*Note on energy provision
Adenosine triphosphate (ATP) plays the central role in energy provision. From this phosphate we gain the energy that is required by the body for muscle contractions. Only a tiny reserve of ATP is available in the muscle cells themselves, which is used to continually create new energy from available nutrients (carbohydrates, fats and protein).
This occurs in the following ways:
Aerobic (with oxygen) energy supply
Aerobic energy provides energy for longer-term loads, usually for steady-state exercise that lasts longer than two minutes, by “burning” nutrients through oxygen consumption. This aerobic oxidation sequence occurs in 5 enzyme-regulated steps, which in turn are composed of numerous different reactions. The majority of energy required by the body for physical work, especially during longer-term activities, is produced in this manner.
Anaerobic (without oxygen) energy supply
Anaerobic oxidation occurs when a momentary need for energy cannot be met by aerobic oxidation alone. At the outset of a training activity, especially if there has been an insufficient amount of warm-up activity, oxygenation is inhibited by the reduced blood flow to the muscles, which in turn inhibits aerobic oxidation. When the oxygen supply is cut off from the muscle cells in this manner, energy must now be supplied without the help of oxygen, or by anaerobic means. Aerobic oxidation alone is also not sufficient to cover the energy requirements of the most strenuous forms of physical activity. In anaerobic oxidation, the provision of energy stores is created by the breakdown of glucose. There are two different forms of anaerobic oxidation: lactic (can last up to two minutes) and lactic, commonly known as ATP-CP system, which can last up to 15 seconds..
Both forms of energy supply operate concurrently, but with variations in quality and quantity. (cf. De Marees 2003)
An increase in concentrations of lactic acid during periods of physical activity leads to an “overacidification” of the muscle cells, which we perceive as a “burning” sensation in the muscles. This loss of pH then leads to rapid peripheral exhaustion and finally to the abruption of the physical strain. (cf. DeMarees 2003)
The following chart compares characteristics of both forms of energy provision:
|Aerobic Oxidation||Anaerobic Oxidation|
| Energy provision is relatively slow
Released energy quantity per unit of time is relatively small
Total available energy amount is relatively large
i.e. 1000-m run at a relatively slow pace can be maintained for a relatively long period of time
|Energy provision is relatively rapid
Released energy quantity per unit of time is relatively large
Total available energy amount is relatively small
i.e. 400-m-run at relatively fast pace can be maintained for only a short period of time
(Ill.: Characteristics of aerobic and anaerobic oxidation (as per DeMarees, 2003)
The maximal oxygen uptake (how many milliliters of oxygen can be consumed by the body per minute) is the central criterion for endurance capacity and plays an important role in aerobic forms of endurance activities. Maximal oxygen uptake can be improved with endurance training activities, making endurance training an extremely important and highly recommended form of physical training for the maintenance and regeneration of overall physical health. (cf. De Marees 2003).