Aerobic capacity
For the four main components of fitness you will be expected to
know the following:
- Definition of component.
- Factors affecting the component.
- Tests for that component.
- Methods of training - to improve the component.
- Adaptations resulting from training.
- Be able to describe the energy system(s) and fuel used.
Definition of aerobic capacity
The ability to take in, transport and use oxygen to sustain prolonged
periods of aerobic work.
Factors affecting aerobic capacity
Body systems
Respiratory systems ability to consume(take in) oxygen.
Cardiac systems ability to transport oxygen.
Vascular systems ability to transport oxygen.
Muscle cells ability to use oxygen.
Heredity
Your genes will have a large say in your aerobic capacity/VO2 max.
This helps to explain the great variation that we see in aerobic
capacity. Why some people struggle to jog half a mile, whilst others
can run for fun!
Some people are born with the physiology that gives them the
potential to have a high VO2 max such as a high proportion of slow
twitch muscle fibres (Type 1)
Individual response to training - because of their genetics some
individuals will respond much quicker and show a greater
improvement, benefiting from the adaptations that take place.
Remember - genes will only take you so far – training is needed to
maximise the potential.
Training
A programme of aerobic training will increase VO2 max/aerobic
capacity due to the adaptations that take place.
See adaptations later.
Age
As we get older our VO2 max declines as our body systems become
less efficient. Approx 1% decline per year (10% per decade).
CV system decline:
- Max heart rate decreases (5-7 beats/min per decade)
- Cardiac output/stroke volume/blood transportation to muscle
tissue decreases mainly due to weakening of contraction of left
ventricle and elasticity of cardiac and vascular tissue (heart
and arteries/arterioles)
Respiratory system decline:
- Decrease in maximum ventilation – both vital capacity and
minute ventilation is reduced. This again decreases linearly-in
other words, year by year. This is due to the decrease in
elasticity of the lung tissue and respiratory muscle. There is
also a decrease in contractile strength of the respiratory
muscles.
Part of the reason for the decline of VO2 max is due to a decrease
in activity levels. Therefore:
Continued aerobic activity/training as you get older will
maintain/slow down the decline in VO2 max.
Gender
VO2 max values are generally 20-25% less for women than men.
This is mainly due to:
Smaller body size– smaller lung size (O2 intake/external respiration)
Smaller left ventricle – lower stroke volume and cardiac output at
max work rates.
Lower blood volume – less haemoglobin (less O2 carrying capacity).
Women are also disadvantaged by carrying a greater % of body fat –
lowering their VO2 max per Kg of body mass.
Aerobic capacity tests
There are two types of tests:
Indirect or predictive tests – these estimate or predict a VO2 max
based on the results of the test.
Direct test – these are accurate tests which directly measure the
oxygen consumption and usage.
PWC 170 test
This is an indirect (predicted) test
It is sub-maximal performed on a cycle ergometer.
Three progressive low to moderate work intensities are performed.
Intensity 1 – 100-115 Beats per minute
Intensity 2 - 115-130 bpm
Intensity 3 - 130-145 bpm
Heart rates are recorded at each level.
Heart rate increases in a linearly with work intensity. This allows a
line to be drawn on a graph , through the 3 points (heart rate
readings) continuing until the heart rate 170 is reached on the
graph. This predicts the individuals work intensity when the HR of
170 bpm was reached.
The figure 170bpm was chosen as approximately the anaerobic
threshold.
Multi-stage fitness test
This is an indirect (predicted) test.
It is a progressive maximal test.
It involves a 20m shuttle run.
The 20m run is timed by a beep, which progressively becomes
shorter after each level (10-12 shuttle runs).
The test when the athlete fails to keep up with two successive
beeps or drops out.
This provides a level and a shuttle number e.g. 12.4. The score is
then compared with standardised tables to estimate/predict VO2
max for male and females.
Gas analysis test (such as the Douglas bag)
This is a direct test measuring accurately VO2 max.
It is the most valid and accurate method.
It involves wearing a mask that measures the oxygen in the air
breathed into the lungs comparing it to the measured oxygen being
breathed out. The difference between the two figures is the
consumed oxygen.
The test is progressive and is usually performed on a treadmill or
cycle ergometer. ( It is possible with the right equipment to perform
the test on a swimmer whilst swimming!)
As the test progressively becomes more difficult e.g. on a treadmill
the athlete runs faster, the O2 measurement whilst breathing out
becomes less and less. This continues until the O2 level in the
expired air remains the same as the previous level. This indicates
that the body can not use any more of the O2 - so have reached
their VO2 max. The athlete will finish the test working
anaerobically, in a near exhaustive state.
The equipment needed is expensive so this method of testing is only
practical with elite athletes.
Methods of training
There are three methods of training that will improve aerobic
capacity.
Continuous training
Repitition training
Fartlek training
Interval training
Whichever training method is to be used it is important that we
overload the system at the appropriate intensity to ensure
adaptations take place.
By measuring the intensity of the activity we can ensure that we are
within the correct training zone.
The most practical method of measuring training intensity is by
using target heart rates.
