Tires, Slides, and Golf Balls
Have you ever convinced someone an object you were about to toss them was super heavy when in reality it weighed next to nothing? If you haven’t, I suggest you (safely) give it a try. You’ll see them move in a radically different manner than had they realized the object was so light. This is because of how our our musculoskeletal-systems works. To understand this, we’ll need to talk about joints, like your shoulder. We’ll also need to talk about how muscles, like those that compose your rotator cuff, function. Finally, we’ll take a step back and look at how the musculoskeletal-system works. For this blog, we’ll start by discussing joints.
In most of your joints, bones both roll and slide on each other to produce movement. First, lets talk about rolling. Picture a tire rolling down the street. As the tire rolls, no part of the road or tire stays in contact with the other. Now think of a kid on a slide. The kiddo’s backside (or belly) stays in contact with the slide, but moves from one part of the slide to the other.
Now, let’s put the two together. Imagine (or place) a golf ball on a tee. Slide the golf ball and it falls off the tee. Roll the golf ball and it rolls off the tee. Now, roll the ball one direction while sliding it in the opposite direction. If done in the correct proportion (think dimmer-switch coordination), the ball stays on the tee.
This is how joints, like your shoulder, work. The round (convex) part rolls one direction and slides the other on the other bone in the joint. And, this motion is largely controlled and coordinated by our muscles. So, now that we know how most of our bones move on each other at joints, it is time to discuss how muscles function in next week’s blog titled “Dimmer. Not Flip.”
