This document discusses mechanical advantage in exercise and describes the three classes of levers. It defines key terms like moment, moment arm, force couple, and mechanical advantage. It explains that first class levers have the fulcrum between the input and output forces, second class levers have the output between the fulcrum and input, and third class levers have the input between the fulcrum and output. Most skeletal muscles act as third class levers, allowing for rapid movement with little muscle shortening. The document also covers centripetal force.

1. Mechanical Advantage in
Exercise

2. Moment of Force
(torque) the product of the
force magnitude and its
perpendicular distance from
the point of force to the axis of
rotation. This can be
increased or decreased by
changing the amount of force
applied, or changing the
distance from the axis that the
force is applied.
The turning effect of a force is
known as the moment. It is the
product of the force multiplied by
the perpendicular distance from
the line of action of the force to
the pivot or point where the object
will turn.

3. Moment Arm
The perpendicular distance
from either the point of force
or point of resistance to the
axis.
A moment arm is simply the
length between a joint axis
and the line of force acting on
that joint. Every joint that is
involved in an exercise has a
moment arm. The longer the
moment arm is the more load
will be applied to the joint axis
through leverage

4. Force Couple
when equal parallel forces act
in the opposite direction. e.g.
the internal and external
obliques working together. e.g.
the serratus anterior and
upper trapezius work together
in upward rotation of the
scapulae.
In mechanics, a couple refers
to two parallel forces that are
equal in magnitude, opposite
in sense and do not share a
line of action

5. Force Couple
Its effect is to create rotation
without translation, or more
generally without any
acceleration of the centre of
mass. In rigid body
mechanics, force couples are
free vectors, meaning their
effects on a body are
independent of the point of
application
The resultant moment of a
couple is called a torque. This
is not to be confused with the
term torque as it is used in
physics, where it is merely a
synonym of moment. Instead,
torque is a special case of
moment. Torque has special
properties that moment does
not have, in particular the
property of being independent
of reference point

6. 4 Main functions of levers
1) Gain Mechanical force advantage
2) Gain advantage in speed/ROM
3) Balance forces
4) Change direction of an applied force
Lever
Rigid structure revolving around
a fulcrum
1) Effort (motive forces)
2) Resistance force

7. Mechanical Advantage
The ratio of the output force
developed by a muscle to the
input force applied to the body
structure that the muscle
moves. Variations in the sizes
of muscles and the lengths of
bones in different individuals
partially account for the
differences in mechanical
advantage and physical
capabilities, such as speed and
strength, among body types.
There are three parts to all
levers:
• Fulcrum - the point at which
the lever rotates.
• Input force (also called the
effort) - the force applied to the
lever.
• Output force (also called the
load) - the force applied by the
lever to move the load.

8. Mechanical Advantage
A lever allows a given effort to
move a heavier load, or to
move a load farther and faster,
than it otherwise could. If the
load is close to the fulcrum
and the effort is applied far
from the fulcrum, a small
effort exerted over a relatively
large distance can move a
large load over a small
distance. Such a lever is said
to operate at a mechanical
advantage and is commonly
called a power lever
the load is far from the
fulcrum and the effort is
applied near the fulcrum, the
force exerted by the muscle
must be greater than the load
to be moved or supported. This
lever system is a speed lever
and operates at a mechanical
disadvantage

9. In a second-class lever, the
effort is applied at one end of the
lever and the fulcrum is located at
the other, with the load between
them. A wheelbarrow demonstrates
this type of lever system. Second-
class levers are uncommon in the
body, but the best example is the act
of standing on your toes. All second-
class levers in the body work at a
mechanical advantage because the
muscle insertion is always farther
from the fulcrum than the load..
Second-class levers are levers of
strength, but speed and range of
motion are sacrificed for that
strength

10. In a third-class lever, the
effort is applied between the
load and the fulcrum. These
levers are speedy and always
operate at a mechanical
disadvantage – think of
tweezers and forceps. Most
skeletal muscles of the body
act in third-class lever
systems. An example is the
activity of the biceps muscle of
the arm, lifting the distal
forearm and anything carried
in the hand.
Third-class lever systems permit
a muscle to be inserted very close
to the joint across which
movement occurs, which allows
rapid, extensive movements (as in
throwing) with relatively little
shortening of the muscle.
Muscles involved in third-class
levers tend to be thicker and
more powerful

11. There are three parts to all
levers:
• Fulcrum - the point at which
the lever rotates.
• Input force (also called the
effort) - the force applied to
the lever.
• Output force (also called the
load) - the force applied by the
lever to move the load.

12. In a first class lever, the
fulcrum is located between the
input force and output force

13. In a second class lever, the
output force is between the
fulcrum and the input force.

14. In a third class lever, the
input force is between the
fulcrum and the output force.
.

15. Centripetal Force
Center seeking force. That
force applied to the lever by
the axis which is pulling the
radius toward the axis
Center fleeing force That force
which constantly is trying to
make the radius leave the
circular pathway of motion and
fly off at a tangent to the circle.

16. Centripetal Force
Centripetal force is the case in
which a body moves with
uniform speed along a
circular path
The centripetal force is
directed at right angles to the
motion and also along the
radius towards the centre of
the circular path
Several principles can affect
Centripetal or Centrifugal
Force.
1. If the mass of the object is doubled
the centripetal force will double.
2. If we double the radius the
centripetal force is decreased by 1/2.
3. If we double the velocity the
centripetal force increases by 4 times.
4. If we decrease the velocity by 1/2 the
centripetal force decreases to 1/4.