Every lever has a point at which force (or power) is applied, a point of resistance and a fulcrum (or axis), but the three different types of levers, all of which play a role in sport and physical activity, work slightly differently.
• First-class levers have the fulcrum between the force and the resistance. An example of a first-class lever in action is a person stands on tip-toe : the length of the foot is the arm of the lever, the ball of the foot acts as the fulcrum, and the Achilles tendon and calf muscle provide the force, lifting the weight of the body by the back of the heel.
• Third-class levers have the force between the resistance and the fulcrum. Our forearms act as third-class levers, with the rower’s oar the force is applied by the rower, the fulcrum is the oarlock, and the water offers the resistance.
• Second-class levers have the resistance between the force and the fulcrum. An example of a second-class lever is when a elbow as the fulcrum of point of rotation of the lever.
Most of the levers are used in sport, however, are third-class levers. These levers are better at generating speed than force because of the position of the fulcrum. Lengthening a third-class lever increases the speed that can be achieved. The additional length increases the range of motion of the lever’s end and, therefore, its speed. This in turn results in more force at the end of the lever. For example, using a bat or request adds length to the forearm, which acts as a lever, and allows a ball to be hit with more force.
The principle of leverage states that the velocity at the end of a long lever is faster than the velocity at the end of a short lever, and that the end of a lever will move more quickly than any other point on the lever.
The first two types of levers enable heavier weights to be moved with less force using mechanical advantage.