Why is this so?
For regular students, the answer is obvious: “Because it feels good!”
There is also a deeper reason: to be sensitive you have to be relaxed.
In this context, relaxed means that your muscles are not activated for exertion. Especially the extensors, which are along the back, should be resting and quiet.
In his book The Potent Self, Feldenkrais talks about his thinking process behind this starting position:
“The most complete elimination of the extensors in an act of spatial orientation would in fact be a complete contrast with our habitual experience and as little as possible associated with normal activity. Furthermore, the effort involved should be the smallest possible so that we can distinguish the slightest variations in muscular effort. For all sensations are so related to their causes that the slighter the cause, the smaller is the change that can be sensed. If we lift a heavy weight, for example, we cannot tell whether a sheet of paper is stuck beneath it or not. But on lifting a single sheet of paper we know at once if another one is stuck to it or not. Similarly, in daylight we do not notice a light bulb shining. But in the dark we can see the glow of a cigarette. Near an airplane, we cannot hear anything because of the propeller noise; in complete silence we can hear a fly or our own breath. Thus the intensity of the stimulus must be reduced if we want to become aware of small changes.” (1)
Taking this thinking into action, Feldenkrais developed a large number of movement sequences, which he called lessons and which students perform mostly while lying down, although sometimes in upright positions.
For example, a lesson might ask you to lie on your back and move your arms and head in one coordination and then in another. You are asked at the same time, “Please notice how you feel while doing it the first way, and the second.” Since you are able to do both, the distinction is usually small, but one way is preferable. By paying attention, you refine your ability to discriminate between these small differences and to make the choices that are best for you. Gradually, these awarenesses accumulate and deepen, and you find yourself moving in a way that makes you feel better.
Often, a whole lot better!
(1) Feldenkrais, Moshe. The Potent Self. San Francisco: Harper & Row, 1985. Page 135.