October 5, 2009 in Energy Systems by James Dawson Martin

The Human Energy Systems

Energy Systems – By James Dawson Martin.

The energy our body requires to produce movement, force against objects, grow or generate heat comes from one place – a substance in the body known as adenosine triphosphate, ATP for short. This is a form of energy provided by the macronutrients (protein, fat, carbohydrates) in the food that we eat, with fat and carbohydrate stores being the perferred energy sources. ATP = ENERGY.

ATP is what provides the energy to allow for muscular contractions – working out. Therefore, as long as ATP Supplies are sufficient to meet our exercise demands, muscular activity of any kind can occur and continue.

The body has three distinct energy systems to meet the ATP demands;

• The Creatine Phosphate System – 0-10 seconds high intensity, short burst activities – uses purely chemical energy as fuel
• Lactate System – 1-3 minutes high intensity activity – uses carbohydrates as fuel
• Aerobic System – long duration, low intensity activity – uses carbohydrates and fat as fuel

The creatine phosphate system:

For high intensity, low duration physical activities (heavy weight training, sprinting, etc) energy for muscular contraction is required quickly and in short bursts – this is supplied within the muscle stores of ATP and creatine phosphate.
These ATP stores are extremely limited and may only last for the first few seconds of exercise – 5 to 8 seconds.

This system, the creatine phosphate system, comes exclusively from chemical energy stored within the muscles, and the process requires no oxygen (anaerobic) and places no immediate demands on fat or carbohydrate stores like lactate and aerobic energy stems.

Recovery rates usually range from 30 seconds to 4 minutes.

This system is utilized for when we do heavy, high intensity and low duration exercise and sports. For example, a one rep max on your bench.

Lactate System

The lactate system is associated with the burning sensations felt during high intensity activities. The lactate system bridges the gap between aerobic and creatine phosphate systems. It allows for energy to continue beyond the few seconds of the creatine phosphate energy system, and at a rate greater than the aerobic system can achieve. Exercise can be sustained for between 60-180 seconds.

Even when we rest, small amounts of ATP energy are produced using the lactate system – there is always a small amount of lactate present in the blood. During low intensity activity, our energy requirements are easily met using the aerobic system. However, when the energy demands of an activity become too great for the aerobic system to manage, the lactate system starts to be utilized and blooc lactate levels will start to rise.

The rate of energy production from the lactate system is rapid and the fuel is glycogen/carbohydrates.

The duration of activity would be 1-3 minutes of intense activity.

Recovery rates vary from 20 minutes to two hours, which is dependent on the intensity and duration of exercise.

Think of an example lactate activity as being a 400m sprint or a high rep set of weights.

Aerobic (oxygen) system:

Aerobic means ‘with oxygen’, and refers to the energy system that produces ATP (energy) from the complete breakdown of carbohydrates and fat, with oxygen being present.

The aerobic system is dominant during lower intensity activities when ATP energy demands are low and oxygen is relatively plentiful.
At rest or during low intensity activity, most aerobic energy is supplied by fat. As exercise demands increase and ATP is required more quickly, carbohydrates will begin to contribute more to the process. Protein contains as many calories of energy as glucose/carbs, but it will contribute little to energy production so long as sufficient carbohydrate levels are available. If not, protein is utilized and muscle breakdown can occur.

The rate of energy production from the aerobic energy stem is s low and uses glycogen/carbohydrates and fat as fuel.

The activity used for this kind of energy system is a low intensity, long duration time of activity.

Recover is usually fast – just replenish the stores by eating or drinking a mixture of carbohydrates and protein.

Think of aerboic activity as being a long distance walk – something that does not require much energy.

I hope this gives you a basic idea of the three energy systems our body utilizes for different forms and different intensities of activity.

Best to you all,

James