IAAF "Introduction to Coaching Theory"

The Energy Systems

    In order to determine how energy is produced in our muscles we have to consider some important factors:

"Is air, in the form of oxygen, required?"
If it is, we say the energy system is aerobic.

If not, it is anaerobic.
"Is lactic acid produced?"
If it is, we say the system is lactic.
If not, and no air is required, it is alactic.

    So, there are three energy systems operating in the bodies of our athletes. One of these is aerobic, with oxygen and two are anaerobic, without oxygen:

● Aerobic System
    The muscle energy system which requires oxygen.

● Anaerobic Alactic System
    The stored, start up system which does not require oxygen and does not produce lactic acid.

● Anaerobic Lactic System
    The system which does not require oxygen but produces lactic acid.

    The athlete's body is capable of using one or any combination of the three energy systems. Different events demand different types and amounts of muscle activity. Consequently, different energy systems predominate in the various events. Improving performance is often the result of carefully designed training programmes that aim to increase the capability of specific energy systems and muscles.

The Aerobic-Anaerobic Split
    The aerobic-anaerobic split refers to how much the aerobic and anaerobic energy systems are involved in a particular activity. Marathon runners, for example, produce most of their energy aerobically, while sprinters, jumpers and throwers depend more on anaerobic sources. The aerobic- anaerobic split is determied by identifying how long and how hard our athletes work without rest.

    There are two important work times that mark a shift in emphasis from one of the three energy systems to another:

10 seconds--After 10 seconds of intense muscular activity the energy system providing the majority of the energy shifts from the anaerobic alactic to the anaerobic lactic system.

1 minute---After about 1 minute of intense activity the shift is away from the anaerobic lactic system to the aerobic system.

The Endurance Energy System
    The aerobic system requires oxygen. This system is used in lower intensity exercise and is the basic system which provides the energy for most human activity from birth to death. As such it is also important in recovery from exercise of all intensities. It is very efficient and does not produce fatigue producing waste products. The heart and lungs are important in aerobic activity as oxygen and fuel are carried to the muscles in the blood.
    The aerobic system resists fatigue. It takes longer to overload than either of the anaerobic systems. Training the aerobic energy system must be a minimum of 20 minutes duration. The work load for aerobic training can be either continuous or broken up into intervals of harder and easier running. Correct aerobic training will improve aerobic energy production in the muscle and also improve the support of the heart and lungs, the oxygen transport system.

Anaerobic Alactic Energy
The 'First 10 Seconds' Energy
    The anaerobic alactic system is the one referred to as the stored or start up energy system. This system provides the majority of energy when our athletes do bursts of high speed or high resistance movements lasting up to 10 seconds. The stores of energy in the muscle which are used up in the intense burst of activity return to normal levels within 2 - 3 minutes of rest.
    The anaerobic alactic energy system is developed by alternating periods of work and rest. The work time should be very intense, but not exceed 10 seconds, as this is the limit of the energy system. The rest periods should be 1½ to 3 minutes, depending on the duration of intense activity, to allow the muscle energy stores to build up again. If an athlete shows the effects of fatigue, allow more rest time or decrease the work time.

Anaerobic Lactic Energy
The '10 Seconds to One Minute' Energy System
    This energy system is capable of high levels of intensity, but this intensity prevents the removal of waste products because not enough oxygen is available. The system operates without oxygen. As a result lactic acid accumulates within muscle cells and blood. This is a major cause of fatigue, which eventually slows the athlete. The more intense the exercise rate, the faster the rate of lactic acid accumulation to high fatigue causing levels. For example, the 400 metre sprinter will accumulate high levels of lactic acid after 35-40 seconds. The 800 metre runner runs more slowly and accumulates lactic acid at a slower rate, reaching high levels after about 70-85 seconds.
    Getting rid of lactic acid after activity is a much slower process than the replacement of energy stores in the anaerobic alactic system. It may take more than one hour for lactic acid levels to return to their pre-exercise level. Light activity such as walking or jogging following intense efforts speeds up the removal of lactic acid. The first ten minutes of active recovery produces the greatest reduction in lactic acid levels.
    The anaerobic lactic energy system is developed by intense work loads of 10 seconds to two minutes duration. Rest periods will depend on the duration of the work and should be three to ten minutes to allow removal of most of the lactic acid produced.