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Levers - Coggle Diagram
Levers
Second class levers
The components of the second class lever system are arranged as shown in Figure 7.3. What component is at the centre of this lever system? Again there are limited examples of these lever systems in the body
The one with possibly the greatest application for sport is the second class lever system formed between the ball of the foot, the gastrocnemius and the load of the bodyweight as we point our toes, or go onto our toes (the foot is the lever bar)
Systems in the body
A lever system within the body would use a lever (bone) to move an object, for example, when we run we are the object being moved, but when kicking a ball, the object being moved is the ball.
The load is the object requiring moving, the effort is the muscular force we use to move the object, the fulcrum is the joint around which the movement occurs and the bones of the skeleton are the levers.
A tree would be too heavy to lift, but a person could move the tree a little by using a lever system
First class levers
Example A (see p xx) of the fallen tree would use a first class lever system: the tree would be the load, the end of the wooden bar under the tree would be the fulcrum and the effort would be the muscular force applied to the other end of the wooden bar.
First class lever systems are arranged so that the fulcrum is between the effort and the load (see Figure 7.2). This is the arrangement of a first class lever system.
Nodding of the head is another example of a first class lever system, important in sport when watching the flight of a ball for example; in this example the load would be the weight of the head.
For example, due to where the triceps attach to the elbow joint, elbow extension is considered to be use of a first class lever system.
Chapter 7 Movement analysis – lever systems in sport and physical activity 51 There are a limited number of examples of first class lever systems in the body.
Further explanation of this can be left for level 3 Sport or PE courses; it is sufficient for you to appreciate that elbow extension involves a first class lever.
Third class levers
You can tell when it's a first class lever system as the fulcrum is in-between the other components; in the second class it is the load and in the third it is the effort.
The final class of lever is shown in Figure 7.4. What is the component in the middle of this lever system? One way to remember the difference between each system is to remember the component in the middle of each one
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Major body axes
For example, when we talked of a biceps curl involving flexion and extension in the sagittal plane we know this movement is only possible because of the elbow joint.
Therefore, in order for these movements to take place there has to be an axis (which goes through a joint) for the bones of the skeleton to move about.
We know from Chapter 1 that in order for our bones to move, movement has to take place around a joint.
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