Mechanical Principles

Aim of the lesson: To develop an understanding of the Aim of the lesson: To develop an understanding of the following mechanical principles:following mechanical principles:

Balance (Centre of Gravity)Balance (Centre of Gravity) Transfer of weightTransfer of weight Application of forceApplication of force RotationRotation ResistanceResistance Follow throughFollow through

Balance (Centre of Gravity) Balance is the ability to retain the Balance is the ability to retain the

centre of gravity over your base of centre of gravity over your base of supportsupport

Static Balance for example a Static Balance for example a headstand require you to hold a headstand require you to hold a balance stillbalance still

Dynamic balance requires you to Dynamic balance requires you to maintain balance under constantly maintain balance under constantly changing conditions. For example changing conditions. For example when skiing you constantly adjust when skiing you constantly adjust your dynamic balance as you travel your dynamic balance as you travel over changing terrain in order to over changing terrain in order to remain balanced.remain balanced.

Can you think of another example Can you think of another example of static balance and dynamic of static balance and dynamic balance.balance.

Stability

The larger your base of support The larger your base of support and the lower you base support and the lower you base support the more stable you arethe more stable you are

Think of a gymnast performing Think of a gymnast performing a headstand and a handstand a headstand and a handstand which would be the most stable which would be the most stable position and why?position and why?

Body tension is also important Body tension is also important when performing a balancewhen performing a balance

Transfer of weight Transfer of weight is shifting your Transfer of weight is shifting your

weight from one body part to another.weight from one body part to another. In pairs think of two Skills/techniques In pairs think of two Skills/techniques

where you need to transfer your weight where you need to transfer your weight from one part of the body to the other.from one part of the body to the other.

How well you transfer your weight How well you transfer your weight depends on how well balanced you are.depends on how well balanced you are.

Some skills and techniques require a Some skills and techniques require a single transfer of weight for example a single transfer of weight for example a javelin throw while others require a javelin throw while others require a repeated transfer of weight for example repeated transfer of weight for example running. running.

Again in two’s can you list skills Again in two’s can you list skills /techniques that require a single transfer /techniques that require a single transfer of weight and ones which require a of weight and ones which require a repeated transfer of weight.repeated transfer of weight.

Application of Force Newton’s Third Law: For every action Newton’s Third Law: For every action

there is an equal and opposite reactionthere is an equal and opposite reaction Speed and power are important when Speed and power are important when

applying a force as well as the direction applying a force as well as the direction of the force.of the force.

Have a look at the rugby scrum. Which Have a look at the rugby scrum. Which direction are the team on the left direction are the team on the left applying the force. Which direction applying the force. Which direction does that cause them to move?does that cause them to move?

Now have a look at the person in the Now have a look at the person in the Kayak. Which direction is the person Kayak. Which direction is the person applying the force with the paddle and applying the force with the paddle and which direction are they therefore which direction are they therefore moving in?moving in?

Rotation In different activities you rotate (turn) in In different activities you rotate (turn) in

order to carry effective skills and techniques. order to carry effective skills and techniques. When throwing the discus in athletics you When throwing the discus in athletics you turn around in a sprinting back-to –front turn around in a sprinting back-to –front movement to generate power. This is a movement to generate power. This is a complex technique. You build up speed complex technique. You build up speed before throwing , by quickly turning your before throwing , by quickly turning your feet around. After the throw you follow feet around. After the throw you follow through and keep turning until you have through and keep turning until you have regained your balance.regained your balance.

As well as rotating around you can also rotate As well as rotating around you can also rotate by turning head over heels. This is part of by turning head over heels. This is part of completing a front somersault. Another form completing a front somersault. Another form of rotation is when you turn sideways. A of rotation is when you turn sideways. A cartwheel, where you turn over from feet to cartwheel, where you turn over from feet to hand balancing on ground before returning to hand balancing on ground before returning to feet on the ground, is an example of this type feet on the ground, is an example of this type of rotation.of rotation.

Resistance Resistance can either been Resistance can either been

advantage or a disadvantage.advantage or a disadvantage. Advantages: When sprinting in Advantages: When sprinting in

Athletics the starting blocks are an Athletics the starting blocks are an advantage. They provide a advantage. They provide a resistance. By powerfully resistance. By powerfully straightening the legs against the straightening the legs against the starting blocks the sprinter can starting blocks the sprinter can quickly gain speed. quickly gain speed.

Disadvantage: If you are running Disadvantage: If you are running into a headwind this would be a into a headwind this would be a disadvantage.disadvantage.

Think of other activities where Think of other activities where resistance can be an advantage and resistance can be an advantage and disadvantage.disadvantage.

Follow through Follow through is the part of the Follow through is the part of the

action which occurs after the action which occurs after the ball/shuttle cock etc has been ball/shuttle cock etc has been struck/released.struck/released.

Follow through helps the followingFollow through helps the following It can improve accuracyIt can improve accuracy It can increase the It can increase the

power/strength/distance of throwpower/strength/distance of throw It can help you keep balancedIt can help you keep balanced It can help prevent injury.It can help prevent injury.