Acclimatization and our body’s adjustments to temperature and pressure changes in high altitudes explains the response of the body to environmental changes in certain situations. However, the body also responds and adjusts to oxygen demands, metabolic rates, ATP and other changes during an exercise such as a sprint race. Below is a list of what happens to an athlete during a sprint race.
- Before and during the early stages of a sprint race, adrenaline is secreted from the adrenal glands into the blood stream which is as a result of the impulses received from the cerebral cortex of the brain. This adrenal secretion to the blood stream leads to
(i) an increase in cardiac frequency
(ii) a general constriction of the arterioles except for those serving vital organs like the heart, brain and lungs.
(iii) and a contraction of the spleen, which is the body’s main blood reservoir.
- During the sprint, the metabolic rate of the body increases. This increase is caused by the shortage of ATP(adenosine triphosphate) that inevitably results from muscular exertion. A decrease in the amount of ATP activates an enzyme which initiates the further phosphorylation of sugar which is a perfect example of a negative feedback mechanism.
- The increased metabolic rate during the sprint results in carbon(IV) oxide building up in the muscle tissues, which causes local dilation of the arterioles, leading to an increased blood flow through the muscles. It has been discovered that the increase in body temperature during the sprint leaves the tissues more sensitive to carbon(IV) oxide, thereby accentuating the mechanism.
- Local accumulation of carbon(IV) oxide in the muscles during an exercise is quickly followed by a general rise in the concentration of carbon(IV) oxide throughout the circulatory system. This, alongside with a decrease in oxygen concentration, stimulates the respiratory and cardio-vascular centres leading to
(i) Increased ventilation rate
(ii) Increased cardiac frequency, and
(iii) Constriction of arterioles
All the above listed events results in a rise in arteriole pressure, and also leads to an increased flow of blood through the active muscles.
- The increased arteriole pressure results in the stimulation of stretch receptors in the carotid sinuses. This phenomenon results in a decrease in cardiac frequency which will tend to decrease the speed of the circulation. This, together with the dilation of the muscle arterioles, safeguards the body from developing too high a blood pressure.
- During the sprint race, the metabolic rate of the active muscles increases greatly and the demand for oxygen rises accordingly. Despite the mechanisms that have been listed above, insufficient oxygen is delivered to the muscles to keep pace with their demands. This leads to the muscles beginning to respire anaerobically leading to the formation of lactic acid. Lactic acid accumulates during the race, however, it is later oxidized through the Krebs cycle or circulated to the liver where it is then converted back to glycogen which obviously requires oxygen which manifests as the so-called Oxygen debt that accounts for the heavy panting that occurs after the race.
- The lactic acid which accumulates during a sprint race has the same effect on the arterioles as carbon(IV) oxide(that is it causes local vasodilatation). Lactic acid also stimulates the aortic and carotid bodies, thereby accentuating the cardiovascular and respiratory responses initiated by carbon(IV) oxide. Carbon(IV) oxide itself will continue to increase because of the oxidation of lactic acid in the Krebs cycle and also because of the way lactic acid is buffered in the bloodstream.
In longer races, however, such as marathon, the oxygen debt may be paid on the run, an equilibrium being reached between oxygen supply and oxygen usage. In short races, the muscles can function perfectly efficiently under anaerobic conditions so long as that oxygen debt is paid immediately afterwards. It therefore means that the performance of vigorous muscular activity at high altitudes imposes some heavy strain on the body, and requires long periods of acclimatization and training before it can be achieved efficiently. This can be observed among athletes living in low altitude countries who usually have difficulties competing favorable with their counterparts from countries situated in high altitudes.