Energy Systems

Energy Systems

No matter what sport you play, your body needs energy for top performance. Energy is supplied to your muscles from the food you eat. Your body breaks the food down into usable blocks of energy called Adenosine Triphosphate (ATP). ATP is the immediate source of energy for muscle contraction. Your body makes ATP available for muscle contraction through three main energy systems that are located within the muscle fibers. The energy system used depends on the intensity and duration of the activity.

1. 1. The ATP-PCr, or Creatine Phosphate System, does not require oxygen to produce energy.
   2. Anaerobic Glycolysis uses glycogen stores in the muscle to produce energy without oxygen.
   3. Aerobic Glycolysis uses muscle glycogen to produce energy and occurs in the presence of oxygen.
   4. Oxidative Phosphorylation uses fats stored in the body to produce energy and also requires oxygen.

The ATP-PCr (Adenosine Triphosphate Phospho-Creatine) system is predominant in maximal or super-maximal activities lasting up to 20 seconds.  As the duration of activity increases the ATP-PCr system provides a smaller portion of total energy.  The ATP-PCr system is utilized during the transition from rest to exercise, and also during the transition from one exercise intensity to a higher intensity.  A period of 30 seconds to 3 minutes is needed to replenish the energy in this system, however, during aerobic exercise ATP-PCr reserves can be restored.

As the ATP-PCr system begins to fade after around ten seconds, a process known as Anaerobic Glycolysis begins to occur.  Anaerobic Glycolysis is the primary energy source in activities lasting between 20 seconds and two minutes.  Anaerobic Glycolysis continues to supply energy during exercise lasting up to ten minutes.  This system breaks down muscle and liver glycogen stores without the use of oxygen.  The byproduct of this system is lactic acid.

Aerobic Glycolysis

After about five minutes of exercise, Aerobic Glycolysis is the dominant energy system.  Aerobic Glycolysis produces energy by breaking down muscle and liver glycogen stores with oxygen present.  Because oxygen is present when this system is in use, there is no build up of lactic acid.  This system does not produce energy as fast as the ATP-PCr system or Anaerobic Glycolysis thus the intensity of exercise cannot be as high.  This system has the capacity to produce energy for an hour or more.

Oxidative Phosphorylation

Oxidative Phosphorylation provides the body with energy during exercise of long duration and moderate to low intensity.  This system breaks down the bodies fat stores to supply energy to working muscles.  As the intensity of exercise decreases, the body relies more on this energy system.  This energy system can supply virtually unlimited supplies of energy.  Endurance sports such as cross-country running, swimming, soccer and lacrosse all rely heavily on this system. However, speed and power can often be the determining factor in winning and losing. Therefore careful attention must be paid to developing both energy systems to achieve top performance.

As the graph below shows, all three energy systems are active at any given time, but depending on the intensity and duration of the activity, different systems will be primarily stressed. High intensity, short duration activities stress the ATP-PCr system. As the intensity slightly decreases and the time increases Glycolysis kicks in. Then as the intensity is further reduced and the time increased, the Aerobic System is primarily used.

• • To develop speed and power.
  • To develop your Anaerobic Threshold – The ability to repeatedly perform high intensity work.
  • To decrease recovery time.
  • Quicker removal of lactic acid from muscles.
  • Prolong the onset of fatigue.

• To increase oxygen uptake.
• To increase the muscle’s ability to use oxygen.
• To increase the body’s endurance base.
• To decrease recovery time.