BOSTON -- I began walking before it was popular. Before I was a year old, I just sort of picked it up all by myself, without a coach or a single lesson. I don't mean to brag, but apparently I was a natural and, within a matter of weeks, had more or less mastered the trick.

Now I no longer walk. I am ''into'' walking or, if you prefer, power walking or striding. Indeed, the child who walked to get from one place to another has become an adult who walks merely to keep her waistline in place. The person who once did it barefoot has just become the owner of scientifically constructed, brilliantly marketed and redundantly named ''walking shoes.''

How did this happen? I ask myself regularly, as I lace myself into these specialized pavement pounders. How is it possible that the same soul who once owned exactly one all-purpose pair of sneakers has now added her fifth pair of ''shoes'' to the tennis shoes, running shoes (two styles) and squash shoes that form a small community on her closet floor?

For many years we have watched American entrepreneurs learn to make extraordinary profits selling expensive textbooks, lessons and equipment to help us do what we previously did naturally. This was, needless to say, the success story behind the sex industry from Masters and Johnson to the Playboy Channel to Victoria's Secret.

Now we are at the peak moment of a second cycle. I have joined the league of entirely willing, even eager, victims of a different marketing trend. I am another consumer who has been broken down into the sum of her activities, each requiring another set of shoes.

Remember when the baby boom receded and the population started to stabilize? In those yesteryears, the market moguls already knew that there was only one way to keep the sales chart growing. They would have to transform a constant population of consumers into an expanding market. They would have to multiply the existing number of consumers by a growing number of fully equipped ''life styles.''

Alas, individual consumers were only inclined to own one car at a time. But accessories were something else. We were gradually sold, for openers, entirely distinct sets of clothing for everything from leisure to success. Every time we grasped an all-purpose outfit, like jeans and sweats, the market subdivided it into designer jeans and evening sweatsuits. We eventually stopped wearing clothes and began wearing costumes.

The fitness boom added whole new frontiers to explore, at least for those who were properly equipped for exploration. (See the Banana Republic catalogue.) Today the savvy would no more wear aerobics tights on the golf course than fins on a treadmill. Anybody who would run in tennis shoes would probably play racquetball with a baseball bat. The more you did, the more you bought; one pair of shorts begat another.

The problem, of course, is that every complete set of costumes requires a quick-change artist. Consider the new entry into my fertile sports-shoe wardrobe. In order to go away for the weekend, I need to bring along my entire shoe collection, not to mention the Heavy Hands and headset. Before lacing up any one of these two-footed creatures, I have to plan. What speed? What distance? Is this a job for Walking shoe? Running shoe?

Merely striding to the tennis court has now become a two-pair operation: one to get there, another to play. Even crossing a street, I have to calculate the speed and whether it would be wiser for my back, heels and knees to change into running shoes for the dash across traffic.

I do take some comfort in the fact that the walking shoes in my possession are surely the very outer edge of this technological trend. This is the last frontier of the frantic fragmented consumer.

After all, having sold this consumer shoes to walk in, what is left? Sitting shoes? Shoes to watch television in? Costumes for the couch potato? What color do you think they'll come in? Robin's egg blue would be nice.