Transcript Biomechanics - study

This achievement standard requires
demonstration of understanding of
functional anatomy and
biomechanical principles and how
they relate to physical activity,
through participation and/or
observation
Learning Intention
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To understand what Biomechanics is and
how it can be applied to Badminton.
To develop an understanding of the key
aspects of Biomechanics as part of the
learning process.
Defining Biomechanics
Bio = body Mechanics = forces and motion
“Biomechanics is the science
concerned with how forces (internal
& external) act on the human body
and the effects these forces have on
the motion of the body”.
WHAT IS BIOMECHANICS?
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It involves the study of Forces and
Motion involved in human movement,
particularly sport performance.
In other words, biomechanics looks at
what is the best technique for generating
forces and producing the most efficient
motion, in order to maximise sport
performance (technique).
QUESTION????
 What
is the best way to kick
a rugby ball?, hit a golf
ball?, throw a softball?,
shoot a basketball?, hit a
tennis ball?
FORCES
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Force = “is a push
or pull that
changes a body's
state of rest or
motion”.
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Internal Forces –
generated within
the body e.g..
forces due to
muscle contraction
External Forces –
acting outside from
the body e.g..
gravity
FORCES
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In sport athletes primarily produce force within the body
by contracting the muscles.
Types of Forces
Muscular
Gravitational
Frictional
Aerodynamic
Contact (ground or another body),
Inertial
Elastic
Centripetal
Centrifugal
TYPES OF FORCES
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Muscular Force = due to the
contraction of muscle.
Friction Force = due to two surfaces in
contact with each other and the tendency
of the two surfaces to oppose each others
motion e.g.. mountain bike vs. racing bike
tyres, sports shoe soles for various sports,
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Gravity = is the downward acting force
which attracts bodies to the centre of the
earth.
Aerodynamic Force = (is a type of
frictional force) due to air resistance,
where particles of air resist the motion of
a body through it. e.g.. use of aero bars
for cycling, spin in a tennis serve, swing in
bowling a cricket ball
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Contact = the force involved in a collision
of bodies or the ground. e.g.. Scrum or
Tackling collisions in rugby, hitting or
catching a cricket ball, running
Inertia = the force of an object due to
its mass (whether moving or stationary)
e.g.. catching a medicine ball vs. catching
a volleyball, catching a cricket vs. tennis
ball
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Centripetal = force
which is directed in
toward the central
axis of a rotating
body.
Centrifugal = force
directed outward
away from the central
axis of a rotating
body.
Task
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For each of the following, identify the forces
acting and what or who they are acting on.
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Kicking a soccer ball
Tennis serve
Throwing a javelin
A rugby tackle
Hitting a ball in cricket
Catching a medicine ball
Somersault in gymnastics
Newton's 3 Laws
You Tube - Three Laws of Motion
Newton’s First Law
The Law of Inertia
(The 1st Law of Motion)
Newton's First Law of Motion The Law of Inertia
A body will remain in a state of rest or in
uniform straight line motion, unless acted
upon by a force to change that state of
rest or motion”.
e.g.. Daniel Carter kicking a penalty; the ball will
remain at rest until Dan applies a force with his
foot. The ball would travel in a straight line into
the sky, but is acted upon by gravity and air
resistance (wind) to change its motion
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Newton's First Law of Motion The Law of Inertia
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Moving Inertia
An object in motion tends to remain in
motion and to travel in a straight line with
uniform velocity unless acted upon by
some external force.
Stationary Inertia
An object at rest tends to remain at rest
unless acted upon by some external force.
Newton's First Law of Motion The Law of Inertia
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Inertia
In order to set in motion a body presently at
rest, you need to overcome the tendency of the
body to remain at rest. This tendency of the
body to remain at rest is called it's stationary
inertia. The applied force must overcome the
body's stationary inertia for motion to occur. If
the force is not great enough to overcome the
body's stationary inertia the body will remain at
rest.
Inertia
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A very heavy Barbell has stationary inertia,
A large force overcomes this and action
occurs. The heavier barbell has greater
stationary inertia, force cannot overcome
this, motion does not occur and barbell
remains at rest.
