Levers in Physiotherapy
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1. A lever is a rigid bar that rotates around a fixed point called a fulcrum and is a simple machine that magnifies force and movement speed. 2. The three main components of a lever are the fulcrum, the effort arm where force is applied, and the resistance arm where the object to be moved is located. 3. There are three types of levers - first class levers have the fulcrum between the effort and resistance arms, second class levers have the resistance arm between the fulcrum and effort arm, and third class levers have the effort arm between the fulcrum and resistance arm.
Levers in Physiotherapy
- 1. 1 LEVERS LEVERS DEFINATION COMPONENTS OF LEVER TYPES OF LEVER EXAMPLES
- 2. 2 LEVERS LEVER LEVER is a rigid bar that rotates around a fix ed point called fulcrum(F). It is simple machine which magnifies the for ce and speed of movement. Rigid Bar Fulcrum
- 3. 3 LEVERS Component of Lever Fulcrum It is represented by the joint or is a point on the axis about which the rigid mass rotates. Effort Arm Effort (E) is the point where muscle is attached to the bone. It includes all parts of the rigid mass between the fulcrum and the point at which en ergy is applied to the rigid bar. EF RF F EA RA
- 4. 4 LEVERS Resistance Arm Resistance ( R ) is the poin t where object is held. RA includes all parts of the rigid mass betwe en the fulcrum and the point at which energy is applied to the object to be moved by the le ver.
- 5. 5 LEVERS Levers in Human Body Fulcrum Effort Force Resistance Force Muscle Force Joint Gravity/Weight
- 6. 6 LEVERS TYPES OF LEVER Mainly three: 1.First Class Lever 2.Second Class Lever 3.Third Class Lever
- 7. 7 LEVERS First Class Lever EA RA F EA RA In this F lies in between the point of applic ation of Effort and the point of application of Resistance.
- 8. 8 LEVERS Example of First Class Lever Skull represents the first class lever. Fulcrum Atlanto occipital joint Weight situated anteriorly in the face. Effort is supplied by contraction of posterio r neck muscle applied at their attach ment to occipital bone.
- 9. 9 LEVERS Second Class Lever In this the RF has a point of application betw een the F and the point of application of the EF. (EA>RA) EF RF F EA RA
- 10. 10 LEVERS Example of Second Class Lever In the lower limb when the heels are r aised to stand on toes Tarsal & Metatarsal bones form lever Fulcrum Metatarsophalangeal joints. Weight of the body transmitted through the an kle joint to talus. Effort at the insertion of tendo-calcaneum by the contraction of calf muscle.
- 11. 11 LEVERS Third Class Lever In this the EF has a point of application betw een the F and the point of application of the RF. (RA>EA) EF RF F EA RA
- 12. 12 LEVERS Example of Third Class Lever When lever is the forearm. Fulcrum Elbow joint Weight Some object held in the ha nd Effort by the contraction of bicep s muscle applied at its inser tion.
- 13. 13 LEVERS MECHANICAL ADVANTAGE ( M Ad) It is a measure of the efficiency of the lever. M Ad = EA / RA Whenever MA is > than one, the magnitude of the effort force can be smaller than the ma gnitude of resistance. I.e smaller effort is req uired to overcome a large resistance.
- 14. 14 LEVERS In all 2nd class lever, the MA of the lever is g reater than than one as EA > RA. In our body majority are 3rd class levers. Mechanical advantage < 1.
- 15. 15 LEVERS Uses of Lever By learning the concepts of various type s of lever these principles can be applied in almost all aspects of therapy. To make exercise more resistive long le ver arm can be selected. Contrary in the beginning short lever arm is preferred.