Why is it so easy to hold one’s arm up in the air for a long time, but not one’s leg?

The muscles and joints in the torso will act like a scaffold to hold up the arm — and in the process, writing on a chalkboard is just a modification of the joint positions, and effortless, if one is relaxed.  So, in theory, if one were to get a good working relationship with one’s pelvis, lower spine, and thighbones, could one effortlessly write one’s name in the air with one’s big toe?

It seems a reasonable theory:  making it happen in a reproducible manner, on the other hand, is difficult.  The typical methods for attempting it tend to involve lots of strain and even more people injuring themselves.

That’s one example, which comes from savate: if one were to do savate well, that’s a given for a style which requires its “competent” practitioner to be able to ring a wine glass with one’s toe without breaking it or spilling the wine.  Savate requires the “chamber” (movement of the knee to shoulder without ventral collapse of the spine), “pivot” (full-body longitudinal spinal torsion) and “balance” (ability to sacrifice and regain balance intentionally) not merely as principles, but as movements which are “price of entry” in order to perform correctly (non-injurious to self). 

Now, notice that I didn’t say well.  Quality of performance implies dynamic performance — sparring, etcetera, where one is actually interacting with another person.  The “static” performance of a kick, punch, etcetera, without the stress of actually combat (sportive or “earnest”) is a sufficiently high barrier that the vast majority of martial artists wash out without developing a level of skill markedly superior to an opponent with low skill and extensive physical strength/conditioning. 

The same holds true with other martial arts.  Not that these are the “barrier” (necessary but insufficient) movements — those vary by discipline.  Tai chi and aikido, for instance, rely heavily on the “ridge pole” movement technique(longitudinal rotation of the body driven by the pelvis, but individuating the hips so that they are either isolated or involved at will) often described, sloppily I might add, as “moving from your center.”

Violin has the same pre-requisite: the bowing elbow must remain stable.

Each and every one of these (and one could create quite a laundry list, covering nearly all sports, music, and most games) benefits from elegant use fo the skeleton making just enough coordinated movements of the joints, rather than overusing one or two joints –or its opposite, involving MUCH more movement than is actually necessary.

But I’m not sure how to get from point A to point B.