Gray Cook likens the brain to putting on the handbrake, tightening a muscle to prevent further movement in a particular direction when the brain perceives part of the body to be in danger, or when it perceives that it doesn't have full control or is about to lose it. And so when a muscle is tight it doesn't necessarily mean that it needs to be stretched. Instead what needs to be looked at is why the brain is turning that muscle on.
When looking at other bodies as a therapist, the tendency may be to focus on motor control. However, an equally important quality for yogi's and anyone else interested in improving body awareness is sensation, particularly the sensation that indicates the condition of muscles (relaxed, active, stretched) and connective tissue (relaxed or stretched).
This may or may not be monitored by the somatosensory cortex (the counterpart to the motor control cortex). However, it's easier just to say that the brain contains the necessary circuitry to turn muscles on and off and the circuitry (or programs) necessary to process and interpret information that comes from the bodies sensors.
We can hijack or ride on the backs of both systems consciously. And the better we understand the body, the more experience we have of it, the better we can get at consciously overriding those systems or at least making conscious tweaks to it.
And the reason for doing this isn't so that we have to do it all the time, but to give our body better habits in the first place. We become our own therapist or teacher or instructor, at least in regards to operating our body more effectively in any given context.
(In this case habits could be likened to muscle memory, actions that we can do without thinking, but can at the same time monitor and make adjustments to).
This isn't to say that we'll be free of teachers, but rather, learning from someone else, the learning is then limited to choreography. Because we already know the body the teacher isn't labored with the task of teaching us how to feel and use our body and how to learn the choreography or movements or poses or whatever they are teaching us whether yoga, tai ji, playing an instrument, operating equipment, using hand tools, assembling or dissasembling.
The key quality that is important for both motor control and sensitivity is tension. An additional quality is pressure. Both qualities can be callbrated to varying degrees and both can be used to both control the body and feel it for better mind-body coordination.
Tension can be important for motor control because with the right amount of tension (not too much and not too little) the body can be easier to control with minimal effort. And for sensing the body, the right amount of tension gives us a "feel" for our body.
A very simple and basic way to create "basic" tension is to create space or length. As an example expanding the ribcage, and drawing the head away from the ribcage and the ribcage away from the pevis can add tension to the waist, intercostal tissues and neck giving both feel, some stability and control of the torso. Making the arms and legs feel "long" is a basic means of adding tension to hips and shoulders.
Looking at other people it's generally easier to use alignment points teach and check that students are doing poses or actions correctly. Practicing feeling our own body and teaching students to feel theirs, with something as simple as feeling muscles relax and contract, gives them the tools to become better at figuring out the best alignment from the inside.
In addition, instead of having to think about how to align their bodies, they can focus on feeling their body, and experiencing it. And as their experience grows they can get better at fine tuning their positioning and movement.
With a better understanding of the body (and better experience and better motor control and sensitivity) it then becomes possible to work towards operating the body with greater effectiveness, speed and smoothness in more and more activities. Starting with limited external change (akin to learning to drive in an empty parking lot) this control and awareness can gradually be applied to handling external change as well as internal change (driving on local roads, driving on highways, racing.)
In this respect sensitivity is applied to noticing both the body and the environment outside of the body (the internal environment and the external environment) and then controlling the body in such a way to respond effectively to what is sensed in such a way that the overall goal is still achievable.
To learn motor control and sensitivity (the two go hand in hand) progress gradually. Start with unweighted move towards weighted, start with isolated move towards integrated.
If there is difficulty with feeling and controlling a body part even in isolation we can look at other parts of the body to see what may be causing the difficulty.
It reminds me a bit of working with circuits.
Relays are turned on an off by turning its control circuit on or off. But a relay can be latched on so that even when its control circuit is not running current it is still on. The ability for a relay to turn on or off may be affected by other relays in the circuit. The better we understand the circuit as a whole or the better we are at fault finding the easier it is to find out why a particular relay is stuck in the on or off position. We can then fix the problem to regain correct functioning. Depending on circuit complexity, solving one problem may only reveal another problem, or the inability to solve one problem may have at its heart another problem.
Looking at the system as a whole, and whether it functions as desired, the relays and their circuits are the things that we can look at to see why the system isn't working. How do we find the problem, by turning things on and off, by measuring, and seeing what works as it should and what doesn't.
