Transcript BIOMECHANICS

BIOMECHANICS
Biomechanics is the study of forces and their
effects on the human body during movement.
Forces are the basis for all movement.
CENTRE OF GRAVITY
 The point at which all parts of an object are
equally balanced.
 Standing up right our centre of gravity is
around our navel.
 The centre of gravity changes depending
upon what position the body is in.
 The centre of gravity can lie outside an
object.
 Generally, the lower the COG the more
stable an object will be.
LINE OF GRAVITY
 The vertical line that passes through the
centre of gravity to the ground.
 The line of gravity is important when
determining the stability of an object.
 If the line of gravity falls within an object’s
base of support the object is relatively
stable (and vice versa).
BASE OF SUPPORT
 The area within an object’s point of
contact with the ground.
 Generally, the larger the area the base of
support covers, the more stable an object
will be.
QUESTIONS
 Copy each of the
objects and draw in
the centre of gravity.
 Which player is more
stable? Explain using
the words base of
support, line of gravity
and COG.
BIOMECHANICS - MOTION
 Linear motion – is in a straight (vertical) line.
All parts of the body move in the same
direction and at the same speed. [Give
examples]
 Angular motion – occurs around an axis. This
can be internal (body parts rotating around a
joint) or external e.g. ………..
 General motion – a combination of linear and
angular. This is the most common of all
movements, as most human movement
requires rotation of body parts around joints
e.g. ……….
BODY TYPES
 ECTOMORPHS
 Typically tall and slender. They don’t have
much muscle and typically little fat.
 Relatively long arms and legs. This allows
them to reach further, which gives an
advantage when contesting the ball in netball
and basketball.
 Typically suited to endurance sports and
sports that don’t require a lot of physical
contact.
BODY TYPES
 ENDOMORPHS
 This body type tends to be shorter and
carries large amounts of fat compared
with ectomorphs.
 Extra body fat allows them to float better
in the water and provides insulation from
the cold.
 Suited to short duration activities not
requiring lots of endurance.
BODY TYPES




MESOMORPH
Carries a large amount of muscle.
People with this body type look athletic.
Suited to activities requiring strength and
endurance, as the extra muscle provides
the power to perform activities faster and
for longer periods of time.
Identify Each of the Body
Types
Endomorph
Ectomorph
Mesomorph
Newton’s Laws of Motion
 Law 1: A body continues in its state of
rest or uniform motion unless an
unbalanced force acts upon it.
 An object at rest tends to remain at rest
unless acted upon by some external
force.
Inertia
 The body’s tendency to remain at rest.
 The greater the mass of the body, the
greater the inertia.
 Which object has greater inertia, a ping
pong ball or shot?
 This directly relates to Newton’s 1st Law.
How?
Newton’s Laws of Motion
 Newton’s 1st Law
illustrated.
Newton’s Laws of Motion
 Law 2: The acceleration
of an object is directly
proportional to the force
causing it, is in the same
direction as the force,
and is inversely
proportional to the mass
of the object.
 When a force acts upon
a mass, the result is
acceleration of that
mass.
Newton’s Laws of Motion
 Law 3: Whenever a
force is applied there
is an equal and
opposite reaction.
BIOMECHANICS
FORCE SUMMATION
 Many skills performed in sport
require maximum speed or force
to be generated.
 Some skills require maximum
force to get a result, while others
require maximum speed or
velocity.
 In order to do this, an athlete
needs to involve as many body
parts as is technically possible.
 The movements occur at
relatively the same time but in
the correct order.
 The more body segments
involved the greater the force
or speed generated.
EXAMPLE
 An athlete competing
in a discuss
competition would
generate less force
and therefore less
horizontal distance, if
only the arm and
shoulder are used.
 Another competitor
using force built up
from using legs, hips,
back, shoulder, arm
and wrist in order
would throw further.
SUMMATION OF FORCES
 Maximum speed is achieved by adding
the speed of each segment and
transferring this to the final part of the
body.
 The speed of the last part of the body at
the moment of contact or release will
determine the velocity of the implement
or projectile.
 When serving in tennis or hitting a tee
shot in golf, at the end of the movement of
body segments, the accumulated speed
should be transferred to the racquet or
club to generate maximum speed or
force.
WORKING EXAMPLE OF
FORCE SUMMATION
 The student is unable to produce
enough force to propel the
basketball to the basket.
 A solution maybe the students
awareness of force summation.
 Eg: When performing the
basketball set shot it is important
that the body parts move
sequentially.
 Force summation is the ability to
use all body segments involved to
generate greater force or speed.
 Firstly the basketball player needs a
stable base from which to execute
their shot.
 The knees must flex then move to
extension in order to start the
movement.
 The muscles involved in this
actions are the hamstrings and the
quadriceps.
 The hamstrings initiate flexion
followed by the quadriceps being
the prime movers for the knee
extension.
 This movement continues with
shoulder extension, elbow
flexion and wrist extension.
This moves to shoulder flexion,
elbow extension and wrist
flexion( prime movers included
here? )
 The end result is a more
powerful force that can be
transferred to the ball so that it
travels as far as it can towards
the rim.
PROJECTILE MOTION
FACTORS AFFECTING
PROJECTILE MOTION
 Any object
released into the
air is termed a
projectile.
 The flight path of a
projectile consists
of a vertical and
horizontal
component.
 What does this
mean?

