Chapter 9 Biomechanics and Sports

CHAPTER 9
BIOMECHANICS
AND
SPORTS

BIOMECHANICS AND SPORTS
9.1 Meaning and Importance of
Biomechanics in Physical Education and
Sports
9.2 Newton’s Law of Motion and its
Application in Sports
9.3 Levers and its types and its Application
in Sports
9.4 Equilibrium- Dynamic and Static and
Centre of Gravity and its Application in
Sports
9.5 Force- Centrifugal and Centripetal and
its Applications in Sports

9.1 Meaning of Biomechanics
 The study and analysis of human
movement patterns in sports is
called Biomechanics
 The study of the structure and
function of biological systems such
as humans, animals, plants,
organs, and cells by means of the
methods of mechanics
 The application of mechanical laws
to living structures

9.1 Importance of Biomechanics in Physical
Education and Sports
1. Helps in Improving Technique
a) Correct or rectify the errors of a sports
person to improve the execution of a skill
b) Discover a new and more effective
technique for performing a sport skill
c) Fosbury Flop and straddle technique
d) Qualitative biomechanical analysis for
correction
e) Quantitative biomechanical analysis for
discovering new techniques

9.1 Importance of Biomechanics in
Physical Education and Sports
2. Helps in Improving Equipment
a) Helps in improving the designs of the
equipment
b) Shoes & sports clothes design improved
c) Better equipment improves performance
and reduces the risk of injury
d) Better Rackets in racket games
e) Better Helmets to reduce risk of injury in
ice hockey, football and many other games
f) Aerodynamic clothing in skiing, speed
skating, cycling, swimming etc.

3. Helps in improving the performance
a) By utilizing biomechanics to improve
techniques
b) By utilizing biomechanics to improve
equipment
c) By utilizing biomechanics to reducing the
risk of sports related injuries

4. Helps in preventing injuries
a) Identifies the causes of injury
b) Helps in process of rehabilitation
c) By identifying cause and rehabilitation
exercises changes are made in techniques,
equipment to reduce the risk of sports
related injuries

5. Helps in the improvement of the
training
a) Mechanical analysis of the technical
deficiencies of a sports person helps
identify the type of training required
b) The weak areas may be strength,
endurance, speed of movement or body
actions
c) Customized training can be imparted
to the sports person

6. Helps in improving teaching and
learning process
a) Biomechanics helps in moving the body
with precision
b) Understanding of biomechanics helps the
teacher to take right decisions
c) Understanding of biomechanics helps
sports person to learn his weaker areas
and provides motivation to correct the
actions/ postures to enhance performance
and prevent injuries

9.2 Newton’s Laws of motion and
their application in Sports
 When exploring the area of
biomechanics and human movement, it
is useful to look at motion through the
observations made by Sir Isaac
Newton.
 Newton was a famous seventeenth-
century scientist who developed the
three laws that govern all motion.

9.2 Newton’s 1st Law – The law of
Inertia
 ‘A body continues in its state of rest or
uniform motion unless acted upon by an
unbalanced force.’
 In other words, a body will remain at
rest or in motion unless acted upon by a
force. In order to get a body moving, a
force must overcome the body’s
tendency to remain at rest or inertia.
The amount of inertia a body has
depends on its mass.

Newton’s 1st Law – The law of inertia
 This soccer ball will remain at rest, until a
force acts on it

9.2 Newton’s 2nd Law of Acceleration
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.

9.2 Newton’s 2nd Law of Acceleration
 When a force is applied to an object it
will move in the direction the force was
applied, and, depending on the size of
the force and the size of the object, the
object will accelerate accordingly.
 Smaller object will move faster than a larger one
 A greater force will move an object faster than
a smaller force.

Newton’s 2nd Law – mass, force & acceleration
f = ma

9.2 Newton’s 2nd Law of Reaction
 ‘Whenever a force is applied there is an
equal and opposite reaction.’
 If an athlete exerts a force onto the ground in
order to push off, the ground will exert an
equal and opposite force on the athlete,
pushing them up into the air.
 The first force of the athlete pushing into the
ground is called an action force. The second
force is called the reaction force (when the
second body applies an opposing force back).

