This tells me that the origins of the three hamstring muscles are on the ischial tuberosity. The insertions are on the proximal end of the tibia and the fibula. And it says, knowing this, what type of lever system is the hamstring a part of when it performs the movement of flexing the knee? Then it wants to know, would you expect the hamstring to work at a mechanical advantage or disadvantage when it performs this movement? And to guide us a little bit, it has an image of somebody flexing their knee, bending their knee backwards like this, and it shows one of those muscles of the hamstring, the biceps femoris. So, to figure out the lever system, I want to look at this muscle. The biceps femoris has its origin on the ischial tuberosity. It also has an origin on the back of the femur there, but this is not relevant to the problem. It has an insertion on the proximal end of the tibia and the fibula right there.

Now, to determine the lever system, I need to identify the fulcrum, the effort, and the load. First, the fulcrum is the pivot point, which for this movement is the knee. So let's represent the knee as the fulcrum. Next, the load is the weight being moved, which is largely the leg itself. For our diagram, we can assume the center of gravity of the leg represents the load. Finally, the effort comes from the spot where the muscle attaches and exerts force, which in this case is the insertion on the proximal end of the tibia and fibula.

Recalling our mnemonic device: "The Eiffel Tower had an elf, but he fell," it spells out 'left' when arranged in one way, but not relevant to our options. Reading it the other way, it spells out 'fell,' indicating a third-class lever system. In a third-class lever system, the effort is between the fulcrum and the load. This means that the hamstring works at a mechanical disadvantage because the effort is closer to the fulcrum, necessitating more effort to move the load. Despite this disadvantage, the third-class lever arrangement allows the end of the leg to move rapidly and with a large range of motion, which is advantageous for running. This is why many muscles in the arms and legs operate as third-class levers.