Regardless of
the type of
object that is
being released,
or by what
means it is
being
projected, they
are all
governed by
the same
principles.
1. Gravity.
2. Air resistance.
3. Speed of
release.
4. Angle of
release.
5. Height of
release.
6. Spin.
GRAVITY
 Gravity acts on a body to give it
mass. The greater the weight of an
object the greater the influence of
gravity upon it.
 What is the effect of gravity on a
projectile?
AIR RESISTANCE

1.
2.
3.
4.
There are several key factors that bring
air resistance into play.
The larger the surface area, the more
air resistance will affect the object.
If the surface is rough then air
resistance will be greater.
Speed. As speed increases, so does air
resistance. (Think of the space shuttle)
Mass. The smaller the mass (lighter the
object) the more air resistance will
affect it.
Speed of release.
 Generally, the greater the speed of
release, the greater the distance gained.
 In many game situations this is a factor
that must be under constant control.
 Can you give me an example?
ANGLE OF RELEASE
 For any given speed of release, the
optimum angle of release is always 45
degrees.
 Is this the case in many sports? Why?
 What would happen if the angle of
release were to high for a given activity?
 Poor distance gained
 What would happen if the angle of
release were too low for a given activity
 Poor flight time and possibly poor
distance.
Height of release
 The interrelationship
between height of
release and angle
of release is
important to
consider.
 Have you ever
noticed that tall
basketball players
shoot the ball at a
lower angle than
short players.
The reason behind this can be
summarized as follows
1. As the height of release
increases, the angle of
release decreases.
2. As the height of release
decreases, the angle of
release increases.
3. THINK ABOUT IT!
SPIN
 Consider a game of Tennis. What
happens to the distance achieved with a
topspin shot compared to one with
backspin?
 A topspin shot gives poorer distance
compared to backspin.
SOOOO……..

This leads us to the following
two principles with respect
to projectiles and spin.
1. Range is decreased with
topspin.
2. Range is increased with
backspin.
 WHY?
Practical Example
 Question?
 How is this biomechanical
principle applied to the
overhead serve in volleyball.
Where can I see this being
applied?
ANSWER.
 Firstly the speed or the force
that the ball is struck/released
at is important. The speed at
which the ball is struck will
determine how far the ball
will travel. The striking force
must be sufficient enough to
allow the ball to cross the net
but not enough to mean the
ball goes out of play.
 The height of release also
influences the horizontal distance
covered, too high and the ball may
go to far, too low and the ball may
strike the net. The angle is also
important in conjunction with this.
The angle and height of release
must be judged correctly in order
that the serve is successful. Spin
can also be applied in order to
make the ball dip after the netmaking it harder for teams to
return.
levers
A lever is used when you want to apply
more force.

Most levers have three clearly
identified parts:
1. THE FULCRUM
The pivot point around which the
movement happens. In the body this is
usually the joint.
2.THE LOAD
The weight that needs to be moved.
3.THE FORCE
The place where the force is applied. In
the body this is the effort produced by
the muscles contracting .

CLASSES OF LEVER
There are
three classes
of lever.
 Not
surprisingly
they are
called:
1. FIRST CLASS
2. SECOND CLASS
3. THIRD CLASS

 First class levers can help to
either increase force or
generate more speed
depending on the position of
the fulcrum.
 Second class levers allow more
force to be produced because
the effort ,or force arm ,is
longer than the resistance arm.
 Third class levers generate
speed rather than force.
LEVERS IN SPORT
 In many sports the equipment you use
act as an extension of the levers in your
body and helps to generate greater force
or sped. Two good examples of levers
used in sport can be seen in rowing or
golf.
LEVERS
 A lever is used when you want to apply more
force. Most levers have three clearly identified
parts:
1. The fulcrum – the pivot point around which
the movement happens. In body levers this is
usually the joint.
2. The load – the weight that needs to be moved
(resistance).
3. The force – the place where force is applied.
In the body this is the effort produced by the
muscles contracting.
LEVERS
 Can you think of any household
tools/machinery that act as levers?
Levers in Sport
 In some sports the equipment you use acts
as an extension of the levers in your body
and helps to generate greater force or
speed.
 Give some examples of levers in sport.
 Longer levers result in more speed,
beneficial for striking and throwing objects.
 Shorter levers result in greater strength,
beneficial for pushing, pulling, and lifting
objects.