During exercise,
 your body relies on three basic energy systems: the anaerobic a-lactic 
system, the anaerobic lactic system, and the aerobic system. Depending 
on the sports played, athletes rely on one system more than the others. 
An understanding of the involved energy systems in a particular 
sport gives valuable information about the strength qualities necessary 
in that sport. This information gives the personal trainer or strength 
coach clues on how to conduct the strength training. 

The Three Basic Systems
 
 
1. Anaerobic A-Lactic (ATP-CP) Energy System
 
 - 
  The anaerobic a-lactic (ALA) system, also known as the ATP-CP, or 
adenosine triphosphate - creatine phosphate system, provides high bursts
 of start-up energy for activities that last less than ten seconds in 
duration. 
  Athletes who compete in sports that require high amounts of short duration acceleration - shot-putters, weight lifters, gymnasts,
 or sprint-distance speed skaters use the anaerobic a-lactic system. The
 ALA system does not create energy for sufficient duration to create a 
great deal of waste products.
2. Anaerobic Lactic (Glycolytic) Energy System
 
  
- 
  The anaerobic lactic (AL) system (also known as fast glycolysis) 
provides energy for medium to high intensity bursts of activity that 
lasts from ten seconds to two minutes. Some 
 American football skill positions, 
 baseball players, 
 soccer players, 
 judokas, 
 middle distance runners (400m-800m) and 
 sprinters
 rely on this system. The anaerobic lactic system, as well as the ATP-CP
 system, are capable of high intensity levels, and do not rely on oxygen
 for fuel. 
  The primary difference between the two systems is in the capacity 
of the system. You can think of capacity as the amount of time that the 
system can work at peak output before dropping off. 
Whereas the ATP-CP system will only produce energy for 10 seconds, fast glycolysis works at capacity for as long as two minutes. As a result, waste products such as lactic acid accumulate in the blood and in muscle cells. A burning sensation in the muscle, shortness of breath and fatigue are all symptoms of lactic acid build up.

3. Aerobic Energy System
 
  
The aerobic system is the most utilized of the three. It provides 
energy for low intensity activities that last anywhere from two minutes 
to a few hours. Unlike the other two systems, the aerobic system 
requires oxygen and takes much longer to overload. Sports and activities
 that use continuous sustained efforts such as 
 long distance swimming, crew (rowing) and sea kayaking rely on the aerobic system. 
 
In reality, most sports use a variety of energy systems, or at 
least the power (time to reach peak output) and the capacity (duration 
that peak output can be sustained) of the system. The only real 
exceptions are Olympic weight lifting and certain field events, such as 
hammer or shot put. Which is energy system is most prevalent in a given 
sport dictates the training intent. 
Reference: Bindu Nambiar (bodybuilding.com)
