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Fitness can be
Endurance
Flexibility
Strength
Speed
What happens when the
muscle contracts.
The skeletal frame is covered with
approximately 600 muscles, which
represent about 40% of the body’s
weight.
A muscle is a collection of long fibres
made up of cells and grouped in
bundles. Each bundle is separately
wrapped in a sheath that holds it
together.
This is further sub-divided into actin and
myosin filaments.
Stimulation of a muscle
Muscles work like engines by burning fuel to
produce movement.
They are energy converters, changing the
chemical energy in the food we eat into the
energy of movement (kinetic energy).
When the brain stimulates a muscle to
contract, a ready source of energy is required
to provide the fuel necessary to perform the
contraction.
Types of muscle
There are two distinct mixture of fibres,
which are two distinct types: fast-twitch
which is the quick sprint type and the
longer running cruising type for long
distance known as the slow-twitch fibre.
A fast-twitch muscle fibre is like the
engine of a sprint-type racing car. It can
produce high speed movement for short
periods of time.
Fast-twitch (Anaerobic)
The fast twitch needs a premium fuel
(carbohydrate) and produces a large
amount of waste- lactic acid because it
doesn’t burn up completely. The high
level of lactic acid, together with the
limited supply of fuel, means that a
sportsperson can never use these fast
twitch fibres for very long. Build up of
lactic will impair action.
Slow-twitch (Aerobic)
The slow-twitch muscle fibre is like the
engine of a touring car. It produces less
power, which means less speed; but it
can run for much longer periods at this
cruising speed.
It gets by on a lower grade fuel, a
mixture of fat and carbohydrate. The
fuel is more completely burned and the
Co2 is easier to handle.
Cardiovascular Fitness
The contraction of muscle requires
energy and in a race the athletes will
use up quite an amount of energy.
The energy comes from the oxidation of
foodstuffs.
Digested foodstuffs combine with o2 to
produce co2 and water and energy is
released.
Vigorous Physical
Activity
Energy becomes available to the
muscles if foodstuffs and o2 are
supplied to it.
In the course of vigorous activity like
a race o2 has to be taken to the
muscles while the activity is in
progress.
Bronchus
The bronchi are the tubes
which carry air from the
trachea to the inner
recesses of the lungs
where it can transfer
oxygen to the blood in
small air sacs called alveoli
Oxygen-food –energyco2 water
Oxygen is taken to the
muscles by the
cardiorespiratory system.
It is responsible for
supplying oxygen to the
blood and expelling waste
gases of which Co2 is a
major constituent.
Blood
How the blood carries
o2
O2 is carried in the blood stream by the
Haemoglobin in the red blood cells
Blood contains 44% red blood cells.
Erthrocytes
This may be reduced by disease or the
lack of iron in the diet, which means that
not as much 02 can be transported around
the body.
50% red blood cells: E.P.O. (Erythropoietin
Interior of the Heart
It is the efficiency of the heart which
determines the performance of an
athlete in an event lasting longer
than a few seconds.
Trained athletes tend to have larger
hearts.
How athletes and non
athletes differ
The size of the heart in the athlete is
larger.
Trained athletes tend to have a greater
number of red blood cells.
The athlete tends to have a greater stroke
volume than the non athlete.
Trained athletes tend to have a resting
heart rate of 40-50 beats per minute.
Untrained athletes tend to have a resting
heart rate of 70-80 beats per minute.
More enzymes present in an athlete.
Measuring
Cardiovascular Fitness
The cardiovascular fitness of an athlete
can be assessed by measuring how
much 02 an athlete can pump round his
body in one minute.
This is known as the Maximum oxygen
intake or V02 max.
V02 max of various
athletes
Cross country skiers: 6 litres of o2 per
minute.
1500 Metre runners: 5 litres per minute.
Untrained subjects have values of 3
litres per minute.