Download Physiological Adaptations in Response to Training

Physiological Adaptations in
Response to Training
Examine the relationship between
the principles of training,
physiological adaptations and
improved performance.
In response to training the body makes adaptations or
adjustments to the level of stress imposed on it.
These adaptations allow the body to function more
comfortably at existing levels of stress and respond
more efficiently to new levels of stress.
Although progressive improvements can be seen
throughout a training program, it usually takes
around 12 weeks to realise the entire benefits.
Training will cause adaptation to a number of
capacities including, resting heart rate, stroke
volume, cardiac output, oxygen uptake, lung
capacity, haemoglobin level, muscle hypertrophy
and effect slow and fast twitch muscle fibres.
Resting Heart Rate
Aerobic training causes a lowering of the resting
heart rate. This is because of the improved
efficiency of the cardiovascular system. An
untrained resting heart rate is usually between
70 and 90 beats per minute. Trained athletes can
have a resting heart rate as low as 30 beats per
minute.
Stroke Volume
Stroke volume increases as a result of aerobic
training. It refers to the amount of blood ejected by
the left ventricle of the heart during a contraction. It
is measured in mL/beat. Untrained people may have
a stroke volume of 70-80ml, while people involved
in aerobic training may have a stroke volume of 90125ml. This occurs because a trained athlete has a
stronger heart muscle, capable of a more forceful
contraction and an increase in the capacity of the
left ventricle, enabling more blood to be pumped out
in each contraction.
Cardiac Output
Cardiac output is the amount of blood pumped by the
heart per a minute. It is determined by multiplying
heart rate and stroke volume.
The cardiac output of a trained athlete may be similar
to an untrained person at rest, but during exercise
the cardiac output of the trained athlete will be
greater. An untrained person may have a cardiac
output of 15 to 20 litres per a minute while a trained
person may have 20 to 25 litres per a minute. In
highly trained endurance athletes, cardiac output
may even rise as high as 40 litres per a minute.
Oxygen Uptake
• Oxygen uptake (VO2) is the amount of oxygen that is
consumed by the mitochondria in the cells in order to produce
aerobic energy. Maximal oxygen uptake (VO2max) is the
maximum amount of oxygen that the body can take in and
utilise for production of aerobic energy. It is used to measure
cardiorespiratory fitness. A person’s VO2max is determined
by factors such as:
• Heredity
• Age - VO2max increases until the mid twenties and declines
thereafter.
• Gender - males generally have higher VO2max levels due to
increased muscle percentages and haemoglobin levels.
• Training Status - VO2max increases in response to aerobic
training.
Lung Capacity
• Lung capacity is the total amount of oxygen that an
individual’s lungs can hold. Lung capacity remains
relatively unchanged with most training programs,
but may improve slightly with maximal training.
Training can improve a person’s vital capacity i.e.
the amount of air that can be breathed in and out
during a single breath. Vital capacity is different to
lung capacity due to the fact that there is always air
left in the lungs, even after the most forceful
expiration. This leftover air is called residual
volume.
• The total lung capacity is about 6000mL in males
and slightly less in females due to their smaller size.
Haemoglobin Level
• Haemoglobin is found in red blood cells. Each red blood
cell contains 250 million haemoglobin molecules. He
average male has 14.3 grams of haemoglobin per 100mL
of blood, while the average female has 13.9 grams per
100mL of blood. Women's lower haemoglobin levels
contribute to lower VO2 max values. Haemoglobin is
essential as it binds to oxygen, enabling transportation
via the circulatory system as oxygen does not dissolve
easily in fluids of the body, if haemoglobin was not
present in the body we would require 80 litres of blood
to transport enough oxygen to live. Haemoglobin levels
can improve by up to 20% as a result of aerobic training.
Muscle Hypertrophy
• This term defines the process of muscle enlargement
and strength gains in response to resistance
training. Training does not increase the number of
muscle fibres, rather the size of the fibres. While
length of muscles remains the unchanged, the size of
the muscle becomes larger as an increase in its mass
and cross-sectional area. Hypertrophy is induced by
training programs that stimulate activity in muscle
fibres causing them to grow. Without stimulation,
muscle fibres can reduce in size, a condition known
as muscular atrophy.
Effect on Fast and Slow Twitch Muscle
Fibres
• Please write the following in your exercise book and make a reference to this
notes in your green activity booklets for future study purposes.
• Slow twitch muscle fibres or type 1 fibres which are red in colour contract slowly and for
long periods of time. The are recruited for endurance-type activities such as marathons.
• Fast twitch muscle fibres or type 2 fibres are white in colour and reach peak tension
quickly and are recruited for power and explosive movements such as throwing, sprinting
and lifting.
• Most people have approximately even numbers of slow and fast twitch muscle fibres,
however some individuals genetically have higher proportions of one type or the other.
• Physiological adaptation occur to this type of muscle fibre when they are subjected to
training that is specific to their role.
Effect on Fast and Slow Twitch Muscle
Fibres cont.
Aerobic training causes the following adaptations to occur in slow
twitch fibres:
• Hypertrophy of slow twitch muscle fibres.
• Capillary growth of up to an increase of 15% surrounding muscle
fibres to increase gaseous exchange and the removal of waste
products.
• Mitochondrial function. An increase in the number of
mitochondria cells as well as an increase in their size and efficiency
in utilising oxygen to produce ATP.
• Myoglobin content. Myoglobin is responsible for transporting
oxygen from the cell membrane to the mitochondria and storing it
for use when necessary. Endurance training can increase myoglobin
content by up to 80%.
• Oxidative enzymes. Increase in levels of activity making the
production of energy more efficient.
Effect on Fast and Slow Twitch Muscle
Fibres cont.
Anaerobic training causes the following adaptations to
occur in fast twitch fibres:
• ATP/PC supply. Fuel supply and the efficiency with
which fuel is used increases.
• Glycolytic enzymes. These increase, improving the
functioning within cells.
• Hypertrophy. This has the potential to increase
considerably and is dependant on the type, frequency
and intensity of training.
• Lactic acid tolerance. Training increases the ability of
fast twitch fibres to tolerate lactic acid, allowing
anaerobic performance to be sustained for longer
periods of time.