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Lever systems Typeit
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In human bodies, levers are used to create movement around a joint. They are made up of three components:
-class levers have the fulcrum placed in the middle between the effort and resistance/load. Take a javelin thrower who is about to extend their elbow in preparation to throw. The resistance is the weight of the javelin; the fulcrum point is the athletes elbow; and the effort is the athletes triceps contracting, pulling downwards. Movements of these systems can be balanced and allow a wider range of movement than a -class lever.
-class lever systems have the fulcrum at one end of the lever; the effort at the opposite end of the lever; and the load/resistance in between. When someone performs plantar flexion, they are using this class of lever system. The fulcrum is located at the ball of the foot, with the resistance being the mass of the body pulling downwards, due to gravity. The effort comes from the muscle, pulling on the foot to point the toes downwards. This lever system can move a load with a small , but it can only move the large load over a small range of movement.
-class lever systems have the fulcrum at one end of the lever; the load at the opposite end of the lever; and the effort in the middle. When someone performs a biceps curl, flexing the elbow, they are using this class of lever system. The fulcrum is at the joint; the resistance is located at the hand/weight; and the effort originates at the muscle, lifting the lower arm. Movement can be completed quickly over a large range of motion.
In levers, different systems have different advantages. This helps an element of movement within that particular lever system and can be calculated by dividing the effort arm length by the resistance arm length: