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Factors Affecting Performance
HSC Core 2
How does training affect
performance?
• Energy systems
– Energy is produced by the breakdown of adenosine
triphosphate (ATP) to adenosine diphosphate (ADP) and
inorganic phosphate (Pi). Muscle cells can only store limited
amounts of ATP, so must also be able to replenish it.
– When ADP combines with creatine phosphate (PC), more ATP is
produced. If this occurs in the absence of oxygen it is referred to
as anaerobic metabolism.
– If it occurs in the presence of oxygen it is referred to as aerobic
metabolism.
– This cycle of energy breakdown and production continues,
providing the amount of energy required at any given time. The
energy needed depends on the intensity and duration of the
activity.
• The body has three energy systems that
rebuild ATP:
1. the alactacid or ATP/PC system
2. the lactic acid or glycolytic system
3. the aerobic or oxidative system.
The three energy systems
Alactacid system (ATP/PC)
• The alactacid system is the quickest way to
produce ATP, and is predominantly used for
short-duration, high-intensity activities such
as diving, long jump and sprints.
• This system also supplies ATP at the beginning
of any form of exercise, regardless of intensity,
as it can perform without oxygen.
• There are only limited stores of ATP
(approximately 80 grams) and PC (approximately
120 grams) within muscle cells, these are
depleted within 6–8 seconds of maximal work.
• If maximal exercise lasts longer than this,
assistance from other energy systems is required.
• Therefore a 100-metre sprint is fuelled by both
the alactacid and lactic acid energy systems. ATP
and PC levels reach approximately 50 per cent
after 30 seconds of rest, and are fully restored
within 2–5 minutes.
The alactacid energy system
Lactic acid system
• When PC stores have been depleted (after
approximately 8 seconds of maximal effort),
the lactic acid energy system becomes the
dominant supplier of ATP.
• This coincides with a decrease in maximal
power output or running speed.
• At about 45 seconds there will be another
decline in power output as the body becomes
more reliant on the aerobic system for energy
The conversion
of lactate
to glucose
An athlete predominantly uses the lactic acid energy system when competing in the 400
metres
• The lactic acid energy system relies on a type
of glycolysis called anaerobic glycolysis (often
referred to as fast glycolysis) to produce ATP.
• The increased concentration of lactate during
moderate exercise can be converted to
pyruvate and used to synthesise glucose in the
liver.
• This new glucose can then be used as an
energy source during exercise.
• Therefore lactate is a potential source of
energy, and can delay the decrease in blood
glucose levels.
Aerobic system
• The aerobic energy system is the most
complex of the three energy systems.
• It is the primary source of ATP at rest and
during low-intensity exercise.
• Carbohydrates, fats and proteins are used as
fuel sources.
• Energy release from fats is very slow, it must
be converted from triglycerides into glycerol
and free fatty acids.
• Although 1 gram of fat produces more energy
than carbohydrates (9 kilocalories from fat,
versus 4 kilocalories from carbohydrates), it
requires more oxygen.
• As exercise intensity increases there is a greater reliance on
ATP production from glucose (energy is released much
quicker) and less on fats.
• Aerobic glycolysis (or slow glycolysis) is used to produce this
ATP.
• This process involves the partial breakdown of glycogen or
glucose in the presence of oxygen to produce ATP, with
pyruvate as the end product.
• The longer the duration of continuous exercise—more than 1
hour of continuous exercise, or more than 3 hours of
intermittent exercise—the more important fat will be as a fuel
source, as glycogen stores become depleted.
With training, the body learns to use a combination of
glycogen and fats as fuel during competition (such as a
marathon) so there is glycogen available at the end of the
race to ‘sprint’ home.
The amount of energy stored in the human body
After 1 hour of submaximal exercise approximately 50 per cent of energy is derived
from carbohydrates (muscle glycogen and blood glucose) and the other 50
per cent from fats and muscle triglycerides.
Protein contributes little to ATP production, except in prolonged exercise
where it can be broken down into amino acids and used for energy when
glycogen is low.
Percentage of
energy
derived
from
carbohydrates
and fats
during
submaximal
exercise
The aerobic system can supply energy for low-intensity exercise lasting several hours.
Relative
contribution
of energy
systems to
ATP
production
during
maximal
efforts of
6–25 seconds
Relative
contribution
of energy
systems to
ATP production
during
maximal efforts
of
2–3 minutes
Energy contribution (percent)
The Energy Systems Working Together
100
Oxygen (aerobic) energy
50
Anaerobic
{ Lactic acid energy
{
{ Alactacid energy
0
0 10 20 30 40 50 60
120
180
240
300
360
Running time (seconds)
The chart shows although one system may be dominant at one time, all systems work together to supply energy.