Inertia
An object in motion tends to remain in
motion and this tendency is called the
body's moving inertia.
A force must overcome the body's moving
inertia in order to alter the body's motion.
The motion of the basketball is altered, i.e.
the ball is deflected when a force is
applied by the hand.
NEWTONS 3 LAWS OF MOTION
The Law of
Acceleration
(The 2nd Law of
Motion)
Newton's Second Law of Motion =
The Law of Acceleration
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The acceleration (change in motion) of a
body is proportional to the force causing
it, and the change takes place in the
direction that the force acts.
Newton's Second Law of Motion, the law
of acceleration can be expressed as:
Acceleration = force / mass
Newton's Second Law of Motion =
The Law of Acceleration
When a body is acted upon by a force......
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The greater the force, the greater the
acceleration.
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The smaller the mass, the greater the
acceleration.
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The change in motion takes place in
the direction in which the force is
applied.
NEWTONS 3 LAWS OF MOTION
The Law of ActionReaction
(The 3rd Law of Motion)
Newton's Third Law of Motion
Law of Action Reaction
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Newton's Third Law of Motion states that “
“For every action, there is an equal and
opposite reaction.”
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Newton's Third Law of Motion
Law of Action Reaction
For every action there is an equal and
opposite reaction;
A force acting anywhere always has a
force equal to that acting in the opposite
direction
Forces work in pairs opposing one another
The initial force (action force) is opposed
by a second force (reaction force)
Force Summation
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Force generation by the body is explained
in terms of force summation the
sequential acceleration of body segments,
timing of body parts, Range of Motion
(impulse) and Stretching Out.
The acceleration of body parts can be
greatly improved through the process of
FORCE SUMMATION.
Force = mass x acceleration
Force Summation
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In many sporting actions such as kicking a rugby
ball, the desired movement is a combination of a
number of body parts and the forces each body
part generates.
These forces are added together through a
sequence of body movements to generate a far
greater force.
The correct sequence and timing of body parts
permits the athlete to produce a greater force
and therefore attain optimal velocity at release
or contact.
Generating greater force
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The body parts that are large muscle
groups can generate large forces. The
large force causes a large acceleration in
that body part. When that body part
reaches peak force then the body part has
reached peak acceleration, after which the
body part would start decelerating (slow
down).
Peak force diagram (see teacher notes)
Force Summation & Timing
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The sequence and timing of the body
movements are extremely important in order to
obtain maximum force generated by each
successive body part and therefore maximise the
efficiency of the movement.
Each successive body part should begin to
accelerate when the previous limb has reached
peak force, and therefore peak acceleration
Look at these examples;
Girl throw Man throw
The fewer body parts used = less force
Force summation: ROM and
stretching out
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Impulse: Applying a Force for a longer period of
time
Muscular force has to be produced when athletes want
to get moving or they want to accelerate an object such
as a soccer ball and give it momentum. The force that
athletes apply always takes time. When athletes apply
force to an object over a certain time , we say that the
athlete has applied an IMPULSE to the object.
IMPULSE = FORCE x TIME (force is applied for)
The longer the time the force is applied for, the greater
the impulse.
Athletes can apply an impulse to their own bodies or to
another athlete or to an object.
Example of ROM
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Javelin
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The combination of force and time depends on the needs of the
skill and sport. Some skills, such as punches in boxing, require
tremendous forces applied over a very short time frame. Other
skills like throwing a javelin require forces applied over a longer
timeframe. An expert javelin thrower accelerates the javelin by
pulling it from way behind his body and releasing it far out in
front. Long arms are beneficial as is a backward lean entering
the throw position, why? The athlete applies the force for a long
period and therefore more overall force is produced.
To do this an athlete will increase the range of motion, which
allows them to apply the force for a longer period of time.
