Levers

Levers are used to make things easier for us to do.

When we exercise most of our movements will involve the use of levers. A lever system within the body would use a bone to move an object.

All lever systems are made up of four components:

the load
the fulcrum
the effort
the lever

Muscles are attached to bones via tendons and the bones of the skeleton act as levers which muscles pull on to create movement.

In the human body, the lever is usually a bone, the effort is provided by the muscle (the muscles point of application/insertion), the load is the weight of the body and any additional resistance and the fulcrum is the joint itself.

The greater the ratio of the effort arm to the load arm, the more efficient the lever system is (i.e. the easier it is to move the load).

Therefore, if the distance between a muscle's insertion site and the joint is greater than the distance between the load and the joint, your muscle is at an advantage.

This is why your gastrocnemius can lift more weight than your bicep, even if they are equally as strong!

CLASSES OF LEVER

For 1, 2, 3 think F, L, E" This rhyme helps us to identify the middle component of each system

First-class lever, F is the middle component.
Second class lever, L is the middle component.
Third-class lever, E is the middle component.

FIRST CLASS LEVER

SECOND CLASS LEVER- the most mechanical advantage in the body

THIRD CLASS LEVER- the most abundant in the body

ACTIVITY:

Skilled performance is made possible through the effective use of lever systems.

a) Sketch and label a third-class lever system.

b) In your diagram, draw and label the effort arm and the resistance arm.

c) What are the advantages and disadvantages of third-class levers over the other types of lever systems?

ANSWER

DOWNLOAD Lever...swer.pdf

The efficiency of a lever relies on the ratio of the effort/force arm to the load arm.

The effort arm (EA) is the distance between the fulcrum and the effort; in the body, this is the distance between the joint and the muscle's insertion site.

The load arm (LA) is the distance between the fulcrum and the load; in the body, this is the distance between the joint and the loaded body part.

MECHANICAL ADVANTAGE

The ratio of load to effort is known as the mechanical advantage (MA).

MA = (F output) / ( F input )

LONGER LEVERS RESULT IN GREATER SPEED

good for throwing and striking

SHORTER LEVERS RESULT IN GREATER STRENGTH

good for pulling, pushing and lifting