Presentation of lever by Rahul Sharma.pptx

This presentation is about lever and it's types and about its function

1. Lever By: Rahul Sharma Submitted to : Dr. Aditi Buliya (PT)

2. Lever Lever is a rigid bar that rotates around fixed point called fulcrum (F) It is simple machine which magnifies the force and speed of movement

3. Components 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 a 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

4. 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. Lever in Human Body Fulcrum  Joint Effort Force  Muscle Force Resistance Force  Gravity/weight

6. Types of lever Mainly three :- First order lever Second order lever Third order lever

7. First order lever In this F lies in between the point of application of Effort and the point of application of Resistance.

8. 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. Second order lever In this the RF has a point of application between the F and the point of application of the EF. (EA>RA)

10. Example of Second Order 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. Third Order Lever In this the EF has a point of application between the F and the point of application of the RF. (RA>EA)

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

14. 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 lever arm can be selected. Contrary in the beginning short lever arm is preferred.

15. THANKYOU