Mechanical Principles Aim of the lesson: To develop an understanding of the following mechanical principles: Balance (Centre of Gravity) Transfer of weight Application of force Rotation Resistance Follow through

Balance (Centre of Gravity) Balance is the ability to retain the centre of gravity over your base of support Static Balance for example a headstand require you to hold a balance still Dynamic balance requires you to maintain balance under constantly changing conditions. For example when skiing you constantly adjust your dynamic balance as you travel over changing terrain in order to remain balanced. Can you think of another example of static balance and dynamic balance.

Stability The larger your base of support and the lower you base support the more stable you are Think of a gymnast performing a headstand and a handstand which would be the most stable position and why? Body tension is also important when performing a balance Headstand- The gymnasts base of support is lower and her base is wider than the gymnast doing the handstand.

Transfer of weight Transfer of weight is shifting your weight from one body part to another. In pairs think of two Skills/techniques where you need to transfer your weight from one part of the body to the other. How well you transfer your weight depends on how well balanced you are. Some skills and techniques require a single transfer of weight for example a javelin throw while others require a repeated transfer of weight for example running. Again in two’s can you list skills /techniques that require a single transfer of weight and ones which require a repeated transfer of weight. Discuss single transfer of weight and repeated transfer of weight. Balance and transfer. Discuss overhead clear if not balanced then less power and accuracy in shot.

Application of Force Newton’s Third Law: For every action there is an equal and opposite reaction Speed and power are important when applying a force as well as the direction of the force. Have a look at the rugby scrum. Which direction are the team on the left applying the force. Which direction does that cause them to move? Now have a look at the person in the Kayak. Which direction is the person applying the force with the paddle and which direction are they therefore moving in? To help performers resist the forces involved in completing different actions various types of equipment are used. Sprinters use starting blocks, outdoor games players use studded boots to provide grip and RESSITANCE. By contrast. Shot putters use chalk dust to REDUCE FRICTION between the throwing hand and the shots so that the throw can be more easily completed. CREDIT EXTENSION: If speed is required then the greater the force applied the better. Differences in the mass of the body will affect performance. If the force applied to the sprinting block is the same the athlete with the smaller mass will accelerate at a quicker rate.

Rotation In different activities you rotate (turn) in order to carry effective skills and techniques. When throwing the discus in athletics you turn around in a sprinting back-to –front movement to generate power. This is a complex technique. You build up speed before throwing , by quickly turning your feet around. After the throw you follow through and keep turning until you have regained your balance. As well as rotating around you can also rotate by turning head over heels. This is part of completing a front somersault. Another form of rotation is when you turn sideways. A cartwheel, where you turn over from feet to hand balancing on ground before returning to feet on the ground, is an example of this type of rotation. The tighter you tuck the faster you rotate. E.g. Front sommersault

Resistance Resistance can either been advantage or a disadvantage. Advantages: When sprinting in Athletics the starting blocks are an advantage. They provide a resistance. By powerfully straightening the legs against the starting blocks the sprinter can quickly gain speed. Disadvantage: If you are running into a headwind this would be a disadvantage. Think of other activities where resistance can be an advantage and disadvantage. Sprinter: The track creates a helpful resistance as you continue running. If you are running into a headwind this would be unhelpful.

Follow through Follow through is the part of the action which occurs after the ball/shuttle cock etc has been struck/released. Follow through helps the following It can improve accuracy It can increase the power/strength/distance of throw It can help you keep balanced It can help prevent injury.