Newton’s 3rd Law – action & reaction

Application of force summation – free-throw
shot technique

Force summation
 To give an object momentum in activities such as
throwing, kicking or striking an object, the amount of
momentum given to the object is determined by ‘the
sum of all forces generated by each body part’ (i.e.
Force summation).
 To gain maximum momentum, the force needs to be
generated by:
1. Using as many segments of the body as possible.
2. In the correct sequence, using large muscles first
and then the smallest muscles last but fastest.
3. With correct timing.
4. Through the greatest range of motion.

Application of force summation – free-throw
shot technique
 In order to maximise power and efficiency of the
shot, the whole body is used.
 Your body does not move all at once.
 The shot begins with the movement of the legs,
pushing into the ground.
 The force is then returned back up the legs, up
to the shoulders, down the forearms right to the
release of the ball at the fingertips.

9.3 Levers and
its Types and its
application in
Sports

© 2007 McGraw-Hill Higher
Education. All rights reserved
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Lever is a simple Machine
 Machines function in four ways
◦ balance multiple forces
◦ enhance force in an attempt to reduce
total force needed to overcome a
resistance
◦ enhance range of motion & speed of
movement so that resistance may be
moved further or faster than applied
force
◦ alter resulting direction of the applied
force

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Levers
 Levers rotate about an axis as a result
of force (effort, E) being applied to
cause its movement against a
resistance or weight
 In the body
bones represent the bars
joints are the axes
muscles contract to apply
force

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Levers
 Resistance can vary from maximal to
minimal
◦ May be only the bones or weight of body segment
 All lever systems have each of these three
components in one of three possible
arrangements

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Levers
 Three points determine type of
lever & for which kind of motion it
is best suited
◦ Axis (A)- fulcrum - the point of
rotation
◦ Point (F) of force application (usually
muscle insertion)
◦ Point (R) of resistance application
(center of gravity of lever) or
(location of an external resistance)

Types of Levers
 1st class lever – axis (A)
between force (F) & resistance
(R)
 2nd class lever – resistance (R)
between axis (A) & force (F)
 3rd class lever – force (F)
between axis (A) & resistance
(R)

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• AFR
Class 3
| Resistance Arm |
• ARF
Class 2
| Force Arm |
Types of Levers
• FAR
Class 1
A
F R
| Force Arm || Resistance Arm |
A
R
| Resistance Arm |
F
A
R
| Force Arm |
F

Class 1 Lever : FAR
Fulcrum
Effort
Load

Class 2 Lever : ARF
Load
Fulcrum
Effort

Class 3 Lever : AFR
Load
Fulcrum
Effort

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Types of machines found in the body
 Musculoskeletel system arrangement
provides for 3 types of machines in
producing movement
◦ Levers (most common)
◦ Wheel-axles
◦ Pulleys

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Types of Levers in Human Body
 Humans moves through a system of levers
 Levers cannot be changed, but they can be
utilized more efficiently
◦ lever - a rigid bar that turns about an axis of
rotation or a fulcrum
◦ axis - point of rotation about which lever moves
 In the human body, levers are made up of
the joints (fulcrum) and the bones that
connect them to the objects being moved.

Application of Levers in Sport
 Human leverage for sport skills requires
several levers
◦ throwing a ball involves levers at shoulder,
elbow, & wrist joints
 The longer the lever, the more effective it
is in imparting velocity
◦ A tennis player can hit a tennis ball harder with
a straight-arm drive than with a bent elbow
because the lever (including the racket) is
longer & moves at a faster speed

9.4 Equilibrium-
Dynamic and Static
and
Centre of Gravity
and
its Applications in
Sports

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9.4 Equilibrium
 Equilibrium - state of zero acceleration
where there is no change in the speed
or direction of the body
◦ Static
◦ Dynamic
 Balance - ability to control equilibrium,
either static or dynamic

9.4 Types of Equilibrium
 Static equilibrium - Body is at rest or
completely motionless
 Dynamic equilibrium - all applied & inertial
forces acting on the moving body are in
balance, resulting in movement with
unchanging speed or direction
 To control equilibrium & achieve balance,
stability needs to be maximized

9.4 Principles of Stability
 Stability is the resistance to a
◦ change in the body's acceleration
◦ disturbance of the body's equilibrium
 Stability is enhanced by determining body's
center of gravity & appropriately changing it
 Center of gravity - point at which all of
body's mass & weight are equally balanced
or equally distributed in all directions
 Balance - important in resting & moving
bodies

