What Is The Alactacid System (ATP-PC)?

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The alactacid system is utilised by the body in order to produce ATP when there is not sufficient time to break down glycogen in the presence of oxygen in order to replenish ATP. While ATP is being broken down in the muscle, another high-energy substance—which is called phosphocreatine (PC)—is also being broken down.

The cells contain more PC as opposed to ATP so PC can be considered as  phosphate reservoir. The breakdown of PC creates energy, which is used to join ADP and P back together in order to produce ATP.  The amount of PC in a person’s muscles is limited.  After about five to 10 seconds of maximal exercise the supply is depleted. This reduces its capability of contributing to movement. As a result another energy system is activated.

What Type Of Exercise Uses The Alactacid System?

High-intensity exercise that lasts for 10 seconds or less utilises the alactacid system as the primary source of energy. Such activities include the following:

  • Shot put,
  • 100-metre sprint,
  • Jump shot, as well as
  • Kicking a football.

As the supplies of PC are broken down, they are quickly restored – within two minutes if resting. This allows for the exercise to be repeated in intense, short bouts, without instant exhaustion.

The only way that PC may be restored is to re-combine the P and C – which has been released – in order to resynthesise ATP. This is done in the process of recovery. This system represents the most easily available source of ATP for use by the muscles. There are a number of reasons for this, including the following:

  • It is not dependent on a long series of chemical reactions.
  • It is not dependent on transportation of oxygen to muscles.
  • Both ATP as well as PC are stored in the contractile tissue of muscles.

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What is The Performance-Decrement Test?

The objective of the performance decrement test is to measure the degree to which performance will be affected by participating in various intensities of exercise

Here’s the equipment that you’ll need:

  • Measured distances of 35 and 70 metres
  • Whistle, pens, recording sheet as well as witches’ hats
  • Stopwatches (one for each person taking part)


  1. Subjects should warm up.
  2. Timers need to stand at the timing line, in other words, the 35-metre mark along the 70-metre track. Timers will record each sprint time as subjects cross the line.
  3. Subjects begin at one end of the line and prepare to run towards the other end of the line.
  4. When the whistle is blown, the subjects sprint 35 metres in order to cross the timing line. They then slow down and jog or walk to the other end of the line.
  5. The subjects turn, rest and then prepare to sprint in the opposite direction. Six 35-m sprints are done: three in each direction. The time between whistle blows (that is, between sprints) is 30 seconds. A five-second warning signal is given before each of the whistle blows.
  6. Each 35-metre sprint is timed to the nearest 0.01seconds. Then the time recorded.
  7. If a subject begins a sprint before the whistle, the run will not count. That individual will have to run an extra sprint.
  8. At the end of the sprint, partners have to record (on the recording sheet) the feelings of the subject by asking questions about breathing, feeling in the legs and overall body feelings. The subject’s heart rate is also recorded.
  9. Once the sprint distance has been covered, the subjects must continue to jog or walk until their heart rates returns to resting levels. Record the time that this takes.
  10. The subjects then change roles with their partners.

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Having a good understanding about what happens to the body’s systems during exercise is crucial information that the personal trainer needs. If you are interested in learning more – and becoming a personal trainer – then you should check out our Personal Training Diploma. Follow this link for more information.

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