How foam rolling works

Confession. I used to think that muscles were like play dough. I believed that if you rolled and tugged on them, they would change shape and flatten out.

Okay, I didn’t think this exactly, but I did have a very simplistic view of how the body worked. In my head, mechanical input in equaled mechanical input out. I figured that if you pulled on a muscle it would get longer, if you contracted a muscle, it would get shorter and if you rolled on a muscle, you were changing its shape by making it flatter, softer or longer. 

Then I learned a bunch of complicated sh*t about the nervous system and realized my model of how foam rolling works had some big flaws. I also discovered that a lot fitness professionals and clients were armed with the same misinformation that I was.

As I’ve stated, our muscles and surrounding tissues are not inert substances that can be molded like clay. They don’t passively give into the forces exerted against them. Rather, they are largely and somewhat unconsciously governed by the nervous system.

If we aren’t changing muscle length when we foam roll, why do many of us experience improved mobility?

Humans are complicated. All of the muscles we know from gross anatomy (e.g. muscles we can see like biceps and triceps) are made up of bundles of muscle fibers that are enveloped by lots of layers of connective tissue (fascia). Embedded in the fascia and muscles are lots and lots of mechanoreceptors.

We are still learning what all of these mechanoreceptors are and what they do, but for our purposes today, they are sensory organs that respond to mechanical stimulus like touch or pressure that set off neural feedback loops to adjust the tensional and positional relationships between our muscles and joints.

We used to think that these feedback loops went all the way back to the brain, but there is new evidence showing that many of them don’t even travel that far. This tells us how much of this is beyond our conscious control.

When we foam roll or stretch and we experience a feeling of release or lengthening, it’s due to how we’ve stimulated the mechanoreceptors in the muscle and the fascia. It is not because we’ve permanently deformed or changed the length of the muscle and its surrounding tissues.

When we stretch or apply pressure to a muscle, we excite several mechanoreceptors, including one called the golgi tendon organ (GTO). The GTO is located near the tendons and monitors tension in the muscle.

If we stretch to tolerance (think slow and gentle), the GTO will send a signal to the nervous system to tell the muscle to relax or “lengthen.” The GTO can’t tell the difference between a sustained, gentle stretch or a slowly induced compressional force, so if we foam roll a muscle using slow, moderate pressure, it should have the same response.

However, if we move too far or fast into a stretch or we aggressively compress the muscle with too hard of a tool, then it will send a signal to the muscle spindle, another sensory structure, to contract the muscle in an effort to protect the joint.

This is one reason why you want to take your time when stretching or foam rolling. If the stretch or pressure is too hard, too fast or too deep, you will actually create more guarding and tension in your muscles, not less.

This is only part of the story though. Foam rolling (and stretching for that matter) affects more than the muscles. It also targets the fascial or connective tissue system.

As I previously mentioned, fascia is the stuff enveloping and giving organization to our muscles. It is a fluid-based system that runs from our skin to our bones. It houses our sensory nervous system and it has a large role in supporting, protecting and stabilizing our joints.

Like muscle, fascia also has specialized receptors and contractile properties and if it is well hydrated, it helps our body maintain appropriate tensional relationships between the muscles and joint spaces.

Well hydrated fascia can be equated with ease of movement. All of our tissues glide appropriately over one another. Muscles fire in good timing and hold with appropriate length and tone, so we have minimal joint compression. However, should our fascia become dehydrated from long bouts of inactivity (think sitting) or repetitive motion (yes exercise can do it too), we may experience some negative side effects.

When fascia becomes dehydrated, the cells will lose space and become stuck together, not unlike scar tissue. This can cause movement to feel stiff. The muscles enveloped in the dehydrated fascia may feel “tight” and have delayed firing patterns. The nerves entrapped in the affected tissues can become irritated with the end result being increased tension, joint compression and pain.

*Update since I originally wrote this post: There’s now some evidence that these changes are more about the stimulation of the nervous system + increased and less about fascial rehydration. However, I’ve found the practical application to continue to be beneficial.