While it can be possible to decouple elements of the body so that they can be practiced and learned in isolation, as we reach extremes, the maximum stretch of a muscle, or the end limits of a joints movement range, it becomes more difficult to keep the part thoroughly isolated and so tension or lack of tension in other parts of the body can affect the part in question.
And so where possible, conscious muscle control is best learned well within the comfort zone of the part in question.
With even a little experience the focus can then be on maintaining control closer to the limits of movement.
Working at the limits we may find that the brain has turned a muscle on to maximum to prevent further movement. This is often the case when stretching (or trying to stretch).
What do we do? We could stay and wait for the body to relax or realize it's safe, or we can play with activating other muscles till we find the activation that allows the problem muscle to relax.
This assumes that the goal is a relaxed stretch, where the intent is to keep the muscle being stretched in a relaxed state. Other options for stretching include activating the opposing muscle, or activating the muscle being stretched while at the same time causing it by lengthen by using gravity or opposing muscles. Another technique is to activate the muscle and move out of the stretch and then relax it while moving deeper into the stretch.
By trying out different muscle activations we help the brain recognize what to do in the new position. The necessary muscles activate in turn causing other hindering muscles to relax and this allows us to move deeper into the stretch until the brain turns on the brakes again.
We can repeat the process within a session or realize at a certain point that we have reached a muscles maximum stretch for that time. So time to rest.
A question could be, how does the brain recognize problem situations? How does it know when to turn muscles on to act as brakes to prevent further movement? Does it recognize that we are doing the splits and that they are "dangerous" or is there something else happening some signal within the body that it recognizes and responds to.
I'd suggest that it too looks for excess in tension or pressure. There's some limit at which it applies the brake before the limit is passed. But rather than just looking at muscle tension or lack there of, it also looks at joint capsule tension or pressure or both.
At this point it would be helpful to introduce a man by the name of Jaap van der Wal, MD, PhD who suggests that something called a muscle dynament be the fundamental architectural unit that includes muscle belly, tendon and ligament. In this model muscle tension not only affects tendon tension, it affects ligament tension also. And this in turn affects joint capsule tension.
In this case it could help to liken a Joint capsule to a water balloon. Squeeze it in the middle and the end points move away from each other. Muscle tension could affects the joint capsule envelope in much the same way, directly adding tension to the ligaments so that tension around the joint capsulte is balanced and so that pressure within the joint capsule prevents bone ends from pressing against each other.
Why is this quality, for bones to be able to adjust at their joints, important? So that tension can be freely trasmitted through out the body. In tension integrated systems (tensegrities) compression elements or spaces, which is what bones are, do not directly connect. While their general relationship is maintained by tension elements they can move relative to each other so that external tension can be dispersed throughout the tension network of the system.
With the human body this doesn't always happen automatically because we have the ability to control and vary the shape of our body and the amount of tension in any part at any time. However, I'd suggest that if the goal is a movement of pose where the whole body is active and involved with minimal wasted effort, then tensegrity could be the quality of the body in this end state.
Going back to how the brain senses a problem, if a muscle isn't activating as required this can affect joint capsule envelope tension. An imbalance in tension within the envelope caused by an injury or a muscle not activating as required could cause the brain to compensate by activating another muscle to either act as a brake or to add the required tension to the joint capsule or both.
Note this is my theory and I've tried it out with respect to overcoming knee pain and using this understanding has helped.
But even if joint capsule tension is okay, a muscle may fail to activate (perhaps it is latched of because another muscle is active) and so the brain turns on other muscles to substitute. As opposed to maintaining ideal joint capsule tension this may simply be muscles supporting the weight of the body or limb and because they are compensating the feeling is off pain, or tightness because the muscle in question is working close to it's limit, or it may be overworked, doing its regular job and substituting for the muscle that is seemingly on holiday (but is actually locked out of the house without any means of informing any one of what has happened.)
A muscle may not "fire" because the brain doesn't recognize that is is available or because it is prevented from firing by other muscles that are active.
In such situtations it helps to understand that muscle tension not only creates sensation, but it also affects relationships between bones. In cases where muscles are compensating for other muscles, in movement or stillness, bone posiitoning or aligment will be affected.
