How Does the Elbow Work: A Lesson in Levers

 Author:  Lucas Delezene

AreaLife Sciences 

 Grade Level: 10-12


There are three basic categories of levers that exist in the human body. These lever classes differ in how they function mechanically. This lesson examines third class levers in the body and demonstrates that in fact there is a consistent pattern of reducing the mechanical advantage of third class levers in the body. The role of third class levers in the body is examined by modeling the elbow. The elbow consists of the articulation between three bones: the humerus, the radius, and the ulna. When you bring your hand closer to your shoulder, this is a movement known as flexion. Flexion at the elbow is caused primarily by the biceps brachii as long as your palm is facing up. So in this example the elbow acts as the fulcrum of the lever and the biceps acts as the force being applied to the lever. The elbow is a type of third class lever. Other examples of a third class levers are a crane and a drawbridge.


National Standards:

Physical Sciences: Content Standard B

  • Motions and forces

Life Sciences: Content Standard C

  • Structure and function in living systems

AZ State Standards:

Strand 5: Physical Sciences

Concept 2 Motions and Forces



 Keywords: levers, human body, elbow, mechanical advantage


Lesson Plan (pdf / doc)
Levers and the Body (pdf / doc)