Their role and contribution depends on :
•
type of activity
* duration of effort
* intensity of work
•
http://www.authorstream.com/Presentation/mphillips-83412-energy-systems-systems1-education-pptpowerpoint/
The Alactacid System
system)
(ATP/PC
The alactacid system (ATP/PC) System :
 Provides energy for explosive work
 Is exhausted within 10-12 seconds of maximal work
 Is fuelled by creatine phosphate
 Makes ATP rapidly available
 Fatigues rapidly when creatine phosphate supplies are exhausted
 Has no fatiguing by-products
 Recovers in about 2 minutes
Creatine phosphate is an energy-rich compound that serves as an alternative energy source for
muscular contraction
The Lactic Acid System
The lactic acid system :







Provides energy for activity once CP supplies are exhausted
Functions for about 2-3 minutes and fills the energy gap before oxygen reaches cells
Is anaerobic; that is, does not require oxygen to function
Can be fuelled only carbohydrate
Produces ATP quickly but, in doing so, uses large quantities of glucose
Fatigues when lactic acid accumulates to high levels
Recovers in 30 minutes to one hour
The Aerobic System
The aerobic system :
 Supplies energy for moderate activity lasting
more than a few minutes
 Uses carbohydrate, fat and even protein as fuel
 Is extremely efficient in the production of
energy, allowing sustained work
 Has ability to spare glycogen and use fat to
conserve the premium fuel (carbohydrate)
 Is fatigued by the depletion of glycogen
 Produced carbon dioxide and water as byproducts
 Recovers slowly from strenuous work, but
quickly from light work
Questions
1.
Discuss the main differences between the three energy systems.
2.
Explain why some endurance athletes ‘hit the wall’ in the final stages of
a marathon.
3.
What strategies would you suggest to minimise the chance of this
happening?
4.
Estimate the energy system contributions for the following activities:
pole vault, tennis, a100-metre swim, hockey.
5.
Only two men in history have won the Olympic 400 metres and 800
metres double (in 1906 and 1976).
a. Critically analyse the following table and indicate why few athletes
compete in both the 400 metres and the 800 metres at Olympic
level.
b. If an athlete wanted to train for two events, what combination
would you recommend? Justify your recommendation.
6.
Using the Table, discuss:
a the energy system contribution to Michael Phelps’ eight events
b the fuel source for ATP production
c the recovery time required from each event. (Consider, for example, 13
August, when he swam two finals within 60 minutes, and 15 August, when
he had two races and a medal ceremony during the 35-minute break.)
Types of training and
training methods
• Training can be classified into four broad
types:
– aerobic
– flexibility
– anaerobic
– strength
Aerobic
• Programs will vary in mode, duration, frequency and
intensity, but all will involve the aerobic energy
system
• The mode of training refers to the type of activity—
swimming, rowing, cycling, running etc
• The duration of each training session will depend on
the exercise intensity and the fitness level of the
athlete. If training purely for health benefits, a
minimum of 20–30 minutes moderate exercise, five
days a week (frequency), is recommended.
• A more serious athlete may have 6–12 training
sessions per week to develop their aerobic base,
from 30 minutes to several hours duration for up to
four months.
• The mode of exercise will also influence the duration
of the sessions: training sessions in non-weight
bearing sports such as cycling, rowing and swimming
are able to be sustained for longer than sessions in
running, which involve a greater risk of injury.
• Training intensity, or effort, can be monitored by
using heart rate calculations - maximal heart rate.
Continuous training
• Continuous training means exercising non-stop for a
minimum of 20 minutes up to several hours. There
are two types of continuous training—long slow
distance, and high-intensity continuous.
• Long slow distance training is generally at a low
intensity equivalent to lactate transition 1 (LT1)—
previously referred to as the aerobic threshold
• high-intensity continuous training is in the lactate
transition 2 (LT2) training zone—previously
referred to as the anaerobic threshold
• Advantages of continuous training (running, cycling,
swimming, rowing) are that it:
– is time-efficient
– is easy to follow
– improves aerobic performance.
• This type of training does, however, have some
disadvantages:
– It is often performed at a lower intensity because of the
duration.
– It can be monotonous.
– It is not specific for team sport athletes.
Fartlek training
• Fartlek training involves continuous exercise
interspersed with ‘sprints’ of varying distances.
