Anaerobic vs. Aerobic Energy
How Anaerobic and Aerobic Energy Powers
Muscles?
In simple terms, how muscles are powered
varies according to the time spent exercising. To begin with, (about the
first two minutes of exercise), the body cannot get enough oxygen to supply
the heart and muscles which need to work faster than normal. So the muscles
are forced to rely upon non-oxygen sources of energy (anaerobic). Then,
as the supply of oxygen rises, muscles move into aerobic metabolism. As
follows:
Stage 1. Anaerobic ATP-PC Energy System
This occurs during roughly the first 15 seconds
of continuous exercise. The muscle is powered by energy-rich ATP (adenosine
triphosphate) molecules (located in the muscle itself). If muscular contractions
continue for longer than this, the energy must be sourced from glycogen,
which is also stored in the muscles.
Stage 2. Anaerobic Glycolysis
This occurs during roughly the first two
minutes of continuous exercise. During this time, once ATP-PC is exhausted,
the muscles are supplied with energy from their own glycogen sources.
[Glycogen is blood-glucose, specially stored in the muscles.] If you exercise
continuously for longer than about 2 minutes, you eventually burn up all
of the glycogen stored within the individual muscle.
Stage 3. Energy from Glycogen During Aerobic
Activity
This stage lasts for about 20 minutes. During
this period of continuous exercise, if you breathe correctly, the muscles
are powered by more glycogen (stored blood-glucose) which comes via the
bloodstream from the liver (and other muscles) to help you continue exercising.
Stage 4. Aerobic Fat-Burning
This is the final stage. After about 20 minutes
of continuous exercise, the body's stores of glycogen become exhausted,
and the body starts using stored body fat for fuel to power the muscles.
This process of fat metabolism occurs in the presence of oxygen. This
is how sustained aerobic exercise helps to burn fat and thus causes weight
loss. In fact, the body continues to burn body fat - even after your exercise
has ceased - which it converts to blood glucose and uses to replenish
its stores of glycogen in the liver and muscles. Thus fat-burning continues
for several hours.
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