The Anatomy of A Muscle

Do you know how many muscles make up your body?

If your guess falls between 650 and 840, you’re correct! The number of skeletal muscles in the human body is within this range, depending on how you count them up. When you stop to think about how each of these work on a different hinge to keep us moving, it’s an amazing system that rivals those constructed by even the most advanced architects.

A skeletal muscle is a muscle that helps you to move. It interacts with a given joint in your body and pulls on the hinge to extend, or contract, a limb. Ultimately, your body is a giant pulley system where the muscles control the amount of pressure pulling on either side of the pulley to control how open or closed any given hinge or joint is.

While going into extreme detail about how every muscle fibers works would take dozens of blog posts, let’s get a bird’s eye view of the system you’re using each and every time you exercise or go about your daily routine!

After all, it’s always more enjoyable to practice something when you understand how that something works — plus, a basic understanding of your muscles can help you maintain their overall strength and health!

What Makes It Move?

Every muscle in your body is a meshwork tapestry of two different types of muscle strands. These two types of fibers are Myosin and Actin. Together, these two types of muscle filaments make up a myofibril — that is, a functioning contractile unit in a muscle. The myofibril is the part that does the “pulling” illustrated in the earlier example of the pulley/hinge dynamic that extends or contracts each joint.

Myosin filaments are made up of hundreds of golf club shaped bits that are attached to one another. Actin filaments are strung together in a similar way. The myosin filaments are sometimes referred to as “thick” muscle filaments, in contrast to the thinner actin filaments.

Did you know there is one myosin filament for every actin filament? They grow in pairs and depend on one another. If you fold your hands together, your fingers interlocked, you can see how actin and myosin filaments connect as a whole myofibril — just like the side-by-side strands in a crocheted hat. If you pull your hands apart but keep your fingers interlocked, you can see how the filaments sit with one another while your body is at rest.

This difference between the filaments being at rest and contracted demonstrates how and why your muscles “flex,” or look bigger, when they are actively engaged. The microscopic fibers are literally stacking on top of one another to pull the opposing ends closer together.

This also explains the relationship between muscle mass and strength. If you have more muscle fibers, there is more volume being stacked up, providing defined muscle tone. On the strength, having more fibers pulling produces more force.

Your muscles contract, or pull together, when the right chemical signals are distributed to the muscles, on command, from your nervous system.

As you can see, there’s a lot going on behind the scenes whenever you’re moving, and especially when you’re exercising! This explanation just skims the surface. So anytime you complete an activity — whether it’s a boot camp session or even folding the laundry — take a moment to stand in awe of this complex and fascinating system!