Lever system - Definition, their types and lever work in body

1. LEVER
By :
RohiniSurti
BPT 2ndYEAR

2. DEFINITION :
A lever system is a rigid bar that moves on a fixed
point called the fulcrum when force is applied to it.
 A lever system is made of three parts,they are
1.EFFORTS
2.LOAD
3.FULCRUM.

3.  Efforts arm:The Perpendiculardistance from
the fulcrumTo the efforts.
Is provided by muscles.
 Load arm:The distance from the fulcrum to
the weight of the body
It is provided by the weight of the body and
resistance applied.
 Fulcrum is joint of the body.
Forfirsts,Second,Third order lever the middle componentis ; ( Code :FLE)
Firsts Order:Fulcrum
SecondOrder:Load
Third Order:Efforts.

4. FUNCTIONS:
1.It increase the resistance than
given force can move.
2.It increase the speed at which
body moves.

5. FIRST
CLASS
LEVER
SYSTEM:
 In first class lever system, the fulcrum is between
the efforts and the weight of the body.
 Therefore, the efforts and weight arms May be
equal or one may exceed the other in length.
 Example :Demonstrated during nodding
movement of the head.
 the skull represents the lever, the Atlanto-occipital
bone joints the fulcrum, the weight is situated
anteriorly in the face and efforts is supplied by the
contraction of the posterior neck muscles.

6. First class lever
seen during
nodding
movement of
head.

7. SECOND
CLASS
LEVER
SYSTEM :
 In secondclasslever system, the weight is between
the fulcrum and the efforts.
 The efforts arm must therefore alwaysexceed the
weights arm.
 Example:During Plantarflexion,the heels are raised to
stand on the toes.
 The tarsal and metatarsal bones are stabilisedby
muscular action to form lever.
 The fulcrum is at metatarsophalangealjointand the
weight of the bodyis transmitted through the ankle
joint to the talus.
 The efforts is given by contractionsof calfmuscles.

8. Second class
lever seen During
Plantarflexion of
foot

9. THIRD
CLASS
LEVER
SYSTEM :
 In third class lever system, the efforts is between
the fulcrum and the weight.
 The weights must therefore exceed the efforts arm.
 Example:Elbow joint
when lever is forearm , the Fulcrum is elbow joint and
effort is supplied by the contraction of the brachial is
muscles applied at its insertion.
The weight is some object hold in the hand.

10. Third class
lever system
seen in
elbow joint.

11. THANKYOU

12. REFERENCE:
M. DENAGARDINER–THE PRINCIPLESOF
EXERCISETHERAPY.