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# Biomechanical Movement Principles in SPORT

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## yostina rezk

on 11 June 2014

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#### Transcript of Biomechanical Movement Principles in SPORT

Biomechanical Movement Principles in
SPORTS

By Yostina Rezk
What is Biomechanics?
The study of the mechanics of human movement. It is the sport science field that applies the laws of mechanics and physics in human performance.
The role of Biomechanics
The general role of Biomechanics is to understand the mechanical cause -effect relationship that determine human motion. Biomechanics contribute to the description, explanation, prediction and improvement of th mechanical aspects of human movement, exercise and sports peformance.
Biomechanics are involed in:
Human performance analysis.
The analysis of force in sport and physical activity.
How injuries occur in sport.
Injury preventions and rehabilitative treatment methods.
The design and development of sport equipment.
The benifits of Biomechanics
Optimal sports performane
Injury prevntion and reduction
Higher number of participants in sports
Newton's Laws of Motion
Newton's First law of Motion:
INERTIA
'An object whether at rest or in motion will continue in that state unless it is acted upon by a force strong enough to change its state of motion or rest'
This 1st law is relevant to:
Straight line or angular motion
Levers
Inertia
Balance and stability
Newton's Second Law of Motion
ACCELERATION OR MOMENTEM
'The acceleration of an object is directly proportionate to the amount of force applied and takes place in the direction in which force is applied'
2nd Law:
Newton's Third Law of Motion
ACTION AND REACTION
'For every action there is an equal and opposite reaction'
Eg.
Rebound
Friction
Elasticity
Transfer of momentum
Straight line motion is the most basic of all motion. According to Newton's first law of motion, objects that do not experience any net force will continue to move in a straight line with a constant velocity until they are subjected to a net force. Under everyday circumstances, external forces such as gravity and friction can cause an object to change the direction of its motion, so that its motion cannot be described as linear.
Straight line Motion
Acceleration
Definition:
Rate of change of velocity over time.
Deceleration
Defintion:
A decrease in rate of change.
Velocity
Definition:
Displacement divided by the change in time.
Distance
Definition:
The path travelled by the body from Point A to Point B.
Displacement
Definition:
change of position of body
All concepts applied in sport/physical activity
Linear motion describes a situation in which movement occurs in a straight line. Linear motion can also be called translation, but only if all parts of the object or the athlete move the same distance, in the same direction, and in the same time frame.
LEVERS
Components of Levers.....
Axis/ Fulcrum
The Fulcrum is the fixed support about which the lever moves.
Force Arm
The Force Arm is the part of the lever to which some kind of force is applied.
Resistance Arm
The resistance arm is the side of the lever (from the fulcrum to the load) that carries the load.
The use of levers allows humans to apply increased force and to generate greater speed in executing sporting activities and everyday chores about home and in the workplace.
There ar 3 types of levers:
1st Class
2nd Class
3rd Class
Ist Class Levers
In a first class leaver the axis is located between the resistance and the point of force application .Ever example includes a crowbar seesaw and scissors and they are effective in magnifying the force applying.
2nd Class Lever
Second Class Levers are used to increase the strength that humans apply to objects. There levers always have the resistance or load between the axis and the force, The force arm is always longer than the resistance arm. Two everyday example are a bottle opener or a wheelbarrow.
3rd Class Lever
The lever within the body are mostly third class levers, and they have a short force arm and a long resistance arm. This leads to a speed advantage. Human movement relies on the body using third class levers.
Without levers we wouldn’t be able to use our
third class levers and bend our arms to throw
the ball or to even shoot the ball!
Without levers we wouldn’t be able to use our
second class levers and stand on our tip toes to
get those awesome jump shots!
Without levers we wouldn’t be able to use our
First class levers and nod our heads to signal and
Communicate to our team mates!

Why is the use of levers so important in a game of basketball?
The principles of conservation
The Principle of the Conservation of Momentum states that: if objects collide, the total momentum before the collision is the same as the total momentum after the collision

Transfer of momentum
Momentum is the tendency of an object to keep moving. Momentum is a vector quantity and depends on both the mass of the object and the velocity of the object
Sequential or Simultaneous force
Simultaneously:
explosive action of all body parts occurs at the same time
Eg: high jump take-off, vertical jump for rebound in basketball
Sequentially:
body parts are moved in sequence to generate a great force
Eg: throwing, striking, kicking

Force Summation
Combination of forces to produce a maximal force

Some Equipment used in Biomechanics

AMTI Force platform embedded in floor
AMTI Force platform, portable
Qualisys Motion Analysis System: 7 ProReflex cameras
Sony HD Handycam
Casio Exilim EX-FC150 High Speed Digital Camera
Treadmill, Recumbent Cycle, Monarck Cycle Ergometer

Impact is the collision between to objects. Such as in football, when one person goes for a tackle he must impact on the other person. Or the impact between the football and another contact surface, e.g. Ground or persons foot. The types of collision that occurs determines the motion of the ball after impact. E.g. If the football hits the side of your foot instead of towards the middle area it will go off more to the side.

