Acute exercise and the energy systems

In todays lesson we have discussed the effects of acute exercise on the energy systems. The basis of the responses are formed around a concept called the 'energy continuum'. See below:

The energy continuum is a way of explaining which energy system is predominantly used during different durations and intensities of exercise. We can see that all energy systems are used to regenerate energy all the time, but the predominant one is based on a number of factors.

The ATP-PC system

This system is predominantly used during high intensity short duration activities of up to 10 seconds. The 100m sprint would be a good example. The system produces energy really rapidly, which is a major advantage, but it is limited to 10 seconds as the stores of phosphocreatine deplete rapidly.

The Lactic acid system

This is predominantly used between 10 and 90 seconds, and takes over as the dominant energy provider after out phosphocreatine stores are depleted. This system also creates energy over short duration high intensity exercise, and a good example of a sporting activity would be the 400m sprint. The limiting factor of this system is the build up of lactic acid in the muscles, which stops them from functioning properly. In order to carry on exercising after this time we must drop the intensity, so that our muscles can produce energy through the break down of oxygen and glucose/fat.

The Aerobic system

This system is predominantly used during low/medium intensity exercise, and can last for a long time. The reason why we can provide energy quickly using this system is that it needs to have enough availability of oxygen, and enough time to break it down for energy. A major advantage of this system is that it can provide energy for a really long time (hours, if required). A major limitation to this system is that it cannot produce energy quickly enough for high intensity activity. A marathon would be an example of the body producing most of its energy through the Aerobic energy system.

Using all 3

Our body never really uses just one energy system, and all the time that we are exercising, stores of PC are being regenerated, and lactic acid removal is taking place. This is why an individual playing a team sport such as football or hockey would be able to undertake more than one 10 second sprint in the game - they may have to drop their intensity for a little while, but as soon as their PC stores have regenerated (as little as 30 seconds later) they can then use those stores for another sprint.