Flexibility Part 1: Nervous System and Mobility

I've been on a bit of a flexibility kick lately, so I've decided to put some time into covering a few aspects that could be helpful to those of you who pursue an active lifestyle. Flexibility is simply the normal extensibility of all soft tissues that allow the full range of motion of a joint, and it really is one of the most widely misunderstood concepts of fitness. For decades we've been told to stretch before activity, but we're finding that the way you stretch will determine whether or not you actually do prevent yourself from injury. I'll go more into that later though, first of all, I want to cover the physical nuts and bolts of flexibility, as in, what makes an otherwise healthy joint unable to complete a full range of motion?

First let's look at the Nervous System (NS)

The NS is made up of billions of cells that come together to form a communication network of nerves within the body. Without a nervous system, we wouldn't be able to interact in any way with our surroundings. Think of it like that Metallica song where the guy is in the hospital paralyzed, with no arms or legs, blind, deaf, and unable to speak. That's kind of what it would be like without an operational NS. It is literally our command center and it serves a few main functions within the body.

Let's set up a scenario to illustrate the three functions in action. Of course, I'll use gung fu because our sensitivity training really captures the essence of NS function. Let's say we are blind folded going through a flow drill in which we must punch forward and deal with whatever interruption there may be. Without being able to see, we are relying completely on our sense of touch to tell us what's going on. This is called the Sensory function and it relays messages from what's called afferent neurons (basically sensory neurons that transmit nerve impulses to the brain or spinal cord). So when we throw the punch but come into contact with the opponents hand blocking our strike, our afferent neurons tell us where the block is coming from, the force in which it's being applied and the direction. The impulse is sent to our Central Nervous System (CNS: the brain/spinal cord) where the second function is initiated. The Integrative Function is the translation of the initial afferent nerve impulse, this is where our CNS turns the input into output, it decides what the best course of action is in relation to the specific sensory impulse and relays that message back to the muscles via the third and final function: Motor Function. So let's say the block is coming from the outside and pushing with a lot of force towards the inside. Your CNS would get the signal and interpret it into the correct counter that you've trained into your muscles, which would be to collapse at the elbow, biu jie, lop sao with a qua choi, palm phon sao, chung choi. The Motor function would relay this signal through efferent neurons (motor neurons) which transmit from the brain to the muscle and initiate the action.

This is why we teach you to be loose and to startle in class, because this reflexive form of training is so fast and explosive when you get out of your own way. Think about when you pick up a hot pan and immediately drop it. You don't think about how to open your hand and pull away, you just do it. When you train the gung fu movements sufficiently, they become instantaneous reaction, not thought out processes. But I regress, back to the NS.

What you really want to take from this, is that all movement is directly controlled by the NS, showing that it's empirical to train the NS efficiently to ensure proper development of movement patterns.

Now, you may be wondering if the NS and the CNS are the same thing, and the answer to that is no. The CNS combines with the Peripheral Nervous System (PNS) to create the whole NS. We already know that the CNS is the brain/spinal cord, which means the PNS is what branches off of the CNS. It includes 31 pairs of spinal nerves, 12 cranial nerves, and sensory receptors. The PNS has two functions that we are going to look at. Firstly, they connect the command center (CNS) to the different effector sites such as muscles and glands. Secondly they send info from the effector sites back to the brain through the use of sensory receptors.

Sensory receptors are structures that specialize in transforming different environmental stimuli into sensory information for the CNS to interpret and respond to. Some are for detecting light, some are for pain, others are for chemical reactions such as taste or smell. The ones I want to focus on for flexibility purposes are Mechanoreceptors which only detect distortion within tissues. They are located within muscles, tendons, ligaments, and joint capsules and they detect all forms of distortion such as compression, traction, tension, or stretch. They each play a different part and each serves a function to defend against injury to the joints or muscle.

We are going to look at the Muscle spindle first because these are structures that are sensitive to change of length and rate of length change within a muscle. They run parallel to the fibers and when the muscle stretches, they do too. They monitor the change in length and when the muscle stretches too far or too fast, they get excited and cause the muscle to contract, ensuring that the muscle is not injured.

Secondly is the golgi tendon organ. This is located at the spot where the tendon meets the muscle and they do the opposite of the muscle spindle. They monitor the amount of tension within a muscle when it's being contracted. When excited, the GTO will force the muscle to relax so that it will not be under excessive stress.

Lastly, there are the joint receptors that are inside and around the joint capsule. These guys look out for pressure, acceleration, and deceleration of the joint. When you get put in a deep arm bar, these are what tells the brain to tap out or change position.

These mechanoreceptors are our bodies main line of defense against muscle strains and tears, they act as a reflexive guard that makes us drop those dumbbells when we can't do another press, or stop a foot from the ground when we are trying to do the splits. They decide how far and how much our muscles, tendons, and ligaments can go or do and their range of motion can be interfered with by a number of things. We can, however use these to our benefit when it comes to increasing flexibility.