We looked at H.R. training zones in GCSE. This is similar in principle,
but uses a more complicated equation. Our training zones will be a
percentage of our maximum H.R. This is also known as the Critical
Threshold (CT)
Karvonen principle
220-age =max HR
CT = Resting HR + %( max HR – resting HR)
e.g. For a 17 year old with a resting HR value of 72 bpm.
We will do the equation based on 60% of max HR (remember at
GCSE we used the figures 60 – 80% of max HR to signify the
aerobic training zone)
CT = 72 + (0.6 x 131)
( to explain 220 – 17 =203 so 203-72=131
CT = 72 + 79 = 151
CT = 151 bpm
This would be a suggested HR for aerobic training for this individual.
Working between 60 and 80% is a good guide for the aerobic
training zone allowing for adaptations to take place.
The closer to the top end of the training zone will bring about
greater adaptations.
Training should be for at least 20-30 mins a minimum of three times
a week.
Intensity will depend on the requirements and fitness levels of the
individual. Training will be different for a top aerobic athlete than a
previously sedentary less fit individual.
Continuous training
Steady state, sub- maximal work (typically running, cycling,
swimming, rowing).
Prolonged period of time – minimum 20-30 mins.
HR should be above the Critical Threshold – 55 - 60% of max (using
the Karvonen method).
The % will change depending on the individual up to approx 80%. Top
aerobic athletes could work at a higher % and still remain working
aerobically (under the anaerobic threshold)
Most suitable for long distance athletes who work predominantly
within the aerobic system.
Fartlek training (Swedish for speed play)
Fartlek training involves varying the pace of the training (from a
slow jog to a sprint), changing the intensity of the training. The
athlete will move between working aerobically and anaerobically.
The terrain could change in terms of the ground state –
tarmac/grass/sand; to the gradient – flat ground to steep hills.
HR must remain over the Critical Threshold but will probably cross
over the anaerobic threshold, so the athlete works within both the
aerobic and anaerobic training zones.
Ideal for activities where the athlete continuously changes work
intensity such as team sports.
Will develop VO2 max and the recovery process (so important for
team sport players to recover quickly from intense work.
Interval training (repetition training)
Interval training involves combining periods of work with periods of
rest or recovery (relief).
This training method can be adapted for the specific needs of the
individual or the sport, by adjusting the four components that
interval training must contain:
- Work duration/distance - e.g. 3-4 mins or 1000m
- Work intensity – e.g.HR % or hill work.
- Rest/recovery/relief duration – increase time/decrease time;
is the recovery active or passive (e.g. static or jogging).
- Number of reps or work/relief intervals e.g. 2 x 2000m with
800m slow jog recovery / 4 x 100m with a 400m jog recovery.
Interval training sessions are often described as having a
work/relief ratio. This refers to the amount of work in relation to
the amount of recovery, e.g. 2:1 describes a session where the
work interval is twice as long as the recovery interval.
Aerobic interval sessions tend to have a higher ratio of work
intervals compared to rest. As a result there tend to be less
work/relief intervals (reps).
Anaerobic interval sessions on the other hand tend to relief interval
compared to the work interval, e.g. 1:3+. This allows for fuller
recovery after very high intensity work. As a result the number of
work/relief intervals (reps) will be higher.
The advantage of interval training is its adaptability to all training
needs. It also allows for greater intensity in work rate when
compared to continuous training as it allows for some recovery.
See examples of interval sessions in table form on p417 of textbook.
Energy system and food fuels used during aerobic work
Although ATP and PC are the fuels used at the very beginning of any
activity whether anaerobic or aerobic, the main fuels used for
aerobic activity are glycogen (glucose) or Free Fatty Acids (FFAs).
The fuels are used to provide energy for the re-synthesis of ATP.
They are broken down through the Aerobic system – You should be
familiar with this!
3 stages:
- Aerobic glycolysis
- Kreb’s cycle
- ETC
Glycogen and FFAs provide the energy for aerobic activity, which
one varies depending on a number of factors:
- Duration and intensity of activity.
- Availability of glycogen and FFAs.
Glycogen is the main fuel for the first 20-40 mins of exercise.
A greater amount of fats are broken down after 20-45 mins.
Fats become the main fuel at this time as glycogen stores become
depleted.
After approx 2 hours fats become the only fuel source as the
glycogen is almost totally depleted.
If during the activity intensity rises to a point where OBLA occurs,
the fuel source will switch to glycogen as fats cannot be broken
down anaerobically.
After a period of aerobic training the body adapts. FFAs become
the main fuel source of energy production. This is known as glycogen
sparing. This ‘saves’ the glycogen for use later in the activity, if
required.
Adaptations
This potentially a large mark question. It contains a lot of content
from last year’s work :
Cardiac/vascular/respiratory/muscular/skeletal systems.
The best way of answering an adaptations question on aerobic
capacity is to divide the adaptations into the different body
systems listed above.
In addition to these there will be adaptations under the heading –
healthy lifestyle e.g. reduced body fat.
These are listed and explained in table form in your textbooks on
p419-421 or p189-192 in the revision guide.
Rather than me writing these out, I’ll give this job to you !!
Practice listing these under their headings – with a quick explanation
of their benefit to the system which leads to the increase in aerobic
capacity/VO2 max.