When working on motor control for larger muscles it is generally easy to directly feel the muscle in question activating or relaxing. With smaller, thinner or less densely grouped muscles it can be more challenging to feel muscle activity directly. Instead we can rely on sensing the results of their actions, tension in connective tissue that results as the connection points of said connective tissue move away from each other.
For example, to feel the position of the ribcage relative to the pelvis, the tissues of the waist can offer the necessary sensory feedback.
I should point out here that as an engineer and technician there was a need to calibrate tools and instruments. This was so that we could count on our measurements and changes to be accurate. The body is no less different. After learning to interpret signals from our body we can then callibrate them so that we can with increasing accuracty feel the relative position of the parts of the body.
Bones can be felt indirectly via tension in connective tissue. We can thus sense alignment and if it is imbalanced we can experiment with correcting aligment, this may cause some msucles to relax and others to activate and it may unlatch other muscles allowing them to activate as desired.
Now all very well and good for me to say that I can do this and I beleive in this, how is this useful for people who wish to improve body awareness or who wish to teach it?
Perhaps one of the most important qualities to aim for when introducing or teaching body awareness is slow and smooth movement. This forces deeper awareness of the body. And it allows the mind to wander within the body giving it time to notice tension pressure and or a lack of it.
Corrective measures can then be taken.
Generally I want my students to understand the movement first, and in initially it can be a little rough. But once they have the basic movement then I like to have them work at doing it slow and smooth.
Another technique for better motor control and body awareness is to practice repeated isolated movements with the targeted body part decoupled.
This means being as relaxed as possible and making the movement as easy as possible but while giving the targeted muscles a firm foundation from which to act.
As an example when doing shoulder blade isolation movements I generally suggest a lifted and open ribcage.
If multiple movements and instructions are being used I suggest a maximum instruction set such that the instructions can easily be acted on without having to think about them. Generally this means working within the limits of short term memory. Note that in this case I'm talking about repeated movements. Repeated movements make it easy to learn the motor control for the body part in question. With these repeated movements the idea is to pick an instruction set that isn't too big so that the student can easily hold that instruction set in short term memory. They can then follow the instructions without having to think.
How do you know if you've exceeded the limits? If you or your students constantly have to figure out what it is that they have to do, even in a repeated movement. If you or your students have to think about what to do then shorten the instruction set.
Generally after enough repetition, and it often doesn't take much, a movement might be learned to the point that instructions can be built on.
This is pretty much the same technique I use when learning Chinese characters. I'll paint a few strokes repeatedly till they are in mid term memory, then I'll practice another set of brush strokes or add a few more brush strokes to those I've already learned. In each case the idea is to only practice a quantity of brush strokes that I can easily remember.
Note that if boredom is evident even with a focus on feeling the parts that are moving, then it may be time to up the challenge. This can be done by making the movement more harder (from non-weight bearign to weight bearing) or adding complexity (re-integrating the movement) so that more of the whole body is involved.
Note that tightness or weakness may be signs that something isn't working. The trick is to get it to work, I'd suggest looking at alignment first, wiggling or rotating to find the right groove recognizeable by a muscle turning on with the right amount of tension or an overly tight muscle relaxing to a comfortable level. This can be true when working well within what could be considered "normal limits". It can also occur when you are trying to push back your limits. In this case, rather than forcing a stretch I'd suggest the intelligent approach would be to play with motor control. Try activating different muscles related to the muscle in question till you hit the right activation.
Note that a key both in doing or teaching isolated or integrated movements is knowing what you are doing. Actually this applies the level of motor control and body awareness also. When we know what we are doing we can direct our awareness and motor control effort effectively for sensational yoga poses and sensational experiences in general.
Going back to the basics, a very simple idea that you can practice in any pose is create space or length. However another important idea is that of creating stability. Know or choose which part of your pose is your base, generally the part closest to the earth, and with that part stable focus on lengthening upwards and outwards from that stable foundation.
For more advanced practitioners the goal can be to keep a pose relatively still while at the same time finding a balance between space and relaxation. For beginners the goal can be to move between these two extremes, lengthening and creating space and then relaxing, and repeatedly moving between these two extremes to get a feel for (and improve control of) the body. With enough of this experience it can then be easier to work towards a static pose with a balance between the two qualities.