Levers

For your arm, leg or any body part to move the appropriate muscles and bones must work together as a series of levers. A lever comprises of three components -

Fulcrum, pivot point, or access of rotation - the point about which the lever rotates
Load - the force applied by the lever system
Effort - the force applied by the user of the lever system

The way in which a lever will operate is dependent on the type of lever.

Classification of Levers

Class 1 - The fulcrum lies between the effort and the load
Class 2 - The fulcrum is at one end, the effort at the other end and the load lies between the effort and the fulcrum
Class 3 - The fulcrum is at one end, the load at the other end and the effort lies between the load and the fulcrum

Class 1 Lever

Class 2 Lever

Class 3 Lever

Class 3 is the most common class of lever to be found in the human body.

Examples in strength training

Class 1 - Seated dumbbell triceps extension (the load is held in the hand and the triceps produces the effort force)
Class 2 - Standing heel lift (the load is held in the hands or placed across the shoulders and the gastrocnemius or calf muscle produces the effort force)
Class 3 - Seated biceps curl (the load is held in the hand and the biceps produces the effort force)

Class 1 Lever in the Body

Class 2 Lever in the Body

Class 3 Lever in the Body