• The training session may involve a 30-minute run
with 15 sprints of 30–120 metres.
• Advantages of fartlek training compared to long slow
training include ;
– variety of pace,
– higher intensity of the training.
• disadvantages of fartlek training (like continuous
training),
– it is not sport-specific
– higher intensity may increase the risk of injury.
Interval training
• Interval training involves completing a number
of prescribed sessions of exercise, each
followed by a recovery period
Interval training is also
used by cyclists to
improve
their aerobic capacity
Circuit training
• Circuit training involves a series of exercises
that are performed one after the other, in a
‘circuit’, with limited (or no) rest between
exercises.
• Each exercise is called a station. Circuits can be
designed to improve strength, muscle
endurance, anaerobic fitness or aerobic
fitness, depending on how the specificity and
overload principles are applied.
• In order to design a circuit for aerobic effects,
research recommends the following
guidelines:
– Use lighter weights—less than 40 per cent of the
one-rep maximum (1RM) one-repetition maximum, is the maximum
load that can be lifted once.
– Extend the work period to 30–60 seconds.
– Select exercises that use large muscle groups.
– Intersperse aerobic activities (run, step-ups, bike,
skip) with resistance stations.
• Some advantages of incorporating circuits into
your training are that:
– you can cater for large numbers of participants
– workload is quantifiable (in terms of weight lifted
or repetitions performed)
– competition is indirect—each person can work to
their own capacity
– less fit participants feel less conspicuous
– you can provide a high volume of training in a
short amount of time.
Results of aerobic training
• Some of the physiological adaptations from
developing a strong aerobic base include:
– a higher maxVO2
– greater efficiency at carrying oxygen to the
working muscles, due to an enlarged heart
– increased blood volume
– increased utilisation of fat as an energy source
Anaerobic
• Intervals of short duration and high intensity
can be devised to target both anaerobic
energy systems (i.e. the alactacid and lactic
acid energy systems).
Athletes who compete in sprint
events, such as Anna Meares
(silver medallist in Beijing, 2008),
require high intensity anaerobic
training
• Changing the duration of the interval but
keeping the effort at 95–100 per cent of
maximal effort will alter the training effect
• For example:
–
–
–
–
up to 6 seconds: targets alactic power
6–25 seconds: improves alactic capacity
25–40 seconds: incorporates lactic power
40–60 seconds: improves lactic capacity.
• Recovery rates will be influenced by the
training status of the athlete
– Recovery rates of 2:6 are used to develop the anaerobic
energy system. For example, if the repetition is 15 seconds
in duration, a recovery of 30–90 seconds is needed.
Speed, acceleration and agility
• Speed, acceleration and agility are integral to
a range of sports.
• Maximum speed is often limited by the
athlete’s technique
• Speed training must be performed early in a
training session, before an athlete becomes
fatigued.
• The intensity of the repetitions should be
maximal while the total volume of the sprints
is kept to a minimum—that is, aim for quality,
not quantity.
• Repetitions will range from 20–60 metres at 95–100
per cent intensity.
• Speed cannot be improved if the athlete is only
expending 75–80 per cent effort.
• A full recovery is recommended between repetitions
(2–5 minutes).
• Acceleration, or speed off the mark, is important in
most team sports and needs to be trained specifically
•
The following repetitions are examples of acceleration training:
–
–
–
–
–
–
–
lie on stomach (head first) and sprint 15 metres
lie on back (feet first) and sprint 10 metres
lie on stomach, roll sideways and sprint 10 metres
a three-point start (one hand, two feet) and sprint 15 metres
six straight leg bounds and sprint 15 metres
ninety-degree jump turn to the left; return to the start and sprint 5 metres
medicine ball throw and sprint.
• Agility is the ability to rapidly change direction
without the loss of speed or balance.
• Agility or lateral speed involves decelerating,
adjusting stride pattern and body position,
and accelerating again
Power
• A powerful athlete is able to apply a large
degree of their maximal strength in a very
short period of time.
• The formula for power is:
force × distance
time
• No matter what method of training you use to
develop power, you are relying on the
anaerobic energy system.
Flexibility
• Flexibility is the ability to move a muscle
through a complete range of motion.
• The benefits of improved flexibility include:
•
•
•
•
•
•
•
less tension in muscles
increased relaxation
greater ease of movement and better coordination
increased range of motion (ROM) of the muscle/limb
preventing injury
better body awareness
less soreness in the muscle after other forms of
exercise.
• Different people have different levels of
flexibility.