Javelin throw
Some working examples
Use these clips to apply the principles of
force summation we have just discussed
Carter kick
Tennis serve
Tennis Serve 2
Hammer throw
Caber toss
Motion
Forces produce three types of motion:
 Deformative Motion: changing the shape
of the body
 Linear Motion : moving a body from one
place to another in a straight line.
 Angular Motion: or rotation , this is
where the body rotates or spins about an
axis (either internal axis or external axis)
Linear Motion
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Where movement
occurs in a straight
line. During
translation, all parts
of a body move
through the same
distance in the same
direction in the same
time.
Angular Motion
During angular
motion or rotation all
parts of a body move
in a circular path
around a central axis
moving through the
same angle, in the
same direction in the
same time.
Angular Motion
There are two types of axis
of rotation:
 Internal Axis this is when
the axis passes through
the body, usually at a
joint, e.g.. the lower leg
rotating a bending at
knee joint occurs.
 External Axis this is when
the axis is outside the
body, e.g.. a giant swing
in gymnastics.
General Motion
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In physical activity the motion
that occurs is quite often a
combination of linear motion
and rotation.
General motion can be
described as linear movement
of the whole body that is
achieved due to the angular
motion of some of the body
parts.
Projectile Motion
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Projectile:
Any body that is
released into the air
becomes projectile
and the motion of the
projectile is governed
by a number of
factors
Forces influencing projectile motion
Propelling Force
Gravity
Air Resistance
Propelling force
(force at impact or release)
The most important force affects the
projectile in how far and/or how high it
travels.
Gravity
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Acts equally on all objects, accelerating
the object towards the ground.
Gravity acts on the vertical component of
the objects motion
Air resistance
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Air particles through which the object travels,
opposes its forward motion.
Air resistance opposes the horizontal component
of the projectiles motion.
The lighter the object or the larger its surface
area, the more it is affected by air resistance.
Air resistance also increases with speed. e.g. a
golf ball drive is more affected than a chip shot
onto the green.
Air Resistance
Quantifying Motion
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Having identified the types of motion a body can have;
biomechanists need to then quantify (measure) the
motion (i.e. describe motion in terms of certain
quantities) in order to calculate the forces acting. This
information can be used to compare and analyse the
efficiency of the motion and movements of the athlete.
When we talk about the motion of a body or object we
say it moves through a certain displacement (or
distance) in a certain time interval. (i.e. it has a certain
velocity). If that velocity is changing then the is
undergoing acceleration or deceleration
Measuring your motion
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See handout and do practical
Factors influencing the Flight Path
or Trajectory of a projectile
Velocity of release
Angle of release
Height of release
Spin
Velocity of release
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The speed at which the projectile leaves
the propelling force (bat if hitting, hand if
throwing, ground if jumping)
Height of release
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Relative to the height at which the
projectile lands, whether it is above or
below the height at which the projectile
was released.
Angle of release
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The angle that the projectile is released on
its flight path.
Spin
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Imparting spin on the projectile (e.g.. top
spin or back spin in tennis or hooking or
slicing as in golf), will alter the projectiles
flight path, toward the direction of the
spin.
This is called the “magnus effect”.
Centre of Gravity, Balance and Stability
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Centre of gravity in physical activity is explained as it
relates to balance and stability.
Balance implies co-ordination and control, so that the
athlete can neutralise those forces that would otherwise
disrupt their performance. External forces such as
gravity, friction and contact forces applied by opponents
can all unbalance there position and upset their
performance.
Stability relates to how much resistance an athlete
“puts up” against having their balance disturbed. The
more stable an athlete, the more resistance the athlete
puts up against disruptive forces.
Centre of Gravity
The point where an
object mass is
considered to be
concentrated
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Generally your centre of
gravity may be found
using the following
calculation:
MALES: 57% of height
(height x 0.57)
FEMALES: 55% of height
(height x 0.55)
Principles of Equilibrium
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The equilibrium of a body is said to be STABLE
if, when being slightly displaced the body tends
to return to its original position.
The equilibrium is UNSTABLE if the body tends
to move further from the original position.
