The biceps muscle provides the effort (force) and bends the forearm against the weight of the forearm and any weight that the hand might be holding. The load is further away from the pivot than the effort. There is no mechanical advantage because the effort is greater than the load.
When you try to curl the weight, your bicep has to work harder because it is at a mechanical disadvantage. The elbow joint as a third class lever.
third class lever
The biceps attach between the fulcrum (the elbow joint) and the load, meaning a biceps curl uses a third class lever.
Learn more about biceps here:
