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1
LEVERS
LEVERS
DEFINATION
 COMPONENTS OF LEVER
TYPES OF LEVER
EXAMPLES
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
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
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
LEVERS
Levers in Human Body
Fulcrum
Effort Force
Resistance Force
Muscle Force
Joint
Gravity/Weight
6
LEVERS
TYPES OF LEVER
 Mainly three:
1.First Class Lever
2.Second Class Lever
3.Third Class Lever
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
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
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
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
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
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
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
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
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.
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
Levers in Physiotherapy
29
LEVERS
THANK YOU
FOR
YOUR KIND
ATTENTION

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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.