Equilibrium relies on:
1. The location of the centre of gravity in
relation to the base of support
2. The direction of the forces acting
Principles of Equilibrium
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Principle 1
An Athlete increases their stability
when their Line of Gravity is centralised within their base
of support.
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Principle 2
An athlete increases their stability
when they increase size of their Base of Support.
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Principle 3
An athlete increases their stability
when the lower the height of their Centre of Gravity
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Principle 4
An athlete increases their stability
when they extend their base ,Line of Gravity in the
direction of an oncoming force.
Principles of Equilibrium
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Principle 5
An athlete increase stability by
increasing mass.
Principle 6
An increase in Friction can improve an
athlete’s Stability
Principle 7
Stability
Rotation can improve an athlete’s
Principle 8
Shifting the line of gravity toward
oncoming forces can improve stability
Principles of Equilibrium
Stability of a body depends on :
The height of the centre of gravity
The centrality of the line of gravity
The size of the base of support
The direction of applied forces
The mass of the body
Friction
Rotation
Momentum
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To understand the concept of momentum, how it
influences motion and the principle of TRANSFER of
MOMENTUM.
Momentum is the product of a MASS that has VELOCITY
It is the amount of motion a moving object has,
is calculated by multiplying the mass of the object by its
velocity
Momentum = MASS x VELOCITY
Transfer of Momentum Within a Body
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Momentum can also
be redistributed from
one part of the body
to another part of
your body.
This transfer of
momentum is
common in jumping,
diving and
gymnastics.
Transfer of Momentum
from one Body to Another Body
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Momentum can also be transferred from one
body to another.
The momentum that an object possesses due to
its motion is an important consideration when
there is a collision of objects. In such collisions
MOMENTUM is TRANSFERRED from one
body to another and vice versus (Newton's 3rd
Law of Motion).
Phases of Execution
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A phase is a connected group of
movements that appear to stand on their
own and that the athlete joins together in
the performance of the total skill
preparation phase = the initial stance and
preparatory movements
 action phase, = the force producing movements
 post action phase = the follow through or
recovery
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Phases of Execution
for a Javelin Throw
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Preparation phase
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Grip and Carry
Run Up
Shoulders rotated back
Javelin Drawn Back
Cross-over stepping
into final throwing
stance
Phases of Execution
for a Javelin Throw
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Execution /action phase = (force producing
movements)
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Athlete takes are large step into the throwing stance
Body Tilted backwards
Centre of Gravity Lowered by flexed rear leg
Rear Leg rotates forward in direction of throw
Hips rotate forward in direction of throw
Torso rotates and pulls shoulder and arm forward
Lead arm swings back pulling chest and throwing arm
forward
Elbow flexes then extends as it comes forward to release
Phases of Execution
for a Javelin Throw
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Post action phase =
Follow Through
 Trailing leg steps forward
 Shoulder and Torso rotate on Follow through
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Newton's 3 Laws of Motion and
Movement Sequence
Newton's 1st Law
 The javelin, soccer ball, rugby ball will
remain at rest until acted on by a force
applied by the player.
 The Baseball will remain in straight line
motion until acted on by a force Bat and
Gravity , which act to change its motion
Newton's 3 Laws of Motion and
Movement Sequence
Newton's 2nd Law
 The acceleration of the javelin, soccer ball,
rugby ball or baseball is proportional to the force
applied by the athlete (and bat)
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The acceleration of the javelin, soccer ball,
rugby ball or baseball occur in the direction that
the athlete or bat apply the force
Newton's 3 Laws of Motion and
Movement Sequence
Newton's 3rd Law of Motion
 The bat applies an action force to the ball,
but the ball also applies a equal and
opposite reaction force back on the bat
 The players foot applies an action force to
the soccer or rugby ball, but the ball also
applies a equal and opposite reaction
force back on the players foot
Force Summation
and Movement Sequence
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To generate the most force the athlete will use a number
of body segments to generate force
The force generated in each body segment will be
added together as each body part accelerates in a
sequential order.
