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1.1.c. Movement analysis (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:
- – this is the point at which a lever is balanced, or around which rotation occurs.
- – this is the point and direction of a force applied to the lever system.
- – this is the force acting against the effort.
-class levers have the fulcrum placed in the middle, between the effort and resistance/load. An example of this lever system is an offensive header in football, where the resistance is the weight of the ball and the head, the fulcrum is located at the joints in the neck, and the effort is the contraction of the muscles in the neck, pulling the head forwards and downwards to meet the ball. Movements that use this type of system can be balanced and allow a wider range of movement than with 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 (i.e. points their toes), they are using this class of lever system. The fulcrum is located at the ball of the foot, with the resistance/load being the mass of the body pulling downwards, due to gravity. The effort comes from the muscle pulling on the bones it attaches to at the heel, via the Achilles tendon. This lever system can move a load with a relatively small amount of , but it can only move the 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:
- Resistance arm – the distance between the and the resistance/load
- Effort arm – the distance between the fulcrum and the