The body has three different energy systems. One of them is aerobic, that is it uses oxygen, the other two are anaerobic and do not use oxygen. The body has three different energy systems. One of them is aerobic, that is it uses oxygen, the other two are anaerobic and do not use oxygen.
Aerobic system - the energy provided by this system has no detrimental by-products and provided there is an adequate supply of oxygen will last indefinitely.
Alactic system - is the start-up system known as phosphocreatine system that combine with a substance called ADP within the muscle cell to produce energy. This stored energy has no by-product and lasts for anything between 10 and 20 seconds depending upon the intensity of the work. With appropriate training, the phosphocreatine level in the body can be raised up to 300 per cent.
Lactic system - is the main anaerobic system, energy is produced and a by-product, lactic acid results. The energy produced by this system can last up to 2 minutes but then the lactic acid build-up produces fatigue in the muscles.
The relationship between these systems is very important because it will dictate how we adapt our endurance training to suit our needs. All three systems work alongside each other and are inextricably linked together, but it is often useful to examine them separately for the purposes of designing training programs. It is important to realize that the muscle will normally bring in the anaerobic cycles only to supplement the aerobic mechanisms when they are fully stretched.
Imagine you are about to start a steep climb that will be demanding straight away:
The muscle cells hold very little in the way of stored oxygen, therefore, as you start the pitch, the energy will have to come from the anaerobic system since at this moment the aerobic system cannot cope.
The lactic system takes a short while to get into gear (as the chemical chain starts to operate) so it is the alactic system that provides the initial source of energy (it is the start-up system).
By the time the supply of phosphocreatine runs out, the lactic system should have reached full flow and it will take over. During this period an oxygen debt will have built up and until it is cleared (usually within a few minutes) the exercise will fell harder.
Once a steady state is reached and you get second wind the aerobic system will have take over.
For example, if the climb suddenly steepens, putting more demand on the muscles, the aerobic system may not be able to supply enough energy, and the anaerobic system is then employed.
If the steep section is long and sustained, the muscles will continue to work anaerobically, the elactic cycle rapidly running out of supplies thus causing the lactic system to take on the workload. It is this system that produces lactic acid and a build-up of this causes the all too familiar "pumped" sensation. If we cannot relieve this fatigue then eventually we will run out of strength and fall off.
It follows from the scenario above that the more efficient our aerobic system is the better since this will put off the employment of the anaerobic cycle with its penalties. Having done that you can then work upon your anaerobic endurance, improving your reserves of phosphocreatine and improving the mechanisms of producing and clearing lactic acid.
The rest intervals (3-5 minutes) in anaerobic training are vital. They allow time for the clearance of lactic acid, which takes place in two stages, firstly into the blood and secondly out of the blood.
