Sport Biomechanics Understanding how a skill is performed mechanically is an important stepping stone to understanding how it can be learned.

Sport Sport BiomechanicBiomechanic

ssUnderstanding how a skill is performed Understanding how a skill is performed mechanically is an important stepping mechanically is an important stepping stone to understanding how it can be stone to understanding how it can be

learned. learned.

Basic Laws of BiomechanicsBasic Laws of Biomechanics

Sir Isaac NewtonSir Isaac Newton developed three laws to developed three laws to explain the relationship between explain the relationship between forcesforces acting on a body and the acting on a body and the motionmotion of the of the body. body.

What is a Force?What is a Force?

A force is a push or a pull. Forces are A force is a push or a pull. Forces are measured in Newtons. Did you know that measured in Newtons. Did you know that forces only exist when objects interact!forces only exist when objects interact!

What is a Force?What is a Force?

A force gives energy to an object. A force gives energy to an object. Whenever two objects touch, forces are Whenever two objects touch, forces are involved. involved.

What is a Force?What is a Force?

A force can cause acceleration, a change A force can cause acceleration, a change in direction or deceleration. A force is in direction or deceleration. A force is NOTNOT required to keep an object in motionrequired to keep an object in motion

Examples:Examples:

-Drag, Friction, Thrust, Gravity, Weight, -Drag, Friction, Thrust, Gravity, Weight, MagnestismMagnestism

Law 1: Law of InertiaLaw 1: Law of Inertia

An object at rest will remand at rest unless An object at rest will remand at rest unless acted upon by some external force. acted upon by some external force.

The greater the The greater the inertiainertia an object has the an object has the greater the force needed to move it.greater the force needed to move it.

Objects at rest remain at rest unless acted on by Objects at rest remain at rest unless acted on by a net force.a net force.

A lot of inertia! A lot of inertia! Very little inertia. Very little inertia.

Since the train is so huge, it is Since the train is so huge, it is difficult to change its speed. In difficult to change its speed. In

fact, a large net force is required to fact, a large net force is required to change its speed.change its speed.

Since the baby carriage is so small, it Since the baby carriage is so small, it is very easy to change its speed. A is very easy to change its speed. A

small net force is required to change small net force is required to change

its speedits speed..

Objects in motion remain in motion in a straight Objects in motion remain in motion in a straight line (unless acted upon by an outside force).line (unless acted upon by an outside force).

A lot of inertia! A lot of inertia! Very little inertia. Very little inertia.

Since the train is so huge, it is Since the train is so huge, it is difficult to stop it once it is moving. difficult to stop it once it is moving. It is difficult to change its speed. In It is difficult to change its speed. In fact, a large net force is required to fact, a large net force is required to

change its speed.change its speed.

Since the soccer ball is so small, it is Since the soccer ball is so small, it is very easy to stop it once it is moving. very easy to stop it once it is moving. A small force is required to change its A small force is required to change its

speed.speed.

Law 1: Law of InertiaLaw 1: Law of Inertia In what sports would a lot of inertia be to the In what sports would a lot of inertia be to the

athletes advantage?athletes advantage?

--Sumo, Scrumming Sumo, Scrumming

In what sports would a lot of inertia be to the In what sports would a lot of inertia be to the athletes disadvantage?athletes disadvantage?

- Sports requiring quick Sports requiring quick - change of directionchange of direction

Inertia & the Golf SwingInertia & the Golf Swing

How does inertia affect the golf swing?How does inertia affect the golf swing?

Golf BallClub Head

Law 2: Law of AccelerationLaw 2: Law of Acceleration

When a When a forceforce acts upon a acts upon a massmass, the result is , the result is accelerationacceleration of that mass. of that mass.

a.a. The greater the The greater the forceforce, the great the , the great the acceleration.acceleration.

b.b. The smaller the The smaller the massmass, the greater the , the greater the accelerationacceleration..

c.c. The mass will The mass will accelerateaccelerate in the in the direction the forcedirection the force is is applied. applied.

