CHAPTER 3 REVISION
Summary
The role of ATP

All energy for muscular contraction and therefore physical activity is produced by the
break down of adenosine triphosphate (ATP).

This energy source is stored in only small amounts within muscles, so the body must
continually resynthesise it for continued muscular effort.

ATP is resynthesised via three energy pathways, anaerobically and aerobically.
The energy systems


Anaerobically, via:
o
the ATP–CP energy system (or phosphate energy system), which uses
phosphocreatine to create new ATP supplies without oxygen. The phosphate
energy system can create ATP very quickly, with a major energy contribution to
powerful exertions of up to around 10 seconds in duration. It depletes quickly,
taking around 3–5 minutes to replenish.
o
the anaerobic glycolysis energy system, which uses glycogen but no oxygen. The
anaerobic glycolysis system takes longer to create ATP. It is the major contributor
to high-level exertions of 10–60 seconds, but creates lactate and hydrogen ions
as by-products.
Aerobically, via:
o

the aerobic energy system, which uses primarily glycogen and fats (and protein
under extreme conditions) and oxygen to create ATP. The aerobic system does
not have any fatiguing by-products and has a high yield but a low rate. Hence it is
the body's preferred system.
All three energy systems are always contributing to ATP resynthesis. This is known as
energy system interplay.
Energy systems and muscle fibres

Fast-twitch muscle fibres are white in colour as they have poor blood supply (do not
require oxygen) and can contract powerfully but fatigue quickly.

As the anaerobic energy systems do not require oxygen and provide energy quickly,
activities that predominantly use the anaerobic energy systems will recruit fast-twitch
muscle fibres.

Slow-twitch muscle fibres are red in colour as they are rich in blood supply (require
oxygen) and contract slowly and repeatedly.

As the aerobic energy system requires oxygen and can provide energy for longer periods
of time, activities that predominantly use the aerobic energy system will recruit slowtwitch muscle fibres.
Strengthen your understanding
1. All energy for muscular contraction comes from which of the following?
1. The foods we eat, in particular carbohydrates, fats and protein
2. The three energy systems working together
3. Energy system interplay
4. The breaking down of ATP
2. Which of the following group of events and sporting examples would predominantly rely
on the ATP–CP system?
1. Shot-put, 200-metre sprint, 400-metre sprint, 50-metre swim
2. Javelin, making a 20-metre lead in AFL, 100-metre sprint, 100-metre swim
3. Long jump, 110-metre hurdles, midfielder in soccer, 100-metre swim
4. Goal keeper in soccer, making a 20-metre lead in AFL, javelin, 100-metre sprint
3. Page 88The anaerobic glycolysis system becomes predominant in activities when
1. CP stores are depleted and there is insufficient oxygen.
2. glycogen stores have depleted.
3. lactic acid stores deplete.
4. there is an increase in intensity.
4. Which of the following is not an advantage of the aerobic energy system?
1. High rate of ATP resynthesis
2. High yield of ATP resynthesis
3. Unlikely to deplete fuels
4. Has the ability to produce energy for a prolonged period of time
5. What heart rate would we associate with a 20-year-old using the anaerobic glycolysis
system?
1. 190–200
2. 170–190
3. 150–170
4. 95–100 per cent of maximum heart rate