Judging from the editorial "Fitness Through Fidgeting" {Sept. 11}, which had some fun with an article I wrote for The Wall Street Journal about the health risks of modern office chairs, I assume that someone at The Post believes I may have touched off the latest neurotic exercise craze: squirming for health.

While this is intriguing speculation, I don't think it will happen anytime soon. For despite all the hoopla about physical fitness in recent years, according to a recent article in the government's "Public Health Reports," the facts are as follows:

"At this time . . . best estimates indicate that 41 percent to 51 percent of adults are sedentary while only one-third of all adults participate in exercise on a weekly basis. Just 15 percent are believed to expend an energy equivalent (1,500 calories per week) of known epidemiologic significance. Of those already regularly engaged in either group or solitary exercise, about 50 percent will discontinue activity at some time in the coming year. Moreover, less than 10 percent of sedentary adults are likely to begin a program of regular exercise within a year."

At least The Post got one thing right: my Wall Street Journal article about chairs was really about exercise, or more precisely, the lack of exercise endemic to modern office work. My basic point was that no chaircan cure this problem because sitting is the problem -- too much sitting leads to overweight, coronary heart disease, bone and muscle degeneration and mental and physical fatigue.

But is there no better solution to office inactivity than to squirm in an uncomfortable chair? At the center for Office Health and Productivity in Silver Spring, we have found that it is not necessary to be seated in a chair at all in order to perform most types of office work; in fact, it is possible to exercise while you are working.

In a study recently conducted with five word processors who walked on a specially modified electric treadmill, we demonstrated that they were able to walk and work simultaneously with no reduction in typing speed and accuracy, but with a considerable reduction in stress and back and buttocks pain.

Given their rapid adjustment to the new routine, it seems likely that after six months, these or similar production-level office workers could comfortably use an ''active office system'' for about half of their normal working day, and thereby burn the 1,500 calories per week required for multiple health benefits, including weight control.

I don't think there is much cause for alarm over The Post's fear that we may be on the verge of a ''fitness through fidgeting'' epidemic or, regrettably, any other type of mass infection of the exercising bug. I do believe that we should take very seriously an earlier editorial {Dec. 13, 1986} concerning the ''Sedentary Revolution,'' which is threatening to turn us into a nation of remote-control-punching glued-to-the-chair physical wrecks. With meaningful adult exercise participation in our country at a pitiful 15 percent level, we have got to be willing to try some extraordi?ary new approaches to fitness if our national health is not to be seriously impaired. Exercising while you work may well be an important step in the right direction.

Nathan Edelson

The writer is director of the Center for Office Health and Productivity Enhancement in Silver Spring.