The energy systems

The Energy Systems: An Overview

  • Energy systems refer to the ways in which the body generates and uses energy to sustain physical activity.
  • The body has three distinct yet interconnected energy systems: the ATP-PC system, the glycolytic system (or lactic acid system), and the oxidative system.
  • These systems are fuelled by the body’s stores of adenosine triphosphate (ATP).

ATP-PC System

  • The ATP-PC system (A for Adenosine triphosphate, P for Phosphocreatine) is an anaerobic energy system, meaning it doesn’t rely on oxygen.
  • This system provides immediate energy for sudden bursts of intense activity lasting 0-10 seconds, such as sprinting or jumping.
  • When the ATP stores are used up within a few seconds, PC breaks down to release energy that resynthesizes more ATP. When the PC stores deplete, the body has to move to other energy systems.

The Glycolytic System

  • The glycolytic system (also known as the lactic acid system) is also anaerobic, and it uses the breakdown of glucose to produce ATP.
  • This system provides energy for moderate-to-highly intense activity lasting between 10 seconds to 2 minutes.
  • During this process, glucose is broken down into pyruvate which produces ATP. If there’s insufficient oxygen, the pyruvate turns into lactic acid leading to fatigue.

The Oxidative System

  • The oxidative system, also known as the aerobic system, uses oxygen to produce ATP. It relies on the circulatory system to deliver the oxygen to the muscles.
  • This system generates energy for longer, less intense activity lasting from 2 minutes to several hours.
  • The oxidative system breaks down carbohydrates (glucose), fats (fatty acids) and sometimes proteins (amino acids), in the presence of oxygen, to produce ATP, carbon dioxide and water.

Importance of Energy Systems in Physical Activity

  • Understanding the three energy systems can help to improve performance in sports and physical activities.
  • Athletes often train to maximize the efficiency of these energy systems by appropriate energy system targeted training.
  • Knowing when each energy system is most active helps shape training protocols and diet plans to meet energy demands.
  • Replenishing ATP stores is crucial for recovery after physical activity.