Imagine you've just completed a tough upper-body workout. Your muscles feel a bit tired, but all in all you're able to go about the rest of your day just fine.

The next morning, you wake up and realize the back of your shoulder blade feels stiff. When you rub your shoulder muscles, it feels like you're prodding a little gumball under your skin. Every time you try to move it around, the area feels tight, with slight pangs of pain.

Over the course of the next few days, your back slowly loosens up and eventually your shoulder returns to feeling normal. It's probably something you'd like to avoid or minimize in the future if possible, though. So what was going on with that muscle knot?

I'm an exercise physiologist. The goal of much of my research is to understand how different movements and forms of exercise place stress on the muscles. Figuring out programs to maximize performance, regardless of training goal, goes beyond what to do during the workout—it's also about how best to prepare for and recover from the stress exercise places on the body.

Some of the most common questions I've heard during my years as a personal trainer and researcher in this field involve muscle knots. What are they and how can you get rid of them when they happen?

What are muscle knots?

The knots you detect in your muscle, which may feel as small as a marble or even as large as a golf ball, are called myofascial trigger points. The fascia is the thin layer of connective tissue that surrounds the muscle.

When your muscle gets damaged—even just a little—it can cause inflammation in the bands of muscle and the fascial layer above. And that clump of inflamed tissue is a myofascial trigger point. The little lumps are typically tender to the touch and can limit your range of motion or lead to pain during various movements. Muscle knots don't show up on medical imaging scans, and researchers are still trying to figure out the exact physiological mechanisms within the muscle that cause this reaction.