FIDGETING, it seems, can be good for you. That, at least, is the conclusion of Nathan Edelson, a student of office health and productivity. Writing in The Wall Street Journal, Mr. Edelson says that the backache problems that bother many sedentary workers aren't likely to be relieved by the "ergonomic" chairs on which employers currently spend so much money. Nor does he put much stock in the advice of some experts for workers to get up from their desks at regular intervals or perform certain little exercises while sitting.

In fact, writes Mr. Edelson, "Until the day that office equipment is available that takes the place of exercise, my suggestion is that when you buy a new chair, get a straight-backed hardwood model like the chairs you used in school. By constantly squirming, you will do more to prevent or relieve your backache than you will by sitting still in the most expensive ergonomic chair now on the market."

Now, ergonomically speaking, Mr. Edelson may be absolutely correct, but we wonder if he has any idea what he might have just unleashed. For by associating squirming with exercise, Mr. Edelson automatically puts it in the category of good things that many thousands of people will take up and then insist on doing and overdoing until they collapse in a heap.

The usual cycle is this: the activity acquires a more glamorous name ("speed squirming" or "high-impact writhing"), which means it requires increasingly expensive kinds of sportswear and equipment (solid oak squirming chair, triple-laminated in black walnut, maximum discomfort guaranteed, cost: $1,500) and intensive competition, which quickly escalates from fitful 10-kilometer fidgets to long-distance squirmathons. After a time, it is reported in medical journals that the activity in question may damage some part of the anatomy (in this case, we won't speculate on which one). The allegations are fiercely disputed in the half-dozen magazines devoted exclusively to fidgeting and squirming, but in time nevertheless many people are persuaded to curtail their fidgeting. Some give it up entirely and go back to sitting still at their desks. Then they get backaches again -- which is probably only slightly worse for your desk-job efficiency than nine-to-five twisting and turning.