The following example describes the sequential
acceleration of body parts, resulting in successive force
summation:
Throwing/Hitting =
Legs→hips→torso→shoulder→arm or
Kicking = Shoulder→Torso→Hips→ Leg
Force Summation
and Movement Sequence
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In order to generate the greatest force most effectively,
in any throwing, hitting or kicking activity.
The timing of when each successive body part moves is
important.
Each body segment should accelerate or begin to
generate force once the previous segment has reached
its peak force stage.
The following body part (e.g.. forearm) should begin to
accelerate once the preceding body part (e.g.. upper
arm) has reached peak acceleration, which would have
accelerated once the previous body part (trunk) had
reached its peak acceleration.
Force Summation
and Movement Sequence
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If the body parts move to early, before the previous limb
reaches peak force or too late, after the previous limb
has reached peak force. Then less force is produced.
By increasing the Range of Motion the athlete can apply
the force for a longer period of time (impulse = force x
time) resulting in a larger force being applied increasing
the range of motion allows for increase in force.
In turn by increasing the range of motion muscles are
Stretched Out and the muscles can then contract more
forcefully
Projectile Motion
and Movement Sequence
Forces influencing projectile motion
Propelling force
The most important force affect the projectile in how far
and/or how high it travels.
Gravity
Acts equally on all objects, accelerating the object towards
the ground. Gravity acts on the vertical component of
the objects motion.
Air resistance
Air particles through which the object travels, opposes its
forward motion. Air resistance opposes the horizontal
component of the projectiles motion
Factors influencing the Flight Path or
Trajectory of a projectile.
Velocity of release
The speed at which the projectile leaves the propelling
force (bat if hitting, hand if throwing, ground if jumping)
Angle of release
The angle that the projectile is released on its flight path.
Height of release
Relative to the height at which the projectile lands, whether
it is above or below the height at which the projectile was
released.
Spin
Imparting spin on the projectile (e.g.. top spin or back spin in tennis or
hooking or slicing as in golf), will alter the projectiles flight path, toward
the direction of the spin. This is called the “magnus effect”.
Centre of Gravity
Balance and Equilibrium
Stability in a headstand and handstand
can be improved by:
Increasing the size of the base of support.
Maintaining the centrality of the line of gravity inside
the base of support.
Lowering the height of the centre of gravity.
The direction of applied forces.
The mass of the body.
Friction.
Rotation.
Biomechanics Summary
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Forces and Motion involved in human movement (sport
performance)
Force - push, pull that change state of rest or motion of a body,
 F = m x a
Types of forces, effects of forces, impulse (range of motion)
Newton's Three Laws of Motion
Law of Inertia, Law Acceleration and Action/Reaction.
Force Summation
sequential acceleration of body segments, timing of body parts and
range of motion and stretching out.
Biomechanics Summary
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Motion
Linear, Angular and General motion, Measuring Motion – equations.
Projectile Motion
Forces acting = propelling force, gravity, air-resistance,
Influencing factors.= speed, height and angle of release, spin,
gravity, air resistance.
Centre of Gravity, Balance, Stability and Equilibrium
Base of Support, Line of Gravity centralised, Height of C of G,
Extend base & C of G into oncoming forces, increase Mass, Increase
Friction and rotation.
Biomechanics Summary
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Momentum and Transfer of Momentum
Amount of motion a moving object has,
Force = mass x velocity
In a collision, the momentum of one body can be
transferred to another.
A complex movement sequence is described in
terms of the phases of execution.
Javelin, Baseball Hit, Place Kicking a Ball (Soccer or Rugby),
Phases of execution - preparation phase,
execution/action (force producing) phase, post action
phase.
Biomechanics Summary
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Biomechanical principles are described as they
apply to the sequence.
Javelin, Baseball Hit, Place Kicking a Ball (Soccer or Rugby).
Biomechanical principles-, Newton’s laws, momentum,
projectile motion, force summation, timing of body parts.
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Biomechanical principles are described as they
apply to the sequence.
Gymnastic Balance (Headstand-Handstand)
Biomechanical principles – stability and equilibrium,
centre of gravity, base of support, Line of Gravity
centralised