The Anaerobic Glycolytic System (fast glycolysis)
Glycolysis simply means the breakdown (lysis) of glucose and consists of a series of chemical reactions that are controlled by enzymes. 
Think of the anaerobic glycolytic system as the V6 car engine opposed to the V8 of the ATP-PC system, or the huge diesel engine of the aerobic system.
The anaerobic glycolytic system produces a lot of power, but not quite as much or as quickly as the ATP-PC system. However it has larger fuel supplies (a bigger fuel tank) and doesn’t burn all its fuel as quickly as the ATP-PC system, so it doesn't fatigue as quickly as the ATP-PC system..
The contribution of the fast glycolytic system to energy production increases rapidly after the initial ten seconds of intense exercise. This coincides with a drop in power output as the immediately available phosphagens, ATP and PC begin to run out.
By about 30 seconds of sustained activity the majority of energy comes from the anaerobic glycolytic system. At 45 seconds of sustained intense activity there is a second decline in power output. Exercise beyond this point has a growing reliance on the aerobic energy system, as the anaerobic glycolytic system starts to fatigue.
How does the anaerobic glycolytic system work?
There are four key steps involved in the anaerobic glycolytic system. However they take longer to be carried out compared to the steps in the ATP-PC system. This is why it doesn’t start working as quickly and as these steps are more complex than the ATP-PC system, energy isn't produced as quickly.
Steps of the anaerobic glycolytic system:
- Initially stored glycogen is converted to glucose. Glucose is then broken down by a series of enzymes.
- 2 ATP are used to fuel glycolysis and 4 are created so the body gains 2 ATP to use for muscular contraction.
- The breakdown of glucose to synthesise ATP results in the creation of a substance called 'pyruvate' and hydrogen ions. The muscle becomes increasingly acidic as more hydrogen ions are created.
- Because this system is ‘anaerobic’ there isn’t enough oxygen to break down pyruvate and synthesise anymore ATP.
This results in pyruvate binding with some of the hydrogen ions and converting them into a substance called lactate (completely different to 'lactic acid').
Lactate acts as a temporary buffering system to reduce acidosis (the build up of acid in muscle cell) and no further ATP is synthesised.
What is lactate and what does it do?
For a long time lactate was thought of as the major cause of fatigue and the cause of the ‘burning’ sensation created in muscles during intense exercise. We now know this to be incorrect. Lactate actually helps performance during intense exercise.
During the processes of glycolysis hydrogen ions (H+) are released into the muscle cell. Without oxygen the H+ cannot be removed and as a result the muscle cell becomes increasingly acidic.
It is this acidity that we feel as a burning sensation and it comes about solely as a result of the accumulation of hydrogen ions (H+).
If a muscle cell becomes too acidic the muscle stops functioning as the enzymes that control glycolysis struggle to function in an acidic environment.
During high intensity exercise the products of anaerobic glycolysis namely pyruvate and H+ accumulate rapidly.
Lactate is formed when one molecule of pyruvate attaches to two H+ ions. The lactate is then quickly removed from the muscle cell, protecting the cell from becoming too acidic so exercise can continue for a little longer.
However as intense exercise continues we reach a point where we cannot remove enough lactate from our muscles to control the acidosis caused by the rapid accumulation of H+.
When this happens we are unable to sustain the intensity of exercise and have to either cease exercise or reduce the intensity.
This is why even with the help of lactate we can only work at a high intensity for short periods of time. Bear in mind though that if lactate wasn’t formed we wouldn’t be able to work at high intensity for nearly as long as we can.
The benefits of lactate don’t end there, the lactate that is removed from the muscle is carried to surrounding muscles that have oxygen available and also to the liver where it goes thorough various chemical reactions that ultimately convert it back to pyruvate and or glucose for further glycolysis and energy production via the aerobic energy system.
Training the Anaerobic Glycolytic System
Training this system is aimed at increasing tolerance to lactate, the removal of lactate and improving the rate at which glycolysis produces ATP.
This is the type of high intensity training that ‘burns’ as the active muscles become increasingly acidic.
The work to rest ratios used in this type of training vary depending on the intended outcome.
If you want the system to completely recover and clear the majority of accumulated lactate so you can repeatedly condition it you would use a ratio of 1:6 (6 seconds of rest for every second of work).
A ratio of 1:3 can be used to create a greater lactate response and carry some of the fatigue into the next set of repeats. This helps to condition the body to clear (get rid of) lactate.
With advanced exercisers (you might seriously hurt beginners with this) 2:1 ratios can be used to ‘lactate stack’ an individual.
This ratio causes a progressive accumulation of lactate as the very small rest interval doesn’t allow enough time for much of the lactate to be removed from the muscle. This forces the person to continue to exercise with a lot of lactate present thus dramatically increasing their ability to tolerate the exercise.
So, if I wanted to grow the body’s capacity I’d use a 1:6 ratio repeated often. If I wanted to teach the body to clear lactate I’d use a 1:3 ratio. If I wanted to teach the body to tolerate lactate I’d use either a 1:1 or 2:1 ratio.
Examples of training that focus primarily on the anaerobic glycolytic system are:
- 3 sets of 10 repetitions of any resistance exercise performed relatively slowly (5 seconds per rep) with 2.5 minutes rest between sets. (1:3 ratio)
- Gym circuit class with 45 seconds on each station and 15 seconds rest to move to the next station
- Sprint repeats – 10 repetitions of 30 second sprints as fast as possible with 15 seconds recovery between each sprint (2:1 ratio)
