Levers

Levers in our body are formed from bones, joints and muscles.

A lever consists of:

  • a rigid structure (bone)
  • a force acting upon it (muscle) to produce a turning movement (angular motion)
  • a fulcrum which is a fixed point (joint)
  • a load or resistance that is placed on the rigid structure (weight of body part being moved and anything that it is carrying)
Lever in the human body, consisting of a load represented by a weight, effort acting on the lever, and a fulcrum at a joint or fixed point.A typical lever

There are three types of lever.

1. First class lever – the fulcrum is in the middle of the effort and the load.

The fulcrum is in the middle of the effort and the load, as exemplified in the neck when nodding the head.First class lever

This type of lever is found in the neck when raising your head to head a football. The neck muscles provide the effort, the neck is the fulcrum, and the weight of the head is the load.

2. Second class lever – the load is in the middle between the fulcrum and the effort.

The load is in the middle of the fulcrum and the effort, as exemplified in the ankle when standing on tiptoe.Second class lever

This type of lever is found in the ankle area. When standing on tiptoe, the ball of the foot acts as the fulcrum, the weight of the body acts as the load and the effort comes from the contraction of the gastrocnemius muscle. This second class lever is used when taking off for a jump or pushing against the blocks in a sprint start.

3. Third class lever – the effort is in the middle between the fulcrum and the load.

The effort is in the middle of the fulcrum and the load, as exemplified during a biceps curl.Third class lever

During a biceps curl, the fulcrum is the elbow joint, the effort comes from the biceps contracting and the resistance is the weight of the forearm and any weight that it may be holding.

To recall the order of the levers use the term 'FLE' - this will help you to remember which part of the lever is in the middle.

First class lever - Fulcrum is in the middle.

Second class lever - Load is in the middle.

Third class lever - Effort is in the middle.