Category: Applied Functional Science
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True story: I [Doug] was a child once. Now that I am an older child, I have many fond memories of growing up. My father, Gary Gray, too, has fond memories of me (and my older brother, Brad) growing up.

One such story involves Brad and me playing outside while our father performed an item on his “honey-do list,” in the garage. Prior to him getting to the list, he told us kiddos to play in the backyard. Translation: Do NOT play in the front yard. Suffice to say, Brad and I ended up playing in the front yard. This warranted our father to come out to the front yard, to calmly remind us of what he told us (“Please play in the backyard”), and to kindly return playing in the backyard.

Guess what happened next … Brad and I returned to the front yard! Why? Because our dog, Astria (a striking female German Shepherd), dropped off her #2s in the backyard. Makes sense, right? In fact, when our father came back out to the front yard, he asked us why we ended up there again, even after he definitively told us to stay in the backyard. It was then that my brother shared with him the answer above – Astria poops in the backyard and we didn’t want to step in it. Yes, makes sense indeed.

Let’s ask ourselves a fundamental question about the above scenario. Why did our father want us to play in the backyard? The answer is that it appears safer than the front yard, which is closest to the road, where cars are, where children shouldn’t play. Is the front yard really dangerous, though? No. In fact, it creates an environment of more fun (especially when you don’t have to step in #2s).

Training (and Prevention and Rehabilitation) is not very different when it comes to backyard versus front yard scenarios. Let’s call the backyard “traditional mindsets.” Let’s call the front yard “functional mindsets.” For example, a traditional mindset when it comes to the knee is that it needs to stay over the foot within movement. A functional mindset would say that the knee better not stay over the foot because that is not what it does when it does what it does. Granted, the knee over the foot appears to be the safest place for the knee to be to not get injured. The knee, however, is able to not only bend and extend but also go in, go out, rotate in, rotate out – which is what it does when it does what it does! Therefore, if the knee moves in all three planes of motion, yet our training, prevention, and rehabilitation does not facilitate the knee moving in all three planes of motion, then this backyard approach is really not the safest, nor best / ideal, strategy.

A functional mindset goes on to emphasize the importance of tweaking movements from safety (also known as successful) in manners that are safe (also known as small, subtle changes) to enhance the safety (also known as expanding the threshold of movement) to not only recreate the biomechanics of the task, but to ultimately create a “Buffer Zone” within the task for even more safety.

To go deeper into this approach, it helps to bring in the all-important proprioceptors. Specifically, we want to take a look at the Golgi-Mazzoni Corpuscles, which are one of the proprioceptors that reside in articular tissues. Golgi-Mazzoni Corpuscles have been found primarily in the joint capsules, but also are present in the cartilaginous labrums. In spite of our relative lack of knowledge about the Golgi-Mazzoni Corpuscles, research about the location in the joint capsule, as well as the type of mechanical force that stimulates them to fire, can provide insight. The greatest density of Golgi-Mazzoni Corpuscles is found at the margins of the capsule where the attachment to the bone occurs. The Golgi-Mazzoni Corpuscles do not respond to tension like most other proprioceptors. Instead, they produce sensory information when they are compressed from inside the capsule. That compression force is perpendicular to the direction of the capsule.

Knowing what stimulates them, combined with the location in the capsule, begins to provide insight regarding the information they provide. When a joint moves in a certain direction, a portion of the capsule gets taut and is pulled down against the bone. As the inner surface of the capsule contacts the bone, the Golgi-Mazzoni Corpuscles will be compressed and “fire.” The Golgi-Mazzoni Corpuscles on the taut side indicate that the joint is near the end of the range of motion.

Two additional features of Golgi-Mazzoni Corpuscles are important to consider. First, they have a relatively high threshold of compression before they fire. Second, they are very slow adapting to this compression (meaning, they will continue to fire as long as they are compressed). There is some evidence that the higher the compression, the more frequently they discharge.

So it appears that Golgi-Mazzoni Corpuscles are critical to safety, preventing motion beyond the anatomical limits of the joint. This would infer that training and rehabilitation programs must include (rather than avoid) movements that work joints near / at the end of range. Instead, then, of keeping the knee over the middle of the foot (not functional), movements must purposely promote a functional amount of valgus. Allowing all joints to work near the end of range is not a threat to safety if the movements are based on success and properly tweaked. When this occurs, the information from the Golgi-Mazzoni Corpuscles can be integrated (subconsciously by the body) with other perceptual information to actually promote safety and reduce injuries.

So what, who cares, why is this information so important? Gray Institute® has coined many phrases, including the following statement: “Movement turns on proprioceptors, proprioceptors turn on muscles, and muscles control the movement.” The proper (functional) movement is key, which is why 3DMAPS® (3D Movement Analysis & Performance System) is so vital to any assessment and any progression / program.

The practical application of our limited knowledge of Golgi-Mazzoni Corpuscles comes into play with ALL of the movements in 3DMAPS®. To better demonstrate this, let’s take a quick peek at the Performance System Movement called “Elevated (Lunge Leg).” The tweak of the six Analysis Chain Reaction® Movements starts by positioning the lunging leg on an elevated surface. This initial starting position brings multiple joints of the stationary leg close to end range. Using the pelvis (for more of a “mobility” tweak / focus) or bilateral hands (for more of a “stability” tweak / focus) to drive movement in all three planes, the global movements create joint motions that will cause the Golgi-Mazzoni Corpuscles to “fire.” The additional propropceptive information enhances the neuro-perceptual picture of the body, which is subconsciously used to orchestrate human movement. (Learn more at https://www.grayinstitute.com/courses/maps.)

There are two functional situations that make it is essential to create (through movement and / or pre-positioning) individual joint motions near the end of range. Both were described above. First, there is the functional authenticity of joint motion exemplified by the knee valgus position. If the knee goes there during function, then our training and rehabilitation programs must successfully take the joint there as part of a global movement. Second, there is the strategy of taking a movement, and the component joint motions of that movement, into positions that are beyond those normally encountered during a sport or activity to create a “buffer zone.”

If the body never experiences these movements during our training programs, but they occur either frequently (as part of normal function) or infrequently (as part of an occasional exaggerated movement), then the seeds of failure and injury have been sown. Imagine being the “supervisor” of the command center for movement and suddenly you receive information from the Golgi-Mazonni Corpuscles from multiple joints. What does this information mean? Is there danger? Should the movement continue or be aborted for the sake of safety? The unexpected information creates chaos. The well-intended strategy of limiting motion now becomes the reason that injuries occur during function.

Keeping the role of the proprioceptors in mind, both the Analysis and Performance Movements of 3DMAPS® can be modified to fit the needs of each individual so that our programs enhance, rather than inhibit, function. Long story short, our patients / clients can play freely – and safely – in the front yard!

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Proprioceptors Series Part 3 – Golgi – Mazzoni Corpuscles – Part 1 Vlog

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