After about three minutes of low intensity exercise, ATP is almost completely supplied from the third system As you can see, which system the ATP comes from depends upon the intensity and duration of the exercise. The first step in setting up a conditioning program is to determine the energy system used by the activity according to the intensity and duration of it. Then a similar type of activity is used for conditioning. That way the proper energy system will be trained. Your conditioning program should be based on interval training principles.
Interval training is work or exercise followed by a prescribed rest interval.
The program must meet the specific conditions for each sport. A common training error that coaches make in their conditioning programs is making the rest intervals too short. If the rest period is too short, the amount of energy is not sufficient to meet the demands of the next maximum intensity effort, and force output will be reduced. This problem is very common. Coaches who make the rest interval too short, cause the force to be reduced, and in this case slow twitch muscle fibers are trained rather than fast twitch fibers.