Levers in soccer
In the case of the instep soccer kick the lever is the preferred kicking leg. The longer the lever the greater the velocity at impact and the greater the momentum developed by the object. The velocity is greater at the end of a long lever than at the end of a short lever, as the longer lever has a greater range of motion and is able to generate a greater amount of force. Therefore biomechanically a person with a longer leg (in this case the lever) should have a greater range of motion, in turn should be able to generate more force upon the ball compared to a person with a smaller lever.
PROJECTILE MOTION
Projectile motion is a form of motion in which an object or particle (called a projectile) is thrown near the earth's surface, and it moves along a curved path under the action of gravity only.
Human body as a projectile!
Magnus effect
The Magnus effect is the commonly observed effect in which a spinning ball (or cylinder) curves away from its principal flight path. It is important in many ball sports.
Tennis Spin (backspin,topspin,sidespin)
A topspin shot is hit by sliding the racquet up and over the ball as it is struck. By dragging the racquet over the ball, the friction between the racquet’s strings and the ball is used to make the ball spin forward, towards the opponent.

A backspin shot is hit in the opposite manner, by sliding the racquet underneath the ball as it is struck. This causes the ball to spin towards the player who just hit it as it travels away.

A sidespin occurs when the ball is rotating at an angle to its direction of movement.
Height of release
The height of release is the difference between the height that a prjectile is released and the height in which it lands or stops.
Velocity of release
velocity describe the rate at which a body moves from one location to another. Average speed of a body is obtained by dividing the distance by the time taken and average velocity is obtained by dividing the displacement by the time taken
e.g. a swimmer in a 50m race in a 25m length pool who completes the race in 71 seconds - distance is 50m and displacement is 0m (swimmer is back where they started) so speed is 50/71= 0.70m/s and velocity is 0/71=0 m/s
•Speed and Velocity = distance travelled ÷ time taken

Angle of projection
The angle of projection is the angle at which an object is released into the air. this angle will determine the flight path of the projectile.
Flight Path (Trajectory)
A trajectory is the path that a moving object follows through space as a function of time.
Angular Motion
Angular motion is defined as the body or object motion at a fixed axis or point like that of a pendulum or planet. The motion is equivalent to the angle passed over the axis by the line attracted to the object or body.
Torque
when you're pedaling your bike up an incline, you feel that the pedal is more difficult to push as compared to when you're riding your bike down a flat road..,,that heaviness feel on the bike pedal is a measure of the torque required to push your bike...
Angular Velocity
The rate of change of angular displacement with respect to time.
Momentum
Application to sport and physical activity
During a jump, the diver must push off the platform in a way that provides torque to change the angular momentum from zero to something greater than zero. This also gives the diver rotational motion. Now, suppose the diver wants to do a triple tuck. How can she do this in under 2 seconds? She can’t can’t change the angular momentum, but she can change the moment of inertia.By pulling the legs and arms closer to the point of rotation, the moment of inertia decreases and the angular velocity increases. A tighter tuck means a faster rotation. But how does she stop rotating to enter the water? She doesn’t because she can’t. The best she can do is increase the moment of inertia again to decrease the angular speed. Yes, it’s a tough move, but that’s why they’re Olympic divers.
The Coefficient Of Restitution
The Coefficient Of Restitution (COR) measures the elasticity of a pair of objects in collision and is the ratio of their final relative speed to their initial relative speed. Determined through experimentation, this coefficient essentially measures bounciness. If the coefficient is close to one, then the collision is elastic and bouncy, if it is close to zero then collision is more plastic. Most professional sports have specific guidelines for the coefficient of restitution of equipment, such as balls, clubs and rackets.
Accuracy
Sports whose objective is to hit a target of various shapes and sizes (such as a pocket, hole, jack or bowling pin) using various means (such as a bow, firearm, billiard cue, ball or club).

Flattening the arc

A movement pattern of the arm, which improves accuracy when throwing or hitting a projectile. It involves flattening the centre of the arc of the curve in which the arm is travelling and in the direction in which the projectile is to follow.

Centre of gravity in sports
Every single body and thus the athletes themselves, is made up of individual components each of which has its own weight. So our weight is just the sum of individual weights, of components such as our arms, legs, etc. The point, about which the distribution of these individual weights is symmetrical, is the center of gravity of the body. Thus, if a body has more mass distributed in its upper part, the center of gravity will be closer to the top of the body. This applies to humans, as the center of gravity of an average person is located approximately at a height of one meter, thus being above the waist.

Mass in sports
the amount of matter tha maks up an object, The greater the mas of an object or body, the greter the force requred to move it, and therefor disrupt is equilibrium.
Stability and Balance
Equilirium, stability and balance are concepts that are all closely related. Stability is te resistance to the disruption of equilibrium and balance is the ability to control equilibrium.
Factors affecting Stability are:
Body mass
friction between the body an the surface
base support
position of te centr of gravity
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