Here I will discuss the three main systems of energy release which are used by the body. In order to do this I will use a graph which I will then explain for their use in each sport.
three main energy systems used by the body are-
1. ATP-PCr system (phosphagen system) – This system is non oxidative in nature and only lasts for around 7-14 seconds depending on how trained the individual is. As you can see on the graph, the light blue curve peaks at just before 10seconds. This is where it is at its maximum capacity and performance of this system will be best. After the peak % of energy production, the system begins to drop off and performance quickly decreases! 1 mole of ATP is produced per 1 mole of phosphocreatine (PCr). ATP (adenosine tri-phosphate) is the main source of energy to the body, in this system, there is a small amount stored next to fibrils, this is stored as CP (creatine phosphate).
To develop this energy system, sessions involving repeats of up to 10-15 seconds of maximum intensity activity/work are required, with approximately two minutes rest between repeats to allow the system to replenish.
The athletes which use this system are short distance sprinters (-100m), heavy weight lifters (using max power to lift 1-3 reps), shot putter, goalkeepers in soccer and any athletes which use a short burst of energy which needs quick 7-14seconds of sharp energy.
2. Glycolytic system – Anaerobic Glycolysis: breakdown glucose with limited O2-rapid formation but limited to approx 50 seconds. This system is seen by the red curve on the graph! Through this process glucose is used and broken down from its 6carbon compound to 2X pyruvic acid, this process releases energy (ATP). Energy release is used to form ATP (4x) (net gain 2x). The rest of the energy is lost through the body by heat! However this ATP is then used to service this glycolytic system. Glucose can continue to be broken down to provide energy for up to around 50 seconds. This system is inefficient but fast. It builds up an O2 debt- which is the amount of oxygen needed to clear the lactic acid. Prolonged use will lead to cramping and muscle pain due to this build up of lactic acid.
Training of this system is aimed at increasing the bodies tolerance to lactic acid, removing the lactate and improving the rate at which glycolysis produces ATP. This requires changing the ratio of work to rest and pushing the system, we will get to this later in my blog!
The athletes which would use this system are short distance runners or swimmers who travel around 200-400 meters, crossfit trainers, gym classes where participants move from machine to machine in sections of 30-45 seconds, soccer players and circuit trainers. This system can be dangerous for marathon and long distance runners as if they put in a stronger burst than their set pace, it could lead to the build up of lactate and a more difficult run!
3. Oxidative system – This system is seen on the graph as the green line! Using O2 creates large amounts of energy ‘unlimited’. This system can provide unlimited supplies of energy though the use of oxygen. This system uses about 30% of glucose to produce the ATP needed, and 70% use of fatty acids, this is the main method for weight loss as these fatty acids are being burned to create energy! This system can utilize fats, carbs and proteins to produce the needed energy however! This system can produce large quantities of energy, however it does so quite slowly so cannot service intense exercise! It uses three advanced systems to produce this energy, however for now we will stick to the basic physiology side of the energy systems and their uses!
Training this system can be done through interval training with a very low ratio of rest to exercise 1:1 or 1:2, continual training can be done which involved constant movement at a set pace for over 15 minutes (long distance running!). Fartlek training is another way of training this system which is a type of interval training whereby the exerciser varies the speed and effort throughout the training session according to how they feel ensuring that they can continue to exercise at all times (i.e. no rest intervals).
Athletes who use this system are long distance runners requiring a slow but constant supply of energy! Cyclists, swimmers and joggers also use this system!
As an added point, I would like to add that Carbohydrates and Proteins contain 4 calories per 1g and Fat contains 9 calories per 1g. These calories add to energy supplies however it is something to take into mind for someone trying to lose weight! I feel people would benefit from looking at fat contents more so than calories, saturated fats are the main issue and in my opinion calories are not a good way of measuring intake. Some foods provide valuable calories while others have empty calories, this is something food guidelines wont highlight!
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