In fully relaxed conditions, when the muscles and tendons are stretched, the hand assumes a position that is neither fully open nor fully closed. Its degree of opening depends on how it is supported: if it rests on the back, it tends to remain semi-open, because the fingers fall onto the palm under their own weight; if it rests on the palm, then the weight of the hand and arm crushes it so that it remains practically open or, conversely, closed into a fist. The different relaxation positions occur depending on the balance between the force of gravity, the weight of the hand and the friction with the support surface .
Postures that seem natural, such as that of the extended hand, do not always correspond to a state of muscular relaxation. In fact, putting your fingers straight takes an extra effort. The same happens with the head. It remains upright all day seemingly effortless, but actually achieves it thanks to the mediation of the powerful muscles of the neck. Without your work, the head would be as unstable as that of a newborn.