What can we do to rehydrate the fascia and restore some of the sensory information that is lost from too much sitting?

For starters, we can move more frequently in varied ranges of motion. We can also manipulate the tissue to stimulate the connective tissue cells to pull in more fluid. There are a few ways to do this, but the main ones are gently lengthening the tissue and short bouts of moderate compression.

Enter foam rolling.

As I mentioned above, when we foam roll, we light up the mechanoreceptors in the muscle. However, you can’t work on muscle without having a conversation with all of the nerves and connective tissue surrounding it.

So while you “roll out” your muscle, a bunch of things are also happening in the fascia. If you create compression slowly and pause to create tugging on the tissue (e.g. movement of your body against the roller), then you are stimulating the connective tissue cells to pull more fluid into the cell walls and to create more space and organization among themselves.

It’s thought that this is one reason why people often have less stiffness after using a foam roller or getting a massage.

Additionally, like muscle, fascia has contractile properties and its own set of receptors and these receptors also respond to various amounts of stretch, speed and force. This is still in the research phase, but there is evidence suggesting that a certain amount of “bounce” or speed can actually allow fascia to “let go.” Before you go ballistic stretching, there is a caveat to this.

Too much speed or force, be it from an aggressive workout or using too hard or blunt of a tool to foam roll your muscles can damage the fascia and rip apart individual muscle fibers, creating scar tissue formation, decreased mobility, impaired power and poor muscle timing.

And on that note, should foam rolling hurt?

I’m often asked, “If it doesn’t hurt, how do I know that anything is happening?”

I think we place way too much value on inflicting pain on ourselves, but here are a few of my thoughts on compression techniques (foam rolling, massage, ect) and pain.

Compromised tissue and muscles with high tonicity are going to be more sensitive when you push on them. This is because sensory nerves tend to be more irritated in restricted tissues.

So if you find one of those areas, you have some information. You know that this may be an area worth working on, but you also know that you need to be gentle. A little hurt so good is okay, but remember everything I just said about the fascia and the mechanoreceptors. If you go too hard, too fast or too “novel” in your approach, your nervous system will brace those structures in order to protect you from yourself.

Additionally, some areas anatomically have less muscle and more nerve outlets (think close to the bones), so it’s going to hurt more to push on them. If you find one of those areas, stop pushing so hard and if you’re pretty sure you are hitting more bone than soft tissue, get off it. You aren’t going to “release” anything.

What about the areas that aren’t sensation worthy? Should we use a harder tool? Is anything even happening?

It’s still valuable to work on them. Sometimes, when an area has become overly restricted or inhibited, we lose sensation there. Gentle to moderate compression can help remind our body that it exists.

On the flip side, it might just be that you are on healthy tissue and making a few passes for maintenance certainly isn’t a bad idea, since you’re still stimulating the fascia and the mechanoreceptors.

And on the note of using a harder tool, it depends on what you mean. If you’ve been using a softer roller for a long time and you want to try something with more direct pressure, sure play with a firmer roller. However, don’t go taking blunt objects like barbells and mashing them into your muscles for the sake of sensation. You’ll only create problems for yourself by damaging your soft tissues.

That was more blah-blah-big-words-science than I intended. Here are the practical take aways that you can apply to foam rolling (aka a summary).

  • When you foam roll, you are having a conversation with your tissues and your nervous system. You are not rolling your muscles out like play dough. Remember, you cannot permanently deform tissue. That IT Band is not getting any longer. 😉
  • Go slow and gently increase application of pressure. When you find a tolerable pressure (no gritting of teeth) pause or apply a shear force by creating motion of the structure over the roller.
  • Sensation is a poor measure of progress. If you are too aggressive, you will actually create more damage to the tissue and bracing in the muscle, not less.
  • Take all of this with a grain of salt. LIke most of fitness, the science of foam rolling isn’t really science (yet). It’s scientific theory applied to massage that has been reapplied to foam rolling. However, we do know that it can help decrease pain sensations and it is generally accepted that it improves mobility.
  • Use common sense and enjoy the benefits. There are many!

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