Always Learning,
First, anytime we are doing a drill or exercise in Systema (or any art or endeavor) it is very important that you understand your purpose for doing said exercises or drills. Every drill and exercise should have multiple layers of instruction and learning. A dozen people can be doing the same simple drill and each focusing on a different aspect, lesson, or piece of the drill/exercise.
Second, anytime we are doing a drill or exercise in Systema it is very important that we keep an open mind and focused awareness on the expected and importantly the unexpected lessons that the drill/exercise might be providing. Even the most mundane of daily tasks can provide a wealth of internal and external information and understanding.
Every drill should be unique to and for the person doing the drill.
On the op you asked, āHow should one position the head while crawling on the back using shoulders? If I leave the head relaxed on the floor, it interferes with the movement. If I raise it, strong pressure goes into the back of my head right away (after doing that for just a minute, five minutes later my head still hurts and I feel a little dizzy).ā
First, I would like to address the pain and dizzy. From reading your post, it sounds like you crawled for about a minute and after stopping your head still hurt five minutes later and you felt a little dizzy. Without being there and with the stipulation that I am not a doctor (or lawyer or Judge or Priest) and if wise you would take everything I say āwith the cynicism of one reading the internetā. Always Learning, I do not know the level of pain, nor the surface that you were crawling upon. I cannot tell if you had suspended your breathing or were holding your breath. I cannot tell if you were using your head (and neck) as a sort of weighted pendulum to āhelpā your locomotion. In general, often dizziness is an indication that breathing has fallen behind/under the level needed for the physical exertion required. You might be holding your breath or exerting and blowing out too much breath orā¦ any number of things.
The pain might be from imbalance of blood pressures; it could also be that you are using neck muscles and fascia around your face and skull too much.
Where a person holds their head while exploring a back crawl depends on the person and the nature of the work being explored or utilized. For myself, (and I am certainly no speed expert) I tend to float my head just above whatever surface I am traveling across. My hair (cut very short) brushes the surface of the mat/floor/ground, but the skin around my skull does not. I do not usually raise my head too much as that strains the neck as well as provides target for shrapnel, bullets, or boots. If crawling over obstacles then I do raise my head to help facilitate transition over the obstacles.
For me, the back crawl is not a speed contest across the room. It is an opportunity to open up my pecs and back. It is a chance to work in isolation the scapula. It is to better learn how to move from whatever freedom within my body that I might find. It is a solo massage to help me learn to deal with body strikes. It is a solo massage to help me work the spine and surrounding areas. It helps exercise some of the lymphatic system. The movements are a way of learning how to organize the body to move under restriction (standing or ground or in-between) It is a way of learning how to contact the ground with less fear. LOL should my shirt or jacket bunch up it is also a way to learn to deal with strangulation. Importantly it helps to tap down and strengthen the psyche and the body to prepare for deeper work. There are many more lessons depending just how deep one wants to delve. It can be a very humbling exercise.
For you Always Learning, perhaps the first lesson that the drill teaches has already been experienced? Go slow, take your time, do not hold your breath (unless that happens to be what you are exploring) Feel the joy in the movement and experiencing. Do not set goals but rather just experience and feel the movement, the many different ways of organizing your muscles and tendons to accomplish the simple goal of moving a single inch then the next. Learn to let the ground comfort, guide and teach you. There is a Russian sayingā¦a hard ground is an honest training partner.
Good luck
Regards
Brian King