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 :-
1. First order lever
2. Second order lever
3. 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 2nd order lever, the MA of the lever is greater
than one as EA > RA.
• In our body majority are 3rd 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.

16. THANK
YOU