What does it mean if a lever is at a mechanical disadvantage?

The mechanical advantage of a lever is the ratio of the load to the effort. If the effort is bigger than the load, it is sometimes called the mechanical disadvantage.

In a first class lever the fulcrum is between the effort and the load. Usually the fulcrum is closer to the load such as with a crowbar. In this case the effort is smaller than the load and you have a mechanical advantage.

In a second class lever the load is between the effort and the fulcrum. An example of this would be a wheelbarrow. For this case the effort is always further away from the fulcrum and you have a mechanical advantage.

In a third class lever the effort is between the load and the fulcrum. In this case the effort is always closer to the fulcrum. The effort is always larger than the load and you have a mechanical disadvantage. Examples of a third class lever are your forearm, a snow shovel, a baseball bat and a golf club. In each of these cases the effort is larger than the load.

With a snow shovel you have to lift with more than the weight of the snow. In your forearm the elbow is the fulcrum and the muscles have to lift with more than the weight of the object in your hand, because the muscles are attached so close to the elbow.

You might be wondering why we use third class levers, since they have a mechanical disadvantage. We use them because the load travels a greater distance than the effort, so we gain speed. We can throw the snow because it goes faster. (But don't try doing that with heavy, wet snow. It leads to pulled muscles and heart attacks.) With a baseball bat we hit the ball harder with greater bat speed. Same with a golf club. We gain speed. Golfers can hit the ball 340 yds. with great club speed.