F = m x a

(force) (mass) (acceleration)

Big masses are hard Big masses are hard to accelerate. Big to accelerate. Big

masses require big masses require big forces to change forces to change

speed. speed.

Small masses are Small masses are easy to accelerate. easy to accelerate.

Small masses require Small masses require small forces to change small forces to change

speed speed

Assume that both steam engines below Assume that both steam engines below apply the same amount of force.apply the same amount of force.

A heavy train has a difficult A heavy train has a difficult time accelerating. Big time accelerating. Big masses require big forces to masses require big forces to

change speedchange speed. .

When the same force is When the same force is applied to a less massive applied to a less massive train its acceleration is train its acceleration is greater. Small masses greater. Small masses require small forces to require small forces to change speed. change speed.

Law 2: Law of AccelerationLaw 2: Law of Acceleration

How can we apply this law of acceleration to the How can we apply this law of acceleration to the golf swing?golf swing?

- The greater the initial force (contracting - The greater the initial force (contracting muscles), the greater the acceleration of the club muscles), the greater the acceleration of the club head and the greater acceleration on the golf head and the greater acceleration on the golf ball on contact. ball on contact.

- The - The greatergreater the force, the the force, the furtherfurther the golf ball the golf ball will travel. will travel.

Law 3: Action - Reaction LawLaw 3: Action - Reaction Law

For every action, there is an For every action, there is an equalequal and and oppositeopposite reaction. reaction.

When we apply a force this is known as an When we apply a force this is known as an action forceaction force..

The object we apply the force to, applies a The object we apply the force to, applies a force back, this is a force back, this is a reaction forcereaction force..

Law 3: Action - Reaction LawLaw 3: Action - Reaction Law

These two forces always These two forces always work in pairswork in pairs, , and are and are opposite in directionopposite in direction and and equal equal in size. in size.

The forces here are equal and opposite. Neither the dog nor its owner pulls with greater force.

They pull with the same force in opposite directions

The forces will be equal when the truck crashes into the car.

Since the car is smaller, the car will have a greater acceleration.

If forces are always equal and opposite, how If forces are always equal and opposite, how can anything move?can anything move?

Here is a famous problem: A horse is pulling on a cart, and the cart pulls back with the same amount of force. If all forces are equal, how can the horse and cart move?

Answer: The horse moves because the force he exerts with his hooves is greater than the force of the wagon pulling him back.

If forces are always equal and opposite, If forces are always equal and opposite, how can anything move?how can anything move?

What forces act on the cart? The horse pulls it forward, What forces act on the cart? The horse pulls it forward, and there is a backward force from the ground: friction. If and there is a backward force from the ground: friction. If the horses' pull exceeds the friction of the cart, it will the horses' pull exceeds the friction of the cart, it will accelerate. accelerate.

Acceleration will occur if one force pair (push of ground/push of horse)

is greater than another force pair (friction/pull of cart).

If forces are always equal and opposite, If forces are always equal and opposite, how can anything move?how can anything move?

Example 2: If the person's friction forces against the Example 2: If the person's friction forces against the floor are greater than the refrigerator's friction floor are greater than the refrigerator's friction forces, the fridge will accelerate.forces, the fridge will accelerate.

MotionMotion

Types

of

Motion

General Motion

Curvilinear Motion

Angular Motion

Linear Motion

Linear MotionLinear Motion

When all parts of the body move in a When all parts of the body move in a straight parallel lines (same distance straight parallel lines (same distance in same time). in same time).

ExamplesExamples

-Dropping a ball-Dropping a ball

-Sliding in to first base-Sliding in to first base

-Tobogganing down a hill-Tobogganing down a hill

Curvilinear motionCurvilinear motionWhen all parts of the body move in a When all parts of the body move in a curved path along parallel lines.curved path along parallel lines.

ExamplesExamples

-free fall sky diving-free fall sky diving-path of a tennis serve-path of a tennis serve-flight of golf ball-flight of golf ball

Angular MotionAngular MotionRotation about an axis that can be Rotation about an axis that can be either internal or external.either internal or external.

