The Muscular System (2)
Structure of muscle
 Muscles are made up
of many muscle
fibres, each of which
contain many
myofibrils.
 These can either be
slow twitch or fast
twitch.
Types of Muscle Fibre
 Slow twitch (Oxidative) Fibres



Deep red in colour
Have a good Oxygen supply
They contract slowly, but can work for long periods
of time without tiring.
 Fast twitch (Glycolytic) Fibres


White in colour
A more forceful contraction, but fatigue relatively
quickly.
Muscle Tone
 Muscle cells are never all resting at the same time.
 Some are muscles are always ready for action – this
is known as muscle tone.
 One of the functions of muscle tone is that it keeps
the body primed and ready for instant action.

Also keeps the body in an upright position
 This is called POSTURE
 Our joints are held firm by the flexor and extensor
muscles both working at the same time
Exercise & the Muscular
system
 What are the immediate effects of exercise
on the muscular system?




Exercise increases the body’s demand for Oxygen
and glycogen as the muscles need more fuel to
function.
Extra waste products are created, and extra blood
needs to be pumped around the body to take these
away.
Aerobic exercise can continue for a sustained period
of time as the intensity is relatively low.
High intensity exercise will result in the production of
lactic acid, if this builds up then exercise will cease
as muscles begin to ache and possibly cramp
What are the long term effects
of exercise?
Increased muscle size: Hypertrophy



Training using the principle of progressive
overload, applies stress to the skeletal muscles.
This results in them being damaged as the
muscle fibres are pulled apart causing trauma.
The body rebuilds bridges between muscle
fibres, and actually makes them slightly
stronger
 This requires up to 48 hours.
Anabolic Steroids
 Most common drugs used to enhance sports performance.

Testosterone, stanozonal, nandrolone and bodlenone.
Anabolic steroids
 Mimic the male hormone testosterone
Increase muscle mass and develop
bone growth.
 Therefore increase strength
 Also allow you to train harder.
 Increases aggression
 Side effects
 Deepen the voice & cause the
growth of facial hair.
 Mood swings and aggression
 Increased risk of CHD’s.

Bad Posture
 It is important that our bodies remain
balanced.


However we often allow our bodies to
stoop or sag
This causes weight to be unevenly
distributed and some muscles are required
to carry extra weight.
 If
they are weak they will soon become tired.
 Continual bad posture can lead to long
term deformity of the spinal column.
Factors contributing to bad
posture
 Working long hours slouching over a
desk
 Poorly fitting shoes/high heels
 Poor muscle tone
 Poor flexibility
 Weak muscles in the lower back, legs
and the abdominal muscles.
 Overweight.
Curvature of the spine
 Lordosis


Causes lower back
problems, leading to
pain.
Weak abdominals
and gluteus maximus
muscles can add to
these problems.
Curvature of the spine
 Kyfosis



Sometimes described as ‘hump
back’
This is an excessive outwards
curvature or flexion in the upper
back.
This is often due to weak adductor
muscles in the shoulder region
Curvature of the spine
 Scoliosis

This is a condition in which there
is lateral curvature of the spine,
which can be observed with an
x-ray
Good vs Bad posture
Improving or maintaining good
posture
 Strength work


Strength exercises
Weight training
 Heavy weights are not needed

Correct lifting technique helps achieve and
maintain good posture
 Flexibility

Will help to produce an athlete or individual
with improved body shape
Potential injuries
 Atrophy
Loss of muscle mass & strength due to stopping
training.
 Soft tissue injuries
 Include tears, pulls & strains
 Small muscle fibres may be torn from their attachment to a
tendon
 During intense competition muscle
fibres contract & relax very
quickly, & this can cause
connective tissue & the blood
vessels which run inside them to
be torn.

Task
 Why do we warm up & cool down?
 What should be included in a warm up?
 Design an appropriate warm up for one
of your chosen sports.