In early February, I started a sweaty experiment in the privacy of my own home.

Three times a week, without exception, no matter how I feel or what’s happening in my busy day, I change into t-shirt and shorts, strap on a pair of old sneakers, and slink upstairs to the elliptical.

The workouts are nasty, brutish, and… not so short. I hate them. But that hasn’t stopped me yet.

The idea of regular exercise may not seem like a big deal, especially if you’re an active, outdoor kind of person. But for me it has been a big change.

I spend most of my working days at a desk. As I read and write my way through the hours, my angle may change slightly as I tilt thoughtfully in my chair; I may go up and down the stairs eight or ten times — more if the basset hound isn’t feeling terribly continent; I might walk around a bit. From time to time I’ll involve myself in some physically demanding home renovation or repair. But those days are fewer and farther between as I get older.

Let’s be honest. I’m forty-seven years old. I have, shall we say, a generously proportioned body. There’s a history of heart disease in my family.

Doctors have been on me for years — decades, really — to exercise regularly. And for some stretches in my life, when working with my hands has crowded out the life of the mind, I’ve been quite active.

But I’m at the tail-end of a long stretch of writing, with the promise of more to come. Thus, February’s experiment.

My main concern is health, but I’d be lying if I said that vanity had no role in my decision to start working out. I don’t think of myself as a huge guy, but the garment industry begs to disagree. I’ve yet to meet the person who delights in adding Xs to his shirt size.

Over the years, I’ve had my share of fit friends. I always envied the righteous enthusiasm that lit their eyes when they talked about their daily runs, or their soul-satisfying swims; above all, the way that exercise made them feel good. Stories of the euphoria that accompanied a long, hard workout kept me going when I was younger — until I realized that the euphoria was a reward for members of an exclusive club. It seems to me — and a few recent genetic studies bear this out — that there are people who were born to exercise, and others who were born to sit.

Apparently, I’m a sitter, not a runner. Running makes me feel bad while I’m doing it and even worse afterwards. Not to mention the fact that it takes several dripping hours for my body to cool down.

For those of you who would interject, “You’re not doing it right!”, I’ll just say that feeling bad has been my experience of vigorous exercise ever since I was little. Name the sport; name the warm-up and cool-down regime; name the time of day or season. It has ever been thus.

“No pain, no gain!” you say. “The whole point of exercise is to trade short-term discomfort for a long-term health benefit.”

Well, maybe. Except in my case, the long-term health benefit has always been maddeningly hard to detect, and the bonus that most of my fit friends enjoy — they look good in clothes! — has never been part of the program. Some athletes look like muscled hunks; others look like offensive linemen. You can lump me in with the linemen.

Exercise is not, and has never been, my friend. It’s as simple as that.

Then again, heart disease is not my friend, either.

Let me just say, for the record, that embarking on this kind of experiment isn’t something to be taken lightly. I had the endorsement of my physician, whose green light was predicated on my overall health. Our elliptical, an inexpensive Schwinn model, has a built-in monitor that lets me keep an eye on my heart rate, so I can make sure I’m not overdoing it.

I’ve now completed forty of these workouts over four months. My careful notes reveal good progress. I’ve steadily increased the elliptical’s resistance, and, at the same time, picked up the pace. I’m getting stronger and running farther.

This is all good. Very good. I’m sure my heart is thanking me.

But guess what? I weigh exactly the same as I did in February. My clothes fit me the same. There’s still no sign of that elusive euphoria.

I will say this: the regular workouts have made me feel virtuous. And I did breathe a little better through the spring allergy season.

As for the rest, time will tell.