ExamplesExamples

-swinging around a high bar-swinging around a high bar-a bicep curl-a bicep curl-a golf swing-a golf swing

General MotionGeneral Motion

Linear motion of the body as a result Linear motion of the body as a result of angular motion of other parts of of angular motion of other parts of the body. the body.

ExamplesExamples- CyclingCycling- SwimmingSwimming- KayakingKayaking

Projectile MotionProjectile MotionAny object released into the Any object released into the

air is termed a projectile.air is termed a projectile.

All projectiles have a flight path and All projectiles have a flight path and flight time depending on how they flight time depending on how they affected by the variables below.affected by the variables below.

-Gravity

-Air Resistance

-Angle of Release

-Speed of Release

-Height of Release

-Spin

GravityGravityGravity acts on a body to give it Gravity acts on a body to give it massmass. .

The greater the The greater the massmass of an object the of an object the greater the influence of gravity upon it. greater the influence of gravity upon it.

What is the effect of gravity on a projectile?What is the effect of gravity on a projectile?

- - It decreases the height a projectile can It decreases the height a projectile can attain.attain.

GravityGravity

GravityGravity

Air ResistanceAir ResistanceAir resistance acts on the horizontal Air resistance acts on the horizontal component of a projectiles path. component of a projectiles path.

Angle of ReleaseAngle of ReleaseThe angle of release of a projectile The angle of release of a projectile determines the flight path.determines the flight path.

a.a. If the angle of release is high, the If the angle of release is high, the projectile has a longer flight time but projectile has a longer flight time but decreased distancedecreased distance. .

a.a. If the angle of release is low, the projectile If the angle of release is low, the projectile has less flight time but has less flight time but increased increased distancedistance**

**However if the angle is too low, distance is poor. However if the angle is too low, distance is poor.

Angle of ReleaseAngle of ReleaseHow is distance How is distance and height and height manipulated in manipulated in golf for the best golf for the best shot?shot?

- Angle of club head.- Angle of club head.

Speed of ReleaseSpeed of Release

Velocity (speed of motion) of release Velocity (speed of motion) of release will determine the size of the flight will determine the size of the flight path. path.

Height of ReleaseHeight of ReleaseThe greater the The greater the heightheight of release of release the greater the the greater the distancedistance gained gained

SpinSpinThere are There are two maintwo main types of spin types of spin

1. 1. Top spin-Top spin- distance is decreased distance is decreased with topspin. with topspin.

2. 2. Back spin-Back spin- distance is increased distance is increased with backspin.with backspin.

Back SpinBack SpinA backspin shot creates a region of low pressure A backspin shot creates a region of low pressure on top of the ball and a region of high pressure on top of the ball and a region of high pressure below. As a consequence, the ball floats suddenly below. As a consequence, the ball floats suddenly

thereby increasing the distance attainedthereby increasing the distance attained. .

TopspinTopspinQ. So how does Topspin work?Q. So how does Topspin work?

A. A topspin shot creates a region of A. A topspin shot creates a region of high pressure on top of the ball and a high pressure on top of the ball and a region of low pressure below. As a region of low pressure below. As a consequence, the ball dips suddenly consequence, the ball dips suddenly thereby decreasing the distance thereby decreasing the distance attainedattained

A golf ball acquires spin when it is hit. Backspin is imparted for almost every shot due to the golf club's loft (i.e., angle between the clubface and a vertical plane). A spinning ball deforms the flow of air around it similar to an airplane wing; a back-spinning ball therefore experiences an upward force which makes it fly higher and longer than a ball without spin.

The amount of backspin also influences the behavior of a ball when it impacts the ground. A ball with little backspin will usually roll out for a few yards/meters while a ball with more backspin may not roll at all, even backwards. Sidespin occurs when the clubface is not aligned perpendicularly to the plane of swing. Sidespin makes the ball curve left or right: a curve to the left is a draw, and to the right a fade (for right-handed players).

