Principles of Functional Exercise

The first class of lever is depicted by the effort and resistance or load on opposite sides
of the fulcrum as shown in Figure 2. An example of this in the human body is the triceps brachii
during a triceps push-down.

Figure 2. Example of a Class I lever

Class II levers
A second class lever is classified when the effort and resistance/load act on the same
side of the fulcrum, with the muscle contracting through a moment arm longer than that of the
resistance moment arm, as shown in Figure 3. In other words, the resistance/load is between
the axis of rotation and the force or effort. The effort needed to move the lever is much less from
the muscle contraction because the moment arm is longer, and the load is much easier to lift.
This lever is the most efficient machine in the human body, but there are minimal areas where
it is used. An example of this is the triceps and gastroc-soleus complex. This occurs when the

forefoot is on the ground and the heel is being lifted.
Figure 3. An example of a Class II lever