There are several different training methods for flexibility and each one has it's own time and place to be implemented. Let me be clear that flexibility isn't all about doing splits and back hand springs. When you hear someone be referred to as "flexible" you usually imagine that they can do some sort of non-functional trick like putting their feet behind their heads or fitting themselves through a tennis racket. That's not what I am talking about when I train people to increase their flexibility. I'm much more concerned with ensuring that you have the capability to put any and all joints through their full range of motion so that you learn to move and be active without the threat of injury.

Be aware that stiff muscles, or imbalanced muscles (i.e. tight quadriceps, weak hamstrings) makes maintaining proper posture very difficult to do. When you have postural imbalances, it usually causes you to have improper, altered movement patterns which results in, at the very least, a heightened chance of injury coupled with the inability to move or function to your full potential. These movement compensations or postural distortion patterns, stem from a lack of structural integrity that stem from a decreased functioning of components within the kinetic chain (the combined muscular, skeletal, nervous system). When you have poor flexibility within any one of your muscles, you can develop what's called relative flexibility, which is a compensation where the kinetic chain (KC) seeks the path of least resistance while performing a movement.

Take, for instance, the squat. A lot of people out there do this crazy sort of sumo squat where their toes are pointing outward at an angle. When they lower into the movement, their knees follow their toes and they are able to get all the way down into the bottom of the squat. This presents some problems though because when you turn your legs out like that, it makes the knees open up in a way that can allow for ACL tears, it fails to activate your hip adductors,  and it can lead to other postural imbalances further up in the chain such as in the lumbar/thoracic spine. The feet should always be pointing straight forward, regardless of how wide your hips are, and if you're unable to squat without turning out the feet, it means that somewhere you have a limited range of flexibility and your body is altering it's functional movement pattern to adjust for that weakness. Maybe you have tight calves which prohibits ankle dorsiflexion, if so, you would have to work on loosening up your calves. Perhaps you have trouble internally rotating your hips, in which case you would need to spend time increasing the range of motion in that plane.

It's important to remember that your body is one organism. A lot of folks think of their shoulder and hip as being two different entities, but they are parts of the same body. Think of it this way... if you lack external rotation in the shoulder joint, so whenever you do anything above your head in the gym, you have to put a lot of extension into your lower back to get the arms to go straight up. This over extension causes the pelvis to rotate forward (already affecting the hips), the rotated pelvis lengthens the glutes and hamstrings, putting them in a stretched position, which tightens the calves and shin musculature. Understanding this, you can see how important it is to develop flexibility in all joints so that it becomes possible to move in the proper postural structure.

Before I finish up here, I want to cover different ways muscle imbalances specifically effect movement. A few terms you will need to know are agonist and antagonist. A muscle that is contracting to perform a movement (say a bicep contracting to curl a dumbbell) is an agonist. The antagonist would be the muscle that performs the opposite motion (the triceps). Every agonist has an antagonist, and their relationship should be one of balance. When the balance is lost, and an agonist becomes tight, the neural drive of the antagonist becomes decreased. This is called altered reciprocal inhibition and it can result in some problematic movement dysfunctions such as synergistic dominance (SD).

SD is your body's way of working around a weak or inhibited prime mover. A prime mover is the big muscle associated with a movement. If you bench, your prime movers are the pecs. Pull ups would be the lats and so on. When the muscle is weak or lacks mobility due to tightness and poor flexibility, the responsibility goes to the synergistic muscles that usually only help to stabilize and support the prime mover. These muscles are nowhere near as efficient at performing the movement on their own and are unable to guide the movement naturally. A great example is having a tight psoas (hip flexor). When the psoas is tight, the glutes are weakened because of reciprocal inhibition that was mentioned above. The weakened glutes can't perform hip extension as well now so when a person squats, they have to rely on the synergists which are the hamstrings, adductor magnus, and erector spinae for compensation. This in turn alters the angle and forces applied at the joint. This alteration is called arthrokinetic dysfunction and it very often leads to injury.

Let's look at the outward turned feet again in the squat. When you alter your movement because of restricted mobility, the joints are at a weakened position. Your entire movement chain is now altered and muscles that should be in a lengthened position, such as the gluteus maximus, are tightened and compacted, so force output is greatly depleted and movement is limited. In order to compensate, the hamstrings become synergistically dominant, stressing the knees and lower back (which can lead to more compensations further on), leading to pain and eventually injury.

With all this in mind, it is easy to see how important basic maintenance is when it comes to range of motion and flexibility. There's a lot more at stake than just not being able to do the splits or kick high, you can effectively injure any number of body parts due to a tight muscle that may or may not be located in another part of the body.

The next few parts will cover how we go about loosening up these joints and muscles so that we can improve posture and improve movement capability. I look forward to reading any and all comments you may have regarding your personal experiences with muscular tightness and movement restriction.