In a yoga class, one is often directed to keep a “long” spine. Teachers will even say that being able to lengthen the spine helps the cerebrospinal fluid to flow more easily. Well, let’s explain why that is not true and how that kind of false belief can even be potentially harmful.
First, let’s us really understand what CSF is. Cerebrospinal fluid is a fluid that circulates throughout the spinal canal and across the surfaces of the brain, which at any given moment is about 150 ml (in the subarachnoid space) in volume. The entire volume of CSF is replaced about every 8 hours and everyday about 500 ml in total is produced. The contents of this fluid consists of mostly proteinaceous material (proteins) and a concentration of certain simple ions (the distributions of these materials can change depending on which areas of the spine CSF is inhabiting). Its function is to facilitate shock absorption of the brain and spinal cord from mechanical shock. (So if you fall or bump your head the fluid is there to minimize the impact on your brain and spinal cord, yay!), keep the hydrostatic pressure of blood vessels in the brain in a safe zone to prevent aneurysms when changing your relationship with gravity (so wait, inversions don’t increase blood flow to the brain? whaaaaaa? Well, it’s a bit more complicated than that, but suffice it to say that no, inversions do not increase blood flow to the brain.) and maintains a constant environment for various brain cells by transferring metabolites in and out of the deeper recesses of the central nervous system.
So we can all agree, based on the information above, that an unobstructed flow of CSF is necessary for optimal health. No argument there. So then wouldn’t it be natural to assume that humans have evolved (or were created, if you prefer) to structurally inhabit the movement of CSF in a way that most benefits us without having to consciously create an internal environment for that function. Why would we assume that? Well, because, lengthening the spine (axial extension) takes conscious effort and, therefore, muscular work. Conscious muscular effort uses up excess energy that the body would be using for other things if we were not making that effort. The human body is an energy conservationist by nature. It would really prefer to expend as little energy as possible. So the spine has been constructed in such a way to be functional for our bipedal lives (for most of us, unless there is a disease or structural abnormality), including protecting the spinal cord and allowing for healthy CSF flow (without us having to monitor it) while we are at rest and involved in all kinds of movement.
Ah, movement. Riiiiiight. So, if it was true that we needed to consciously manage the optimal flow of our CSF by keeping a lengthened spine then wouldn’t the majority of asana that make up a yoga practice be contraindicated? What you say to me, bitch?! Think about it. Wouldn’t twisting (even if you try to do it with a “long spine”), flexing, extreme spinal extension like in…almost every backbend and lateral bending change the space surrounding the spinal canal? No! Actually, since CSF flows through the vertebral foramen, that space would be minimally affected by these movements. So it is neither true that you need to lengthen the spine for optimal flow, nor is it necessary to be alarmed about CSF flow when changing the shape of your spine.
There is a danger in this kind of misinformation. The danger of mistrust in the inherent strength and intelligence in the design of the human body. We need practices that reveal that design to us, so that we may use it to help, not be afraid of it and create beliefs and physical practices that solidify the false understanding the we must control every aspect of our beings. Try exerting that amount of constant control and you will go insane or just sleep a lot from over exhaustion and not be productive or not be any fun to be around. This is not to suggest that you shouldn’t sometimes be careful with your body, but you should question everything you are told by anybody, especially in a movement class. The human body was designed with certain basic functions meant to be outside of the realm of everyday awareness, so that we can put our attention to other things.
But you can, if you choose, create an awareness of almost every biological/physiological process. We (Mel and Kim) do it all the time! But we do it with the intention to understand what’s going on inside of us without fear or anxiety. Unnecessary fear is the last emotion one would want to embody.
1.) Essentials of Anatomy & Physiology, 2nd edition, Martini & Bartholomew.
2.) A Handbook for Yogasana Teachers, Mel Robin.