The interaction between bone and muscle during arm or leg movement is called lever. The force used to move the bone is called the fulcrum. Muscles exert tension or force during skeletal movement. The point of the lever where the force is applied is called the effort arm and the point where the force is attenuated is called the resistance arm.
The components of the lever are four.
1. Rods or bars
2. Falcrum or Pivot – Rods act on it
3. Load or object – It moves against the force
4. Ball – It provides the force in the movement of the rods.
Classification of Lever
Livers are divided into three categories.
1. First class lever: The lever which has the falcrum between the load and the ball is called the first class lever. The 1st vertebra of the spine joins with the human crown to form the first class liver. Due to this lever, the head can be rotated forward, backward, up and down.
2. Second class lever: The lever where the weight is between the falcrum and the ball is called second class lever. Class 2 levers are formed when the heel is raised by resting on the toes. Because of this lever one can run fast.
3. Third class lever: The lever where the ball is between the falcrum and the load is called the third class lever. 3rd class lever is formed when an object is lifted by hand. Due to this lever, more weight can be lifted with less force.