 Hi, everybody. We're here today to talk about basically skeletal muscle biomechanics. In the last lecture, we talked about the mechanism of myofiber contraction. We talked about sarcomeres, myosin, actin, and the actual molecular interactions that are taking place within muscle cells themselves, skeletal muscle cells. In this lecture, we're going to take a little bit of, we're going to back up a little bit and look at a few concepts of how muscle organs act overall, and just some interesting characteristics of muscle function. There's actually a lot of research happening in this area because muscle biomechanics are important for exercise and competition. So there's lots of people who want to maximize their performance. And so understanding the biomechanics of how your muscles actually work can play a role in that. So the first thing we're going to look at is why muscle cells, why do we get tired? Why do our muscles get tired? And what is that? It is fatigue when you think about a skeletal muscle organ.