For a lever, the ratio of the perpendicular distance of the line of action of the effort from the fulcrum, to the perpendicular distance of the line of action of the resistance or load from the fulcrum. That is, mechanical advantage = force arm/resistance arm. When the mechanical advantage ratio is less than one, a force that is larger than the resistance must be applied to cause motion of the lever. Most skeletal levers appear to be relatively ineffective because they are third-class levers with a mechanical advantage of less than one, but this low mechanical advantage means that a small movement of the lever at the point of force application moves the load through a relatively large range of motion.
Subjects: Sports and Exercise Medicine.