Levers in Physiotherapy

Body Levers

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 fixed point called fulcrum( F ). It is simple machine which magnifies the force 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 energy is applied to the rigid bar. EF RF F EA RA

4. 4 LEVERS Resistance Arm – Resistance ( R ) is the point where object is held. RA includes all parts of the rigid mass between the fulcrum and the point at which energy is applied to the object to be moved by the lever.

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 : First Class Lever Second Class Lever Third Class Lever

7. 7 LEVERS First Class Lever EA RA F EA RA In this F lies in between the point of application 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 posterior neck muscle applied at their attachment to occipital bone.

9. 9 LEVERS Second Class Lever In this the RF has a point of application between 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 raised to stand on toes Tarsal & Metatarsal bones form lever Fulcrum Metatarsophalangeal joints. Weight of the body transmitted through the ankle 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 between 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 hand Effort by the contraction of biceps muscle applied at its insertion.

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 magnitude of resistance. I.e smaller effort is required to overcome a large resistance.

14. 14 LEVERS In all 2 nd class lever, the MA of the lever is greater than than one as EA > RA . In our body majority are 3 rd class levers. Mechanical advantage < 1.

15. 15 LEVERS Uses of Lever By learning the concepts of various types of lever these principles can be applied in almost all aspects of therapy. To make exercise more resistive long lever arm can be selected. Contrary in the beginning short lever arm is preferred.

16. 29 LEVERS THANK YOU FOR YOUR KIND ATTENTION