Energy Systems – Police Fitness

Three Energy Systems

The are three energy systems that our body uses. The food we eat provides the fuel but the body has to break down that fuel from a biological state to an chemical state.

MACRONUTRIENTS

The three macro nutrients are carbohydrates, fat and protein. The body can utilize each of these as energy but, unless absolutely necessary, it will spare protein

Protein, in the form of amino acids, is needed to repair the body and is used in many of the processes in the body.

Carbohydrates, plant based food, and the different fats are the main choices for our energy systems. Carbs are broken down into glucose and starches. Glucose is stored in the liver and muscles as glycogen. When needed the body will change the glycogen back into glucose and then into energy.

Fats are stored as triglycerides and, when needed, will become free fatty acids. In the triglyceride molecule are three fatty acids attached to a glycerol spine. These break down and rebuild constantly. The free fatty acids enter and exit the bloodstream as a result.

Therefore, both glucose and fatty acids are in our blood , to be transferred into energy.

Adenosine Triphosphate (ATP)

Through a chemical process, the macronutrients are broken down to form ATP. This molecule is the main source of energy used by the body. Although the way it is used by the body is the same each of the three energy systems uses it differently.

The systems

The three energy systems are the ATP-CP system, the glycolytic system, and the oxidative system.

ATP-CP (Phosphagen)

The body stores a limited amount of ATP in its muscle. This energy is very limited and is useful for short, intense power outputs for up to 15 seconds. The fifteen seconds is for highly conditioned people. Most of us would only have between eight and ten seconds of this energy source available to us.

When expended, the body uses phosphocreatine to resupply the ATP. One reason creatine monophosphate is used as a supplement is to supply the body with creatine phosphate. The body is more than capable of producing creatine phosphate on its own.

The ATP-CP system does not use oxygen. It is an anaerobic system and is formed outside of the mitochondria. Anaerobic means without oxygen.

The ATP-CP system is also called alactic as it doesn’t produce lactic acid.

This energy system is used for explosive events such as jumping over an obstacle or the initial 50 – 75 sprint when chasing a suspect. Since this fuel system is only viable for a short period of time, the next system needs to kick in. If it doesn’t, we would drop to the ground, unable to move – exhausted!

Glycolytic System

The glycolytic system is also anaerobic. Just as the body stores ATP in small amounts in the muscles, it also stores glycogen in the liver and muscles. As well, there is glucose circulating in the blood. This glycogen mainly comes from the consumption of carbohydrates. If a person is on a low carbohydrate or a non-carbohydrate diet, the body is able to produce glycogen from either fat or the muscles.

The fuel available in the glycolytic system is also limited. The glycolytic system’s power output is less than that of the phosphagen system. It will sustain a good power output for up to three minutes. Again, the more trained a person is, the longer this energy system will sustain the power output.

One of the chemicals produced with this system is lactic acid.

Struggling with someone resisting arrest evokes this system. The better you have trained this system, the longer you can endure the struggle before exhaustion. Because this energy system is anaerobic or without oxygen, when you are finished with the arrest you are panting like a dog. Your glycolytic system is nearing depletion, and your body is trying to switch to the third system so you can still work.

In track and field events the 100 and 200 meter races are known as sprints as they will use these first two systems.

Boxers or MMA participants will crash and slow down because they have not trained the glycolytic system properly. Police officers will also crash if they neglect training the glycolytic system!

aerobic system (Oxidative)

The aerobic energy system, as the name implies, uses oxygen to supply energy. The main processing plant is the mitochondria. Both glucose and fat are burned for fuel. This is represented in the long, slow run or bike ride. The main energy source is fat, although as intensity increases, glucose is used more.

This system can take longer to become fully functional. When we go on a run and say, “I just caught my breath,” it indicates that we have switched to this system.

One of the limiting factors for this energy system is how strong our lungs are. This is represented by the maximum volume of air we can get into and utilize. It is called VO2 Max. Another limiting factor is the ability of the body to burn fat as fuel efficiently. In a long run, as the muscles get fatigued. Maintaining the same pace requires more energy. The body, because of the increase in energy needs, will start to burn through the glycogen stores and may deplete them. This is called “hitting the wall” or “bonking”

The body usually has enough stored glycogen to keep us going for about 90 minutes.

The intensity of an activity can cause the body to go to one of the other systems. Remember that the glycolytic energy system has a byproduct called lactic acid. When completing an aerobic activity if the intensity gets too great you will cross the lactic threshold (LT) and will start to produce lactic acid. This will reduce the energy output your muscle can produce and sustain.

energy systems work together

Although it seems like there are three independent systems with a progression from one to the other, in actual fact, all three systems are at work together. The intensity and duration decides which is the primary energy system.

Human Kinetics estimates the following energy systems percentages in the 100m, 1500m, and marathon.

Distance	ATP -CP	Glycolytic	Aerobic
100 meters	95%	3%	5%
1500 meters	20%	55%	25%
Marathon	5%	5%	90%

Energy system Distance. 100m. 1500 m. Marathon

Determining the best energy system for police work

All three energy systems need to be trained for police work. So often the aerobic system is trained exclusively. Yet, it is the ATP-CP and the Glycolytic systems that the police are usually taxing.

The next Police Fitness blog will be about exercise choices and program design