 All right, hamstring group. The hamstring group is found in the posterior compartment of your thigh, and there are a couple of things that make this group a group, a couple of ways that we can think about them or sort them to help us organize. First of all, almost all of them, 75% of them, attach to the ischial tuberosity. And the ischial tuberosity, remember, is the bone you sit on. So when you, like, sit on somebody's lap and dig your ischial tuberosity into their thigh, into their quadriceps group, that is going to make them very sad, and you probably won't be sitting on their lap for very long. Now, I said that almost all of these, this group attaches to the ischial tuberosity, and in fact, all except the short head of biceps. So semi-membranosis and semi-tendinosis, both also attached to the ischial tuberosity. So you're probably wondering, dude, what's the scoop with the short head of biceps femoris, and that attaches just, it smears on the femur, smears on femur. And then let me tell you the action of these muscles, and then you can tell me what you can figure out from the second attachment. The major action for all of these guys, they all flex the leg. They all flex the leg, which means where do they need to attach? They, no matter what, they have to attach to the tibia or the fibula somewhere on the leg. So let's break it down, break it down, and figure out where everybody attaches distally. The biceps group, all of them, attached to the head of the fibula, all of them. So both these guys, attached to the head of the fibula. Now think about that. From ischial tuberosity, which is pelvis, or from femur to the head of the fibula, that will definitely enable us to flex the leg. Semi-membranosis and semi-tendinosis, those guys attach to the tibia, and they both attach medially to the tibia. Medial tibia. And in fact, semi-membranosis is slightly more medial than semi-tendinosis, but there are other ways that we can tell. If you flex your leg, not your thigh, if you flex your leg, you can feel on the lateral side of your leg, you can feel a tendon, and it's only one tendon. It's the shared tendon between... Did I say lateral side already? It's the shared tendon with the biceps femoris group, the long head and the short head, both attached to the head of the fibula, and you can feel that tendon on your posterior leg, thigh, when you flex your leg. If you go medial and palpate the same basic location on the medial side of your thigh, and get your fingers in there, and you can actually feel two tendons, and that is semi-membranosis and semi-tendinosis, and they're attaching to the medial side of the tibia, and you can feel both of them. Because most of these guys attach to the tibial tuberosity, what is their other action? You know that since they spanned the knee joint, they have to do something to the knee, and they actually, oops, I already did that one. You know since they span the hip joint, they have to do something to the thigh. And you tell me, what are they going to do? They're on the posterior aspect, they're attached to the tibial tuberosity, they're going to extend the thigh. Do you think the short head of bicep femoris is going to extend the thigh? No, doggies, it doesn't even cross the thigh joint, hip joint, so it can't. But semi-membranosis, semi-tendinosis, you know they're extending the thigh. That's not a thing where you have to lie on your belly and you do leg curls, thigh curls, that's working your hamstrings group. Let's go take a look at these guys. Look, who's this attached to the femur, to the head of the fibula? That would be biceps femoris short head. Let's look at biceps femoris long head. Same attachment, keep your eyes on this attachment, ready, go. Look at that, there's the long head. Long head is attaching to ischial tuberosity, just like we noticed. How about semi-membranosis? We're expecting semi-membranosis to attach to the medial side over here and also to ischial tuberosity, so see if you can see that happen, ready, go. Oh, nice. Now, semi-membranosis has this weird, I'm sorry, it looks like a membrane-y tendon to me. And so if I'm looking in a posterior thigh of a human, I can find semi-membranosis quite easily because it has this really unique look. Same location, perhaps a little bit more lateral, we're going to see semi-tendinosis. Are you ready, get set, go. There it is, now look at this. The tendon on semi-tendinosis is holy crikey's long. And so it actually makes it pretty easy to recognize it in a body. That's it. Now let's do our lateral rotators, of which there is one.