Much has been said about exercise: "The only exercise I get is jumping at conclusions."

"When I feel like exercising, I lie down until the feeling passes."

"Chess is my game."

Physical fitness has been in so long so out. What is in is the new interest in decorating for physical fitness, as seen in some designs by top interior decorators.

When the 1980s' fit about fitness began, it happened outdoors. Fitness meant jogging or running or bicycling. Now exercise has been around long enough that people are beginning to think about making the process of becoming fit more comfortable, safer and more accessible.

It is, of course, perfectly possible to get plenty of exercise around the house without any equipment at all other than a broom and a mop. Running up and down the staircase can burn up a sizable number of calories. Trying to find out what's on the top shelf in a house with nine-foot ceilings is a fine stretch exercise. Making beds, washing windows, taking out the trash, all are enough to tire out your average football player.

All of these efforts can be coordinated with a calisthenic program.

But who among us is that practical? Name the pursuit, and 4,511 commercial manufacturers will figure out ways to equip it--and make you feel as though you need every bit of it.

Men are especially prone to the enticements of machinery. In case you didn't notice, the male takeover in the kitchen followed the invention of the Cuisinart. Men, not to be sexist about it, will do anything as long as there are buttons to be pushed, dials to be twirled and wires to be plugged in. Women prefer new enterprises which can be excuses for rearranging the furniture.

Decorating for exercise, the first ingredients might be a wall--preferably three walls--of mirrors, no rose-colored lights, please. The mirrors will give you a true, if unflattering, picture of just why you need to exercise.

Upon your first full-length glimpse of three sides of your anatomy, your immediate urge may be to pitch bricks at all the mirrors. But self-control, please! If you were happy with your image, you wouldn't be here to exercise, only to admire.

The mirrors are a great, if painful, help in showing you what you're doing right or wrong. It also will help to note if you're turning blue from the exertion and should quit before you faint. It will also reveal the black and blue marks where you've bumped yourself.

You won't be able to bear to look at yourself all the time, so the next thing you need in your exercise room is something to look at other than yourself. A window wall of glass is great, especially if it's on the south side and you can feel as though you're basking at the beach. Don't expect to watch the birds and the squirrels, your antics are likely to scare them into the trees. If you're not one who thinks it's important to be as uncomfortable as possible or the exercise won't work, you might include a television set. Reruns of "M*A*S*H" can make you feel better by contrast. A video player with tapes of exercises would be an enormous help. Second best would be an audio tape of calisthenics.

Ah yes, one more necessity: a soft bed to drop on after you've done your bit.

But there's lots more that could be added. Harriet Blake's HELP column on Page One tells about all the devices that you can buy to mortify the flesh. Carol Krucoff's companion story tells how she hangs from her heels in a hallway.

Other refinements, you might consider are a sauna, a whirlpool spa or hot tub, or, best of all, an indoor swimming pool. That's the ideal. But not many people are so lucky or wealthy.

Only a few interior designers have started to think about the exercise room as an interior design problem. As Sarah Jenkins of W&J Sloane puts it, "Most people just stick their exercycle in the closet along with their clothes."

Jenkins has set up in the Connecticut Avenue Sloane's a series of model rooms which together make a four-room town house or apartment dedicated to the active life. Sloane's had help from the Executive Fitness Center of New York (and coming to Washington soon) and Ocean Spray Grapefruit Juice.

"We used contemporary fabrics from the Signature Collection in Herculon," said Jenkins, "because they are easy to take care of and wear well. It's hard to tell that the new fabrics are man-made."

In the living room, a curved upholstery group in gray and lilac "popcorn" weave by Lambert opens into a bed (about $2,000). The floor is covered in Herculon camel industrial carpeting by Wellco Heathertex at $15 a square yard. The three circular tables are by Gampel-