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6.2.3. Response to exercise. Gap filling.

Read the text and fill the gaps with expressions from the box.

Sources of text:



3-5 minutes


8-10 seconds

anaerobic glycolysis



high energy phosphates

lactate threshold


The body needs energy to exercise; when you start doing exercise (anaerobic or aerobic) the body immediately starts processes to provide energy for the exercise.

This is how the body responds to anaerobic exercise. The first energy source is from , ATP and CP. Energy from this source lasts for about .

 Then, the body gains energy from , also called the lactic acid system.  This can provide energy for about . It uses glucose as a source of energy that is stored in limited quantities in muscle cells. If anaerobic exercise continues longer than that, the production of lactic acid will reach the . This is a point when the production of lactate acid interferes with muscular function.

In the case of aerobic exercise, the body needs oxygen for aerobic metabolism.

Aerobic exercise uses and fat stores. Breaking down is relatively slow and it provides energy for exercise at less than 60% of VO2 max. Carbohydrate metabolism provides energy for exercise up to of VO2 max, because it is a faster process.

During aerobic exercise the body uses carbohydrates from stores in the and the liver. Energy from these stores can last for 80 minutes.  After using up all this energy, the starts using fat stores. 

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