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.