I [Doug] thoroughly enjoy music. I like to have music playing as much as possible. (Confession: I am listening to music right now as I type portions of this blog.) Music evokes a response – perhaps energetic, exciting, relaxing, dramatic, depressing, numbing, romantic, [you fill in the blank].
Therefore, music evokes a response, as mentioned above. Movement, too, evokes a response, as to turn on proprioceptors.
When it comes to music, I respect all forms, even though I might not prefer (or even like) all forms. Personally, I am a hip-hop, country, and R&B fanatic – quite the combination, I know.
Since I am talking about music, I would like to briefly discuss the orchestra. Dictionary.com defines orchestra as “a group of performers on various musical instruments, including especially stringed instruments of the viol class, clarinets and flutes, cornets and trombones, drums, and cymbals, for playing music, as symphonies, operas, popular music, or other compositions.” I was not aware that the orchestra was all-encompassing, which is pretty doggone cool. While this intrigues me, something else within the orchestra does as well – the conductor.
The conductor is the glue to the musical production. Michael Bowles, in “The Art of Conducting,” states the conductor’s job description as the following:
- Interpret score of composer in manner reflective of specific indications within score;
- Set tempo to score;
- Ensure correct entries by ensemble to score; and
- “Shape” phrasing of score where appropriate.
Essentially, the conductor receives the score, studies the score, responds to the score, preps the ensemble on the score, delivers the score, and is able to influence the score where appropriate.
Therefore, the conductor influences the orchestra for the output of the production. In a similar fashion, Muscle Spindles (proprioceptors) influence the muscles for the output of the task.
Muscle Spindles have a unique status among all of the proprioceptors. By virtue of their location within the muscles and the existence of a contractile (motor) section within the spindle, these sensory receptors have great influence on the muscle synergies created by the body to execute a task. The questions become:
- Why is there a section of the intrafusal fiber that can contract (lengthen and shorten)?
- How would this influence the neuro-perceptual information from the spindle and, ultimately, the synergies created during human movements?
Within the spindle, there are fibers. These fibers are referred to as intrafusal because these are within the fusiform encapsulated receptor and in contrast to the extrafusal muscle fibers that actually create muscle force. The sensory endings wrap around the intrafusal fibers. Since the intrafusal fibers connect directly or indirectly to the extrafusal fibers, they lengthen as the muscle lengthens resulting in discharge of two different types of sensory nerve endings. It is accepted that Muscles Spindles provide information about muscle lengthening and the velocity of that lengthening. Recent research in animals, as well as to a limited extent in humans, has supported these assumptions while providing more insight into the exact nature of the information.
It is the unique contractile ends of one type of intrafusal fibers that is most interesting. The spindle functions like a strain gauge. The more it is stretched the more it fires. When the muscle is in a shortened position, the gauge would be lax and fire very little, if at all. When a muscle is in a lengthened position the gauge would be stretched to a great degree and firing at a great rate. But, then again, questions become:
- What if the body desires more consistent information from the muscle spindles?
- What if the information desired needs to be relatively the same whether the muscle is short or long?
For years, Gray Institute® has suggested that the contractile section could function to influence the sensitivity (“gain”) of the muscle spindle as it “measures” changes in length and velocity. If the muscle were in a stretched position, the spindle “gain” would be turned up. But if the contractile ends could relax, then the spindle sensitivity could be more constant. Likewise, if the spindle sensitivity was decreased by a shortened position of the muscle, then the contractile ends could tighten, again keeping the “gain” about the same. The benefits of a consistent sensitivity of the “spindle gauge” is that the sensory information would be less influenced by muscle length, and more indicative of length change and velocity no matter what the length of the muscle was.
Recent research has started to give insight into when sensory information is produced by the muscle spindles. Because the motions in the human studies are passive and isolated to a single joint, caution must be exercised when trying to interpret these findings. There does appear to be a residual “gain” (or sensitivity) of the Muscle Spindles at rest. The contractile elements at the ends of the intrafusal fibers may set this “gain.” This “gain” appears to be influenced by recent movement history. This would suggest it is critical to create movements that take joints to different locations in the available range of motion at different speeds. Sympathetic nerve endings have been identified in the spindles. This suggests that the “gain” is influenced by our state of alertness and other behavioral drivers such as pain. There is so much more that needs to be discovered about muscle spindles, which begs one fundamental and important question:
- How should what we are learning influence our training and rehabilitation programs?
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.
Global movements, such as the Analysis Movements of 3DMAPS®, can be used to “train the gain.” Tweaks to the Analysis Movements are the basis of the Performance System in 3DMAPS®. Any “train the gain” strategies will always be consistent with the Principles of Applied Functional Science®, particularly including all three planes of motion, as well as using the authentic drivers of different body segments. Proprioceptors desired authenticity in all aspects of movement, which is why 3D is vital. Muscles do not lengthen and shorten in one plane but in all three planes.
Besides using speed to train the Muscle Spindles, there are two aspects to training muscles at different lengths. The first aspect is the beginning position of the body. This determines the length of the muscles at the start of the movement. The second aspect is excursion of the movement. Another way to describe (or ask) this is as follows:
- How much movement occurs from the starting point until the position when the motion is reversed (in the Transformational Zone)?
From the muscles’ perspective, this means how much length change occurs before the movement is decelerated. Both aspects – starting position and movement excursion – contribute to “movement history” experienced by the Muscle Spindles throughout the entire body.
As we “train the gain” functionally, the goal is to create a diverse “movement history” in order to increase the chances of success in a variety of conditions and positions. All of the movement strategies in the Performance System of 3DMAPS® will contribute greatly to this. Exceptionally powerful is the Performance Movement dubbed as “Support,” where both hands and both feet provide enhanced stability (by leveraging a doorway, wall, or even TRUE Stretch). With both hands and feet providing stability, the individual’s body moves easily through larger excursions (generating more mobility throughout the body). Tweaking the position of the hands and feet will alter the starting position so that length changes produced by the excursion begin from a different starting position (muscle length). With movement in different planes, at different speeds, using different body segments as drivers, from different positions, and varying the excursion, a rich “movement history’ experience can be created for each individual based on their needs, wants, and goals! (learn more at https://www.grayinstitute.com/courses/maps).