• Factors that can influence a person’s flexibility
include their age, gender, level of physical
activity, temperature and joint structure.
• There are four main types of stretches that
can be included in a flexibility program:
– static stretching,
– dynamic stretching,
– ballistic stretching, and
– proprioceptive neuromuscular facilitation (PNF)
stretching.
• Static stretching - This is where the muscle is slowly taken to
the end of its range and held for a period of time. The stretch
may be held for 10–30 seconds.
• Dynamic stretching - involves progressively faster and
continuous movements where the muscle is gradually worked
to its full range of motion.
• Ballistic stretching - involves a bouncing action at the end of
the range of movement. This type of stretch has the greatest
risk of injury
• PNF stretching - involves a combination of contraction and
relaxation of the agonist muscles and antagonist muscles.
Generally a static stretch is followed by an isometric
contraction for approximately 10 seconds. The muscle is the
relaxed and followed by a greater stretch.
1 The athlete lies on her back with one leg
straight on the ground and the
other in the air.
2 Her partner holds her foot and slowly
pushes the leg back until the athlete
can feel a stretch in his hamstring.
3 The athlete then pushes against her
partner for a period of 5–10 seconds
and relaxes the muscle for 5 seconds.
4 The partner slowly increases the stretch,
talking to the athlete to determine
the range of stretching she is comfortable
with.
5 This is followed by another isometric
contraction.
PNF Stretching
Strength training (resistance
training)
• Resistance training has a number of health
benefits, such as changes in body composition
and fats, and increased core strength to
reduce lower back pain.
• Strength can be defined as the maximum
force generated in a single muscular
contraction.
Strength training
• Strength can be defined as the maximum force
generated in a single muscular contraction.
• Absolute strength is the load a person can lift on a
bench press in one repetition.
• Relative strength, on the other hand, takes into
account your body size. (If two athletes can lift
120 kilograms on a bench press, but one weighs
90 kilograms and the other weighs 80 kilograms,
the 80-kilogram athlete has the higher relative
strength.)
• Muscle hypertrophy refers to an increase in the
size of muscle fibres and the connective tissue
between the fibres. It occurs as a result of
strength or resistance training, and enables th
muscle to generate more power.
• Power, or speed strength, is the ability to
generate force quickly.
• Muscle endurance, or strength endurance, can be
defined as the ability of a muscle group to
perform a number of repetitions at a submaximal
load over a longer period of time.
• Weight training, body weight exercises, band
exercises and circuits can be used to increase
muscle endurance
Strength
Power
Hypertrophy
Muscular Endurance
Principles of training
• Effective and safe training programs are
based on six key principles of training:
Progressive overload
• A training stimulus that exceeds the level the
athlete has become accustomed to.
• Overload can be achieved by:
– increasing the intensity or resistance
– increasing the number of repetitions or sets (volume)
– increasing the duration of a repetition or overall
training session
– increasing the frequency of training
– decreasing the recovery periods between reps or sets
– changing the type of activity.
Specificity
• The body responds to the specific exercise that we
perform, so it is important that a training program
reflects what we want to improve in terms of energy
systems, muscles used, movement patterns, and skill
development.
– For example, if a person wants to improve their threepoint shots in basketball, they need to practice this shot in
a fatigued and non-fatigued state.
Reversibility
• Training adaptations only last for as long as training
continues.
• If an athlete stops training, they experience a
detraining effect, and begin to lose the physiological
adaptations they have gained.
– This is why you hear the saying ‘Use it or lose it’—it means
that the training benefits are reversible if training sessions
are missed.
Variety
• Completing the same training drills leads to
boredom and monotony for an athlete, and
may result in reduced training effort.
• It is important that coaches incorporate
change in any training program.
Training thresholds
• Training thresholds are the upper limits of a
training zone that will bring about improvement
in fitness. Graph
• LT1 (lactate transition 1)—the intensity or training
zone where lactate concentration is just above
resting values.
• LT2 (lactate transition 2) - this is where lactate
production is in equilibrium with lactate clearance
• In training zones T2 and T3, which have an
intensity of 75–90 per cent of maxHR or 60–83
per cent of maxVO2, fats and carbohydrates are
contributing to energy production.
• In the higher LT2 zone, there is a shift to
predominantly carbohydrates being used as the
energy source. This occurs at intensities that are
equivalent to 83–86 per cent of maxVO2, or 90–
92 per cent maxHR.