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 General factors applicable to enhancing
equilibrium, maximizing stability, &
ultimately achieving balance:
1. A person has balance when the
center of gravity falls within the base
of support
2. A person has balance in the direct
proportion to the size of the base.
The larger the base of support, the
more balance

3. A person has balance depending on
the weight (mass).The greater the
weight, the more balance
4. A person has balance, depending on
the height of the center of gravity
The lower the center of gravity, the
more balance
5. A person has balance, depending on
where the center of gravity is in
relation to the base of support
Balance is less if the center of gravity
is near the edge of the base

9.4 Centre of gravity
 Centre of gravity can be defined as “the
single point at which all parts of an object
are equally balanced”.
 A persons centre of gravity can change
depending on their body position as the
centre of gravity is the exact point
where all parts of an object are equally
balanced.

= Centre of gravity
For a ‘normal’ human being standing upright,
their centre of gravity lies around the area of
their navel

Centre of gravity of a boy whose hands
are stretched in the air
= Centre of gravity

The centre of gravity can also lie outside
an object, especially if the object is bent
over or leaning in a certain direction
9.4Centre of gravity
= Centre of gravity

Line of gravity
 Line of gravity is the vertical line that
passes through the centre of gravity to the
ground.
 If the line of gravity falls within the
object’s base of support (i.e. its contact
with the ground), the object is relatively
stable.
 If the line of gravity falls outside the
object’s base of support (i.e. its contact
with the ground), the object is relatively
unstable.

Line of gravity
Centre of
gravity
STABLE
Centre of
gravity
UNSTABLE
Line of gravity Line of gravity

Base of support – The object on the left is
more stable because of its relatively larger BOS
 BOS is the area within an objects point of contact with the
ground. The larger the area the base of support covers,
the more stable an object will be.
Wide BOS
Narrow BOS
BOS
BOS

9.5 Force-
Centripetal and
Centrifugal
and
its Applications in
Sports

9.5 Force
 Forces either push or pull on an object
in an attempt to affect motion or
shape
 Without forces acting on an object
there would be no motion
 Force - product of mass times
acceleration
 Mass - amount of matter in a body

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9.5 Force
Force = mass x acceleration
F = M x A
 Momentum (quantity of motion) - equal to
mass times velocity
 The greater the momentum, the greater the
resistance to change in the inertia or state of
motion

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9.5 Factors related to Movement
Activities
1. The production of Force
2. The application of Force
3. The absorption of Force

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Activities
 External forces are produced from
outside the body & originate from
gravity, inertia, or direct contact
 Only muscles can actively generate
internal force, but tension in tendons,
connective tissues, ligaments, and
joints capsules may generate passive
internal forces

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Activities
 The appropriate sequence to get
maximum force is necessary

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Activities
2. The application of Force
 The force on an object must be applied
in the direction in which it has to travel
 All activities require a summation of
forces from the beginning of movement
in the lower segment of the body to the
twisting of the trunk and movement at
the shoulder, elbow, and wrist joints

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Activities
 Significant mechanical loads are
generated & absorbed by the tissues of
the body
 Tension in tendons, connective tissues,
ligaments, and joints capsules may
generate passive internal forces

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Activities
 Internal forces can
◦fracture bones
◦dislocate joints
◦disrupt muscles & connective tissues
 To prevent injury or damage from
tissue deformation the body must
be used to absorb energy from
both internal & external forces

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9.5 Centripetal & Centrifugal Force
When an object is rotating around a
fixed axis in a circular path, two
opposing forces act on the object-
1. Centripetal Force
2. Centrifugal Force

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9.5 Centripetal Force
The force which keeps the body
moving with a uniform speed along
a circular path and is directed along
the radius towards the centre
1. Causes object to move
towards the centre

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9.5 Centrifugal Force
When centripetal force acts upon a
body, another force equal to the
centripetal force but opposite to the
direction also acts upon it. This
force is called Centrifugal force.
1. Causes object to move away
from the centre

9.5 Force – its Application in Sports
 In the performance of various
sport skills such as throwing,
many applications of the laws of
leverage, motion, and balance may
be found
 In throwing, the angular motion of
the levers (bones) of the body
(trunk, shoulder, elbow, and
wrist) is used to give linear
motion to the ball when it is
released

Application
of
centripetal
and
Centrifugal
force
in
Sports

Chapter 9 Biomechanics and Sports

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