucose for use by the body, or broken down into carbon dioxide and water. Lactic acid is formed to maintain energy levels that the body needs to continue activity. It comes from a temporary conversion of pyruvate, and breaks down glucose for faster energy production.
There are other systems in the body that will need to recover from oxygen debt. ATP, or adenosine triphosphate, is one of the components necessary for conversion of pyruvate into lactic acid. Stores of ATP need to be replenished with oxygen, as does the supply of glycogen. Glycogen is a molecule that serves as a secondary and long-term storage of energy, and one of its uses is for situations just like the one of sudden and vigorous exercise. As the storage depletes, glycogen is made on the fly, and will be reproduced and stored over a period of 2 hours to a few days, depending upon the level of oxygen debt.