So I left off a while back having discussed the MAIN STRUCTURAL COMPONENTS responsible for flexibility (bones, ligaments, etc.) to give some idea of the hard limits that we have to our total joint range. But as most of us realize, that’s not the whole picture. After all, it’s not usually our skeleton that’s restricting us in day-to-day activities.
Where do we typically feel “tight” instead? In our muscles! And that brings me to the major focus of this blog entry — the NEUROMUSCULAR SYSTEM!!!
You see, the primary job (mechanically speaking) that our muscles have is, simply put, managing joints. Put another way, they’re primarily responsible for making sure that the bones can actually maintain proper contact with each other, can move (or not move) properly, and that force can be distributed throughout our bodies in an appropriate way. If our muscles are working well, then we’re having a good time. If not, then we start to see dysfunction — in the form of pain, arthritis, weakness, poor performance, coordination issues, and all sorts of other not-so-fun stuff.
So to illustrate how some of this works, we have to break down the actual structure of a muscle and the “stuff” it interacts with. Note that this will be PRETTY basic, but there’s still some science ahead. So saddle up!
Muscles are, at least in my opinion, some of the coolest things ever devised by nature. They consist of tons of tightly packed subcellular machinery that allows our bodies to convert the chemical energy of our food and the products of food breakdown into actual mechanical energy (FORCE)! This is no small feat. I won’t get into the metabolic pathways and mechanisms that govern this right now, but just know that there’s a lot of stuff that has to happen for your muscles to work! So let’s talk a little about their structure (feel free to skip this portion if you’re already familiar with basic muscle structure):
— BEGINNING OF SCIENCE!!! —
***Keep in mind that this post is going to talk about skeletal muscle. This is the stuff that attaches to our bones and helps us move. There are two other types of muscle — cardiac (heart muscle) and smooth (which operates in our organs and around blood vessels) — but this isn’t immediately relevant to us. So I’ll stick to skeletal muscle today.***
First off, I want you to look at the structure of a typical muscle. Notice that it’s a big hunk of tissue that’s attached to a bone by something called a TENDON. But when we break it down, we see that the whole muscle is actually comprised of a bunch of chunks of muscle units called “fascicles.” The word “fasciculus” actually means “bundle” in Latin. This makes perfect sense, as you can see that each fascicle is really a bundle of individual muscle fibers. I sometimes like to think of it as a bundle of straws wrapped in a thin sheet of tissue. And all of those bundles come together to make the whole muscle. Also– in muscles, a “fiber” is the same thing as a “cell.” So keep that in mind if you see it anywhere else. Again, FIBER = CELL.
This gives a good basic overview of how our muscles are organized on a larger scale. Now let’s look a little closer at a single muscle cell (one of the straws) to see how it’s put together:
So we see that, even on a smaller scale, things are bundled up in a similar fashion. Inside a single cell, we see these individual cylinders called “myofibrils” that have their own components within THEM. It is within these myofibrils that the smallest functional unit of a muscle is found — THE SARCOMERE. I won’t get too deep into how this little guy works, but suffice it to say, these are where the magic really happens. Here’s one last picture to help you visualize things on this microscopic level:
So all you really need to know about sarcomeres is this — tiny little proteins (filaments or myofilaments) inside the sarcomere attach and “crawl” over each other so that each end (the Z-disc or Z-line) is pulled toward the middle. Now all of these sarcomeres are attached end-to-end (in “series” as it is known). If we zoom back out a bit, we can imagine how the whole muscle will shorten as each individual subunit shortens. Here’s a neat way to visualize this:
Imagine you and nine friends are all side-by-side, and you each represent a single sarcomere. You each have your arms outstretched and are holding hands with the person next to you. Now imagine that, while doing this, you’re sitting on a REALLY slick surface so you can pull all of the people on either side of you closer to your position. If you pull your arms in (“contract” like a sarcomere), you get “thinner” and the people on either side of you will slide in towards you. The overall length of the system (all 10 people) will get a LITTLE BIT shorter. Now imagine if ALL TEN of you do the same thing. Every person pulls the people they’re holding hands with closer to them. As you might imagine, the whole chain will get MUCH shorter, as everyone is pulling their arms in at the same time. This is what happens within a myofibril, and within a whole muscle on a larger scale. The whole muscle shortens, because TONS OF INDIVIDUAL SARCOMERES SHORTEN.
I mentioned earlier that muscles generally attach to our bones at what is called a tendon. While they don’t generate force directly, healthy tendons are absolutely vital for allowing us to transmit that force from our muscles to the bones (or vice-versa) and do all of the things that we ask our bodies to do. If a tendon fails, then the muscle can’t do its job. This is important to keep in mind, as these structures are often overlooked when we talk about building strength and power and developing our physiques. We’ll look at tendons and how they are involved in stretching a little more later.
— END OF SCIENCE!!! —
So from all of this, we can see that there’s an intricate structure that contributes to the way our muscles do their jobs. Millions of tiny units work together to create the large-scale movements that we see and use every day.
I needed to go into the structure of muscles a bit so you have a basic understanding of the pieces that make up the whole. Muscles are an intricate (and WAY COOL) system of components that come together beautifully to allow us to perform all of the actions of daily living that we take for granted. Without muscles, there is no controlled movement. So now that you know a little bit more about how muscles are put together, what about the effects of stretching? How does attempting to move into extreme ranges affect these tissues? I’ll describe this in the next entry 🙂