• To train anaerobic energy systems, an athlete
needs to be at the T6 threshold, which
corresponds to training intensities greater than
aerobic power (max VO2)
Training Thresholds
Warm up and cool down
• Warm-up activities prior to competition
and training can enhance performance,
increase range of motion and protect
against injury.
• At the end of a session, cool-down
exercises will also offer a range of benefits
to an athlete.
• Warming up
– For most sports, a general warm-up of 5–10 minutes
followed by a more specific warm-up for 10–15
minutes will prepare the athlete, both physically and
mentally, for the upcoming activity
– The specific component of the warm-up will simulate
aspects of the performance.
– Points to consider for warm-up design include:
• choice of exercises (specificity)
• volume and intensity of the warm-up
• time period from the end of the warm-up to the start of the
performance
• the level of performance of athletes.
Australian Opals
warm-up
• Cooling down
– At the conclusion of training or competition, a ‘cooldown’ or active recovery is recommended.
– This generally involves any mode of low-intensity (40–
50 per cent maxVO2) exercise.
– Benefits can include
• a decrease in blood lactate,
• a more gradual decline in body temperature and the reduced
likelihood of delayed-onset muscle soreness.
– The most commonly used cool-down involves a
combination of cardio exercise (such as jogging, cycling
or swimming) and stretching, and varies in duration
from 10 to 20 minutes.
Example of how the different training principles can be used to develop training sessions
Question
The friends wish to do a ‘moderate’ (65–85 per cent) run together. Assume
temperate weather conditions.
a Identify the speed they should be running.
b Identify the heart rate that should be achieved by each runner at that
pace.
• Identify five specific examples of how
progressive overload can be used in designing
circuit training.
• A high-school long jumper has a history of
hamstring injuries. Recent testing revealed his
hamstring strength is normal, although he
continues to experience hamstring tightness
and requires longer than usual to ’loosen up‘
before training.
a. Explain how this long jumper shoul prepare
for training, and outline a appropriate warmup.
b. Identify the types of stretches that are
appropriate after training.
Physiological adaptations
in response to training
• Physiological and metabolic adaptations occur
in response to an effective training program.
• With training, athletes are able to work longer
and faster before fatiguing than an untrained
person.
Resting heart rate
• Resting heart rate is the number of contractions your heart makes in 1
minute when at rest.
• An untrained person may have a resting heart rate of 70 beats per
minute, compared to an elite endurance athlete who may have a
resting heart rate of less than 40 beats per minute.
The effect of exercise on
maximal heart rate
Stroke volume:
the amount of blood pumped from the heart
(the left ventricle) per beat.
A trained person will have a higher
stroke volume at rest, during
submaximal exercise and during
maximal exercise than an untrained
person.
Aerobic training over a number of years
results in an increase in the size and
wall thickness (strength) of the left
ventricle, enabling more blood to be
pumped with each contraction.
•This adaptation is a main contributor to
the increased maximal cardiac output
of endurance athletes and their high
maxVO2
Cardiac Output:
The amount of blood pumped from the heart
per minute
Resting cardiac output is related
to body size and is approximately
5–6 litres for trained and
untrained people
During submaximal exercise of the same work rate,
there is very little difference in cardiac output between
the trained and untrained person
However, the trained person will be working more
efficiently—they are able to meet the blood flow demands
through their increased stroke volume and lower heart rate
compared to an untrained person.
The maximal cardiac output for endurance athletes can
be 30 litres per minute, or even higher, compared to
about 20 litres per minute for an untrained person.
Oxygen uptake and lung capacity
• Oxygen uptake is the amount of oxygen the body
uses in 1 minute.
• Aerobic training can increase a person’s maximal
oxygen uptake, or maxVO2, by 20–40 per cent.
• This is due to the increased cardiac output and
the body’s ability to extract more oxygen from the
muscles during exercise.
• Having a greater oxygen uptake means there is
more oxygen available for ATP production through
aerobic glycolysis.
During submaximal exercise, the trained
person reaches a steady state more rapidly
and has a smaller oxygen deficit for the
same exercise compared to the untrained
person.
Therefore a trained person who is less reliant
on anaerobic energy consumes a greater
amount of oxygen during this exercise.
Factors contributing to increased maxVO2 after endurance training
Lung capacity remains relatively unchanged with training.
There is a reduction in minute ventilation (volume of air inhaled
or exhaled in 1 minute) during submaximal exercise for
endurance trained athletes compared to pre-training levels.
The effects of endurance training on ventilation during submaximal exercise
Under maximal conditions, endurance athletes have recorded
minute ventilation readings of 180 litres per minute, compared to
120 litres per minute for untrained people
These adaptations may result in reduced fatigue of respiratory
muscles, while assisting the body in getting rid of carbon dioxide
during maximal exercise.
