 You might think a muscle cell is a muscle cell is a muscle cell, doggie, and guess what? It is not so. Not all muscle cells are equal. Not all myofibers are equal. So I'm reminding you again of our structure. Here is a bundle, a fascicle is a bundle of different kinds of myofibers, different muscle cells. I'm about to tell you that, well, I already told you that not all muscle cells are equal. Some of them are different than others. So consider the muscle fibers in this young laddie, Dennis Cameto, from Kenya, ah, get out of there, goodbye. What was that? What was that, and why did it show up? Didn't want me talking about old boy Dennis Cameto. Who is the Kenyan Marathon world record holder? And he ran the marathon in like two hours and two minutes or something like shocking. And remember, a marathon is 26.2 miles. Okay, this is the body that can run a marathon in two hours. Now look at that body and compare it to this guy who ran, holds the record for the 100 meters. 100 meters is, I can run 100 meters. I cannot run a marathon. And he, if this guy tried to go out and run a marathon, it'd be a sad story. And if this guy went in and tried to run the 100 meters, it would also be a sad story. And the question is like, why, what's the scoop? Here's the deal. If you imagine, this is the picture that I'm showing you, this is actually a cross section of a muscle organ. These are fascicles, and they're separated by perimysium. And they're little, but each little circle is an actual muscle fiber. So it's just a cross section of a bunch of different myofibers, and what do you notice about them? Well, we've got bright ones, light ones, and we've got dark ones. And the fact is that you have the, that's the truth. You have different kinds of myofibers, and they're quick twitch and slow twitch. Quick, that says quick, twitch, and slow twitch. And I want to make sure you understand that what we're talking about here is very, very general and superficial because I'm explaining quick twitch and slow twitch muscle fibers in like one minute. And there's a huge amount of variability here. There's a lot of research that's happening. Quick twitch fibers are lighter in color than slow twitch fibers, which are darker. Slow twitch fibers are full of mitochondria, and they, what's the role of a mitochondrion? It goes through cellular respiration. And if it's going through aerobic cellular respiration, that means there's oxygen at the end of the electron transport chain, which means we're making a lot of energy. Quick twitch muscles go through, that was an interesting look, and then aerobic respiration, which means they don't make nearly as much energy from the glucose. They tire quicker, but they twitch faster. The contraction is faster and more explosive. Most of us can go, oh yeah, my legs are made mostly of quick twitch fibers. That's just the truth. I sort of wish they were made of slow twitch fibers, and I enjoyed running because I think exercise would be a lot easier, but I'm definitely a quick twitch human. You could do a muscle like biopsy and find out. I could do that on my small human who isn't going to be a muscle man, but I could find out, dude, am I going to try and make him into a sprinter or a marathoner? I have my guess about which body type he is more likely to have, but you could actually do an analysis and figure that out. Hmm, that seems a little crazy talk, but you know, we could do it. Okay, yeah, that's good enough. Are you happy? I'm totally happy. Okay, now, the same muscle can do fine things and big things. The same muscle can pick up a heavy rock and a light Rubik's cube. And how, how does that happen? How can we pick up different sized things? Let's go find out.