Chapter 4
Now that you have finished ... Answers
1
Explain how ATP provides energy for muscle contractions.
The energy in ATP is stored between the phosphate bonds. When a muscle needs
to contract, a phosphate bond is broken off from the ATP molecule, releasing the
energy it needs to make that contraction.
2
Describe the relationship between the breakdown of each of the nutrients and
the intensity and duration of exercise.
Carbohydrates are broken down easily and can be used to provide energy in high
intensity exercise for moderate durations.
Fats are more difficult to break down but produce more energy. This makes them
suitable for lower intensity exercise that does not require energy to be produce
quickly. Due to the large amount of energy that is produce from each fat molecule,
exercise can be prolonged using this fuel source.
Proteins are only used in times of starvation or after prolonged exercise where fats
and carbohydrate stores are depleted. It is difficult to break down proteins so the
intensity and duration of exercise using this fuel source is minimal.
3
Identify the by-products of energy production for the lactic acid and aerobic
energy systems
The lactic acid energy system produces lactic acid as a fatiguing by-product. The
by-products of the aerobic energy system include heat, carbon dioxide and water
which are easily removed from the body without fatigue.
4
Distinguish the energy system contributions for athletes in the following sports,
events and positions:
a
hockey midfielder
A hockey midfielder would require a combination of all three energy system. The
predominant system used would be the alactacid system. There are many short,
high intensity sprints involved in this position with some time given for recovery of
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the phosphocreatine which would enable this system to be used on and off for the
entire game.
When mid fielder is given inadequate time to replenish pc, the lactic acid system
would provide the energy needed to fuel the athlete. This would occur when high
intensity effort is prolonged or repeated with very short rest breaks.
At times when there are stops in play or when the ball is moved to an area of the
field not controlled by a midfielder, the intensity of effort would be reduced
considerably, enabling the body to access the aerobic system for energy.
b
pole vault
As pole vault is an event requiring high intensity effort lasting less than 8 seconds,
the energy system used by such an athlete would be the alactacid system. The rest
period between attempts would utilise the aerobic system and during this time, the
phospho-creatine stores would be replenished allowing for repeated maximal effort.
c
equestrian
The dominant energy system for equestrian events would be the aerobic system.
The rider needs to stay calm and let the horse do the work. Even though muscular
strength is required, the major energy system is aerobic. Equestrian events can
range from 5 minutes in Dressage and Show jumping, to 24 hours in Enduro
Events. During Enduro events, there is a small contribution of the LA system when
the rider needs to dismount and run up hills to conserve the horse’s energy.
d
200-metre freestyle race.
The lactic acid system would be the predominant system for this event, although all
three systems would contribute. As this event requires a maximal, all out effort, the
alactacid system would be used at the beginning of the race until the phosphocreatine is depleted after about 8 secs. The lactic acid system would supply the
energy where intensity is high but pc is not available. Once lactic acid begins to
accumulate in the muscles (anaerobic threshold) the swimmer would be forced to
slow down and the aerobic system would be able to supply the energy. When each
of these systems is used would vary depending on the race strategy of the
swimmer.
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© Oxford University Press Australia
Outline the factors affecting an individual’s oxygen consumption and delivery.
5
An athlete’s heart and lung function impact upon oxygen consumption and
delivery. Oxygen uptake is dependent upon the stroke volume (how much blood is
pumped from the heart each beat), lung capacity (the amount of oxygen that can
move in and out of the lungs each breath) and the amount of haemoglobin (oxygen
carrying molecules) in the blood.
6
Explain the concept of VO2 max.
VO2 max is the maximum volume of oxygen an individual can consume in any one
minute.
7
a
Outline the adaptations that can occur as a result of aerobic training.
Increased number of breaths per minute, increased size of the lungs, increased
number of capillaries in the lungs, increased size of heart, ventricles and ventricle
walls, increased blood volume, increased haemoglobin, increased muscular size,
increased number of capillaries in muscle fibres.
b
Explain how these adaptations lead to an improvement in performance.
Increasing the number of breaths per minute combined with a larger lung size,
enables more oxygen to be breathed into the lungs and increased capillaries in the
lungs combined with increased haemoglobin for carrying oxygen in the blood
allows more oxygen to be absorbed into the bloodstream. Once in the bloodstream,
the ability of the heart to pump this oxygen quickly to the working muscles can be
improved by the increased size and strength of the heart causing stronger pumps
of the heart. An increased number of capillaries in the muscles allows this oxygen
rich blood to be delivered more quickly and efficiently to the working muscles. By
increasing the size of muscles, the strength of the muscles and their ability to carry
out work will improve.
8
Predict three physiological adaptations that could occur from long-term strength
training.
Muscle hypertrophy (increasing the size of the muscle) is a result of:
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© Oxford University Press Australia
1. An increase in the size of the muscle fibres due to an increase in the number of
muscle fibrils. After strenuous exercise, muscle fibrils will split into two. Each
half of the muscle fibril will grow to the size of the parent fibril, hence, an
increase in size.
2. Muscle fibres will also increase in size due to the increased storage of glycogen,
adensosine triphosphate and phosphor creatine.
3. Muscle fibres (slow twitch and fast twitch) cannot be changed, but each can take
on the characteristics of each other through specific training.
4. Muscle fibres can contract with greater force (an increase in the number of actin
and mysosin filaments which will have an increase in cross bridges required for
contraction)
9
Explain the difference between sub-maximal exercise and maximal exercise.
Sub-maximal exercise is exercise performed at a level that leaves the heart rate in
a plateau (a consistent rate for an extended period of time) below its maximum
number of beats per minute. Generally, this level of exercise can be maintained for
more than 20 minutes at a time. Maximal exercise, however, is activity that leads to
a heart rate that approaches its maximum level and is hard to maintain for a long
period of time.
10
‘Elite athletes are born, not made.’ Using your knowledge of muscle fibres, justify
your opinion about this statement.
There are 3 types of muscle fibres: red slow-twitch fibres, which contain a large
number of capillaries and produce a large amount of ATP slowly; red fast-twitch
fibres, which contain some capillaries and can rapidly produce ATP but fatigue
faster than slow-twitch fibres; and white fast-twitch fibres, which contain few
capillaries and rapidly generate ATP anaerobically. Although an increase in muscle
fibre size and number can be a physiological adaptation to long-term training, an
individual’s genetic make-up determines their proportion of muscle fibre type and
consequently, their suitability to certain sports. An athlete, for instance, born with
large proportions of white fast-twitch fibres will be more suited to sprinting.
Senior Physical Education for Queensland ISBN 978 0 19 557386 2
© Oxford University Press Australia