Accomplished golfers purposely use sidespin to steer their ball around obstacles or towards the safe side of fairways and greens. But because it's sometimes difficult to control or predict the amount of sidespin, balls may take an undesirable trajectory, such as hook to the left, or slice to the right (for right-handed players).

StabilityStability & &

BalanceBalance

Centre of GravityCentre of GravityThe point in the body about which all The point in the body about which all parts of the body are in balance or parts of the body are in balance or the point at which gravity is centredthe point at which gravity is centred

COG is not confined to one location, COG is not confined to one location, as the body moves so the COG as the body moves so the COG moves with it in the direction the moves with it in the direction the movement occursmovement occurs

•This runner has an upright trunk •Level pelvis •Centre of gravity is well behind the contact point of the leading foot •This allow progressive loading of the leading leg

RUNNING EXAMPLERUNNING EXAMPLE

•With a trunk leaning forwards •The centre of gravity is almost directly over the foot as it lands •The loading on the foot, ankle, knee, pelvis rises steeply

Increasing StabilityIncreasing Stability

Stability is increased when Centre of Stability is increased when Centre of Gravity is loweredGravity is lowered

Increasing StabilityIncreasing StabilityStability is increased when the line of Stability is increased when the line of gravity falls within the BOS (Base of gravity falls within the BOS (Base of SupportSupport

Increasing StabilityIncreasing StabilityStability is increased with increased massStability is increased with increased mass

Why?Why?

Greater inertiaGreater inertia – requires more force by – requires more force by an opponent to move the line of gravityan opponent to move the line of gravity

Eg. Rugby – a bigger forward pack has an Eg. Rugby – a bigger forward pack has an advantage in scrumsadvantage in scrums

Increasing StabilityIncreasing StabilityStability also is increased when BOS Stability also is increased when BOS is extended in the direction of an is extended in the direction of an oncoming forceoncoming force

Stability is increased when the line of Stability is increased when the line of gravity is moved towards an gravity is moved towards an oncoming forceoncoming force

Biomechanics Biomechanics of of

TorqueTorque(Rotational Force)(Rotational Force)

Biomechanics of TorqueBiomechanics of TorqueRotational movements play an Rotational movements play an important part in all sports skillsimportant part in all sports skills

Rotation can involve:Rotation can involve:

--the whole bodythe whole body (diving, gymnastics) (diving, gymnastics) --objectsobjects (pitching or bowling a ball) (pitching or bowling a ball)

--the body and equipment as leversthe body and equipment as levers (batting, golf)(batting, golf)

Axis of RotationAxis of RotationThe axes of rotation of the body act The axes of rotation of the body act through the COGthrough the COG

There are There are 3 axes3 axes of rotation of rotation

Longitudinal – eg pirouetteLongitudinal – eg pirouetteTransverse - eg forward rollTransverse - eg forward rollSagittal - eg cartwheelSagittal - eg cartwheel

LeversLeversLevers are designed to allow either a Levers are designed to allow either a greater resistance to be moved with greater resistance to be moved with a given force a given force

Or to increase the velocity (speed) at Or to increase the velocity (speed) at which an object can be moved using which an object can be moved using a given forcea given force

Parts of a LeverParts of a LeverLevers consist of 3 parts; Levers consist of 3 parts;

a)a) ResistanceResistanceb)b) ForceForcec)c) FulcrumFulcrum

The distance from where a force is applied to the The distance from where a force is applied to the fulcrum is called the fulcrum is called the force arm force arm (FA)(FA)

The distance from where a resistance acts to the The distance from where a resistance acts to the fulcrum is called the fulcrum is called the resistance arm resistance arm (RA)(RA)

First Class LeverFirst Class Lever

The fulcrum lies between the resistance and the forceThe fulcrum lies between the resistance and the force

FA shorter than RA favours speed and range of movementFA shorter than RA favours speed and range of movement

FA longer than RA favours force outputFA longer than RA favours force output

First Class LeversFirst Class Levers

Second Class LeverSecond Class Lever

The resistance lies between the pivot and the forceThe resistance lies between the pivot and the force

The force arm and the resistance arm are on the same side The force arm and the resistance arm are on the same side of the leverof the lever

The FA is always longer than the RAThe FA is always longer than the RA

Second Class LeversSecond Class Levers

Third Class LeverThird Class Lever

The force lies between the resistance and the fulcrumThe force lies between the resistance and the fulcrum

The FA is shorter than the RAThe FA is shorter than the RA

In third class levers, the force applied is always greater than In third class levers, the force applied is always greater than the resistancethe resistance

Third Class LeversThird Class Levers

TorqueTorqueAs all levers produce rotation about an axis, they As all levers produce rotation about an axis, they also produce also produce torque.torque.

