Mechanical advantage of levers
Some levers operate with mechanical advantage. This means that the lever can overcome a large load with relatively little effort. Mechanical advantage is very useful for joints which are weight bearing as they have to overcome the weight of the whole body.
Mechanical advantage can be expressed as:
Mechanical advantage = effort arm 梅 resistance arm
Therefore, the greater the effort arm in comparison to the resistance arm, the greater the mechanical advantage.
In the three lever examples on the previous page, the second class lever provides the most mechanical advantage and this explains why it is so crucial that it operates at the weight bearing foot.
At take-off, the high jumper applies large forces to the ground through their ankle. The ankle operates with mechanical advantage in order to resist these forces and enable the jumper to achieve flight