# Forces are the basis for all movement.

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Forces are the basis for all movement.
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.

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. Gravity. Air resistance. Speed of release. Angle of release. Height of release. 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?

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.

Can you give me an example?
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 inter-relationship 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
As the height of release increases, the angle of release decreases. As the height of release decreases, the angle of release increases. 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. Range is decreased with topspin. 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 net-making it harder for teams to return.

The weight that needs to be moved.
levers A lever is used when you want to apply more force. Most levers have three clearly identified parts: 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: FIRST CLASS SECOND CLASS 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: The fulcrum – the pivot point around which the movement happens. In body levers this is usually the joint. The load – the weight that needs to be moved (resistance). 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.