Moved to: Should you shorten your stride?
Which brings us to “stability”. Stability is touted as a virtue in all domains (especially financial) and is emphasized in nearly all sports. It is touted as a means to better posture. But I think a simple exploration of how the parts of the body interact explodes the myth of better posture or functioning through stability.
All parts of the body function together. There is no way to isolate one part of the body from another. If you raise your arm, every major joint in your body must adapt to support the change in balance. If any articulation is stabilized, then this work of adjustment becomes more difficult. So the notion that there is a right position for the head, for the arms, for the hands is wrong. Maintaining any part in a position makes global adaptation necessary to support all action more difficult. In running, the proper functioning of the bi-articular muscle system requires that no joint is “stabilized”. In order that all leg muscles retain the same length throughout leg extension requires that no joint is stabilized.
The myth of core stability is an example of one faulty notion. There are no “core” muscles. The entire system works as a whole, and it is completely artificial to imagine that some muscles are “core” and others are not. Further, the idea that you can willfully activate (contract!) certain muscles to the benefit of overall functioning needs correction. For example, if you contract and hold any muscle, that muscle becomes less adaptable. Certain large muscles, like the rectus abdominus (abdominal muscles) must constantly change length and tone in all actions. Holding them just interferes with them.
If one perceives that some muscles are not doing their work, if they are weak – again, the abdominals are a good example – then the solution is rarely to strengthen them. It is to discover why they are not working, as they would if they are receiving the pulls of adjoining muscles. In the case of the abdominals, they go slack when the hip joints are over stabilized. If the hips are freed, the abdominals will take up their proper tone. This is very easily demonstrated.
What happens in running? Well, the forces that generate locomotion operate perfectly in most toddlers. They see something or someone they want, and they extend their bodies towards that thing or person. The weight of the head is released slightly forwards, taking the extension of the body against gravity into a forwards vector. This is not a fall, because, as the body’s weight moves more forwards on the foot, a reflex is stimulated which extends the legs. The body extends in space at an angle. The degree of angle will determine the extent of extension, and thus, the speed of movement. When the body is this extended off of one leg, the other leg is free to fall forwards, pulled their by the passive stretch imposed on the psoas during extension. The leg will come forwards and land on the ground before the body’s weight falls, so there will be no “landing” on the leg, instead, the extending body will come over the foot, until the weight reaches the forefoot, again stimulating the interosseus reflexes which make the leg extend.
Some notions of running mechanics seem to suggest that maintaining certain positions is necessary for good running form: positioning the head over the shoulders, keeping the shoulders over the hips, making a light fist with the hand, maintain a 90 angle at the elbows, etc. Nothing could be further from the truth, as variables like speed and incline alter, so must the entire postural system. We can compare the muscular system to a three-dimensional spider web, in which all fibers are interconnected, such that lengthening or shortening any fiber will affect all other fibers. Every movement made by the body involves the entire muscular system, and, because all movement changes balance, the importance of freedom of the skull upon the spine cannot be overestimated.
Our standing posture gives us many advantages in the animal world. Our ability to run is perhaps the most outstanding of these advantages. The extension of the human body against gravity in standing is very quickly adapted to movement. A slight release of the head’s weight in the intended direction to movement allows us to use our entire system of extensor musculature in a manner that leads to efficient movement.
Let’s analyze our verticality. As stated above, the weight of the head is poised atop the spine, prevented from falling forward by muscles at the rear of the neck. The pull of gravity on the toppling weight of the head stimulates a stretch response in neck and back muscles, giving them the tone they use to extend the spine against gravity, and to maintain the spine in conditions propitious for supporting the ribcage and the internal organs against the pull of gravity.
The head’s condition is constantly altered in response to sensory input. The inner ear canals send information to the brain about linear and angular acceleration. The brain takes these signals, along with input from the eyes about our relative position in the seen world, and input from sensors on the skin — cutaneous sensors, in the muscles and joints (muscle spindles and golgi receptors) — and uses them to make constant adjustments to muscle tone to balance us and to prepare conditions for possible movement. For any possible movement, we can first map a change in the poise of the head, which prepares the spinal musculature to support the movement of a limb to move a finger. This pathway of movement, through the hierarchy of postural reflexes beginning with how the head is poised atop the spine, recapitulates the path of fetal development of movement. There is an organizing of the whole system off of which specific muscular action is constructed. This is posture – the conditions of the whole being are used to prepare for actions in relation to the perceived world, and the whole being adapts in action to changes in the planned course of action based on constant input during action.
A simple way to describe the function of a vertebrate might be: “Get the mouth parts to the food”. The primary reason for the development of self-motored movement is to acquire food (well, that and sex). There are organisms which root in food, there are those that float in a medium which occasionally delivers food, and there are those which have evolved motors allowing them to seek out food. All vertebrates have evolved around a spinal column with brain, eyes, ears and mouth at the leading end. When snakes move, it is the head that leads. Quadrupeds and bipeds also lead with the head in basic walking and running patterns. For example, when a lion smells or hears prey, it will orient its head in the direction of the prey to see it. (tonic neck reflexes) The substantial weight of its head is then oriented in the direction of possible movement. If the lion decides to move towards its prey, a release of the weight of the head in the intended direction begins the extension of the spine, which then allows the extension of the limbs. The animal puts itself off balance in the direction of intended movement to create an extension of the whole body towards an objective. This is easily seen in running quadrupeds – the spine lengthens in the direction of movement – the faster a horse wants to run, the more its head will be moved forwards from the body.
In bipeds, such as humans, extensor reflexes create our vertical state, working against (and with) the pull of gravity. Our neutral upright condition is not, as is often claimed, created by stacking one element on top of another as in bricklaying. If we were truly evolved in this way, with the head centered on the spine, with the spine centered over the hip joints, knee joint, ankle joints, then movement would require contraction to displace something to initiate motion. In fact, there are wonderful imbalances in our structures that allow for quick movement with a simple release of existing muscle tone. See The Spinal Engine
Actually, one doesn’t have to have any detailed anatomical knowledge to see that the body is not, should not, be aligned in any sense of the word. Although the human body is fairly symmetrical laterally, it is certainly not so in depth – if it were, you’d have a butt in front to balance your butt (you’d have a front rear-end). You would have a foot which extends behind your heel, and you would have muscles equivalent to your calves in front of your shins.
Starting at the top, it is obvious that the head does not balance on top of the spine like a ball on a stick. The center of gravity of the skull is well forwards of the atlanto-occipital joint at the top of the spine. Note the origin of muscles, even those which attach to the sternum and collarbone, is at the rear of the skull. In a standing human, the pull of gravity on the skull stimulates action in muscles posterior to the skull, helping to extend the spine. In a well organized body, posterior muscles support the weight of the organs which are in front of the spine. Large muscles, including the gluteus muscles, prevent the trunk from falling forwards from the hip joints, in much the same manner as posterior neck muscles prevent the head from falling forwards. We see the same thing at the lower leg – in healthy standing, weight is not centered under the ankle, but is well forward on the foot, making the calf muscles work constantly to support standing.
Through this inherent instability, the muscular system integrates. Through it, we not only sense where we are in relation to gravity, but the muscular action necessary for proprioception is stimulated. Remember, the only way that you can sense where your limbs are in relation to each other is through constant change in muscle length. You don’t feel where your arms are in space – your body calculates the degree of change in muscles and knows where you are because of movement. (This is the same with all senses, in fact, which require movement for their functioning. Try feeling texture without moving your hand. If an image does not move upon the retina of the eye, we cannot make sense of it.)