This tells me that the origins for 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 that. And it shows us one of those muscles, the hamstring, that's the biceps for Morris. All right. So to figure out the lever system, I wanna look at this muscle and the biceps for Morris has its origin upon the issue tuberosity. It also has an origin on the back of the femur there. But that's not gonna change anything about this problem. And it has an insertion on the proximal end of the tibia and the fibula right there. Now, to figure out my lever system, I need to find the fulcrum, the effort and the load. So let's start with the fulcrum, the fulcrum, we said is the pivot point. So the pivot point for this movement, it's gonna be the knee. So I'm just gonna put a point there and put an f, that's my fulcrum. All right. Next, let's think about the load. Where is the weight that this is moving? Well, the weight is in the leg, it's, you know, somewhere out here is gonna be the center of gravity of the leg, something like that. So this is gonna be my load. So then the question is, where's the effort? Well, we said you find the effort by finding the insertion or the muscle that's doing the movement. So my insertions right here. So I'm gonna put effort sort of right there at that proximal end of the tibia and the fibula. So as I look at this and now I try to remember what lever system is this. I can remember my mnemonic device, the Eiffel Tower had an Elf but he fell and I look what does this spell out? It spells out left. That wasn't one of my options. But if I read it the other way it spells out fell. The Eiffel Tower had an elf but he fell. This is a third class lover system. In a third class lever system. The effort is between the fulcrum and the load. So does a third class lever work at a mechanical advantage or disadvantage? Remember, a mechanical advantage means the lever makes it. So there's less effort needed to move the load. Mechanical disadvantage means that you have to put in more effort to move the load. So what does a third class lover do? Third class lover works at a disadvantage? So we said that the whatever is closer to the fulcrum tells you your advantage or disadvantage here, the effort is closer to the fulcrum. So that means it's gonna be take a lot of effort to move this load. So why is this muscle arranged this way to make it take more effort? Well, remember the benefit of third class lovers is that the end of this rod here where the load is, is gonna move really fast and have a large range of motion. So if you wanna run fast, you want your legs to have third class levers in them. And this is why so many of the muscles of the arms and the legs work as third class lovers.
3
Problem
Problem
In what type of lever is the force applied between the fulcrum and the load?
A
First-class.
B
Third-class.
C
Second-class.
D
Force cannot be applied between the fulcrum and the load.
4
Problem
Problem
The majority of the lever systems in the arms and legs are third-class levers; there are few second-class levers. Knowing this which of the following statements is correct?
A
The muscles of the arms and legs usually work at a mechanical disadvantage.
B
These joints will have relatively small range of motion.
C
Most movements of the arms and legs prioritize power over speed.
D
The fulcrum will most often be placed between the effort and the load.