for physiotherapy students

1. Lever
 BY : DR.BHARTI SUBHASH PAWAR (PT)

2. LEVER,
A lever is defined as the rigid bar , which moves about on some fixed
point called “FULCRUM”.
FULCRUM

3. To perform an activity or a movement ,the bone act as the lever and joints acts as the
fulcrum.
The movement will be created by two types of forces, i.e. resistance (R), and effort(E), in which the
resistance (R) is the opposing force and the effort (E) is action achieving force.
Effort Arm :
• The perpendicular distance from fulcrum to effort is called EA .
• 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 .
Resistance arm :
• The perpendicular distance from fulcrum to the weight is called RA or
WA
• 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.  Levers in human body
 Fulcrum -----joint
 Effort force -----muscle force
 Resistance force -------gravity /weight

6.  Types of Levers .
 These are of three types.
 1. First order lever (1°)
 2. Second order lever (2°)
 3. Third order lever (3°).

7.  I st Order Lever:
 Ex: Nodding movements of
head.
 Skull represents lever
 Atlanto-occipital joints
represents fulcrum,
 The weight is situated
anteriorly in the face and
 The effort is supplied by
contraction of posterior neck
muscles

8.  2nd Order Lever:
 Ex: Rising of heels to stand on toes Tarsal
and metatarsal bones are stabilized to
form lever.
 Fulcrum is metatarsophalangeal joint
 weight of the body is transmitted to
ankle joint by talus.
 Effort is applied by combination of calf
muscles.

9.  3rd Order Lever:
 Ex:
 When lever is forearm,
 Fulcrum is elbow joint effort is
supplied by contraction of brachialis
muscle and
 weight is some object held in hand.

11. • EXERCISE THERAPY MECHANICAL ADVANTAGE:
• Efficacy of force in relation to lever depends on two factors.
• They are
• i) Force exerted (W) or (E)
• ii) Perpendicular distance from fulcrum to the weight’s arm or efforts arm. –
• When both weights arm and efforts arm are of equal length no advantage is
gained.
• - However if the length of effort arm exceeds weight arm an advantage will be
gained by the use of lever. This is known as Mechanical advantage. –
• Here less effort is required to lift a weight.
• Mechanical advantage is obtained in 1st order lever when fulcrum is nearer to
weight than to effort, and in all levers of the 2nd order. It is never obtained in
3rd order lever. - It is the ratio of weight to effort.
• M.A = W/E

15. Thank you !