Torque is defined as a Torque is defined as a turning forceturning force

T = F x DT = F x DTorque = Force x DistanceTorque = Force x Distance

The The greater the forcegreater the force applied to a given force applied to a given force arm the greater the torquearm the greater the torque

The The longer the forcelonger the force arm with a given force arm with a given force applied the greater the torqueapplied the greater the torque

Initiating RotationInitiating RotationIn order to initiate rotation on any In order to initiate rotation on any object, or human body an eccentric object, or human body an eccentric force must be appliedforce must be applied

An eccentric force is a force applied An eccentric force is a force applied away from the COGaway from the COG

Apply this principle to explain how a Apply this principle to explain how a pitching wedge works!pitching wedge works!

Angular Velocity and Angular Velocity and Speed of RotationSpeed of Rotation

Angular Velocity is the rate of spin of an athlete or object as they move in a particular direction

Speed of Rotation is how quickly parts of an object or athlete move in a rotational movement

Angular Velocity and Speed Angular Velocity and Speed of Rotationof Rotation

Speed of rotation of an object increases Speed of rotation of an object increases the further it is away from the axis of the further it is away from the axis of rotationrotation

Speed of rotation of an object increases Speed of rotation of an object increases the greater the angular velocitythe greater the angular velocity

Speed of rotation of an object is a product Speed of rotation of an object is a product of angular velocity and the radius ofof angular velocity and the radius of the the object from the axis of rotationobject from the axis of rotation

Force SummationForce SummationAs we know, in order to generate As we know, in order to generate momentum a force must be applied momentum a force must be applied to a bodyto a body

An athlete is able to achieve a An athlete is able to achieve a maximum velocity or force by the maximum velocity or force by the transfer of momentum through transfer of momentum through successive body part movements.successive body part movements.

HandballHandball

Shot PutShot Put

Force SummationForce SummationRule 1: Use All Body SegmentsRule 1: Use All Body Segments

To maximise muscular force we want To maximise muscular force we want to use as many body segments as to use as many body segments as possible.possible.

Force SummationForce SummationRule 2: Stretch OutRule 2: Stretch Out

Before we begin the sequence of Before we begin the sequence of body movements we should stretch body movements we should stretch muscles out to their optimal lengthmuscles out to their optimal length

to allow muscles to be contracted to allow muscles to be contracted with max force.with max force.

Force SummationForce SummationRule 3: Sequencing of Body SegmentsRule 3: Sequencing of Body Segments

Generally we move larger muscle groups Generally we move larger muscle groups first and smaller muscle groups lastfirst and smaller muscle groups last

Force generated by the larger muscle is Force generated by the larger muscle is groups passed on to the smaller onesgroups passed on to the smaller ones

Force SummationForce SummationRule 4: Timing of Body SegmentsRule 4: Timing of Body Segments

To produce max force we need to To produce max force we need to ensure that the right body segment is ensure that the right body segment is adding to the overall force at the right adding to the overall force at the right timetime

If timing is out of order movement will If timing is out of order movement will lack co-ordination and force lack co-ordination and force generation is lessened or lostgeneration is lessened or lost

Force SummationForce SummationRule 5: Full Range of MotionRule 5: Full Range of Motion

We need to move body segments We need to move body segments through the greatest range of motion through the greatest range of motion that we can.that we can.

Greater the range of motion, the Greater the range of motion, the higher the speed of the extremities higher the speed of the extremities on release/contacton release/contact