Haemoglobin level
• Endurance training increases the blood volume and
haemoglobin (Hb) levels in the body.
• Haemoglobin is the protein part of the red blood
cells that can carry oxygen.
• On average, males will have slightly higher Hb levels
than females.
• Training at altitude may increase a person’s Hb level
allowing more oxygen to be carried to the muscles.
Immediate Training Responses
Heart Rate is the number of times the heart
beats per minute
Stroke volume is the amount of blood ejected by
the left ventricle during contraction. It is
measure in mL/beat
Cardiac output is the amount of blood pumped
by the heart per minute
Lactate levels refers to the amount of lactic acid
that accumulates during intense anaerobic
activity
Ventilation rate is the depth and rate of
breathing and is expressed in breaths per
minute
Immediate Physiological
Response to Training
At Rest
Measure
Maximal
Untrained Trained Untrained
Exercise
Immediate
Trained
Response
Heart rate (beats
per minute)
72
50
180
175
Increases – the
higher the intensity,
the higher the heart
rate
Stroke volume
(mL/beat)
70
100
95
140
Increases
Cardiac output
(L/min)
5
5
17.1
24.5
Increases in line with
intensity of exercise
Lactate levels
(mmol/L)
1
1
9
16
Increase rapidly
during the anaerobic
phase of work
Ventilation rate
(breaths/min)
12
12
Variable
Variable
Increases. Will level
off as steady state is
reached
Aerobic Training – Key Terms
Resting heart rate refers to the number of beats per
minute while at rest
Stroke volume refers to the amount of blood ejected
by the left ventricle during a contraction. It is
measure in mL/beat
Cardiac output is the amount of blood pumped by
the heart per minute
Oxygen uptake is the ability of the working muscles
to use the oxygen being delivered
Lung capacity is the amount of air that the lungs can
hold
Haemoglobin is a substance in the blood that binds
oxygen and transports it around the body
Blood pressure is the pressure that the blood exerts
against the inner wall of the blood vessels
Physiological adaptations to
Aerobic Training
Resting heart rate
Average is 72bpm. Lower with training
Stroke volume
Big increase in trained athletes from rest to maximal
exercise
Cardiac output
Much bigger in trained athletes at maximal exercise
(up to 30 litres/minute higher)
Oxygen uptake
Much higher in trained athletes (readings usually of 75
mL/kg/min or higher)
Lung capacity
Little change
Haemoglobin levels
Big increase. Altitude training further increases
haemoglobin levels
Blood pressure
Both systolic and diastolic are lowered in the long
term
Muscle hypertrophy
• Muscle hypertrophy occurs when both the
muscle fibre size and the connective tissue
between the fibres increase as a result of
resistance training.
• This enables the muscle to generate more
force and power.
Effect on fast/slow twitch muscle fibres
Training causes a number of changes within the
muscle. Resistance training increases the ATP, PC
and glycogen stores in fast twitch muscle fibres.
Resulting in improved anaerobic performance.
Enzyme activity also increases with resistance and
aerobic training, resulting in enhanced ATP
production.
Resistance training also increases force, as more
muscle fibres contract at the one time.
Fast twitch muscle fibres
are muscle fibres that do not use
oxygen to create fuel and are best
utilised for short
bursts of speed and strength; they
are also known as Type 2 fibres.
Aerobic training enhances the muscle fibres’ ability to use fatty
acids as an energy source. So when exercising at a
submaximal level, the glycogen stores are being spared which
will delay the onset of fatigue.
Glycogen stores also increase as a result of aerobic training.
The number of capillaries and mitochondria in muscles
also increases with aerobic training, enhancing carbon
dioxide removal and oxygen delivery from and to
muscle fibres. Muscles are also able to send lactate to
the liver to be used as another energy source.
Low-intensity training will predominantly use slow twitch fibres (Type
1), so higher intensity exercise is needed to recruit fast twitch fibres
and stimulate adaptations in them.
1. Is the oxygen deficit larger or smaller for an
aerobically trained person compared to an
untrained person? Justify your answer.
2. Explain the cause of a triathlete’s larger cardiac
output compared to an untrained individual.
3. Identify the factors that account for greater
oxygen extraction in endurance athletes.
4. Outline the physiological adaptations that occur
as a result of resistance training.
5. Analyse why there is an improvement in beep test
results (maxVO2) among Year 10 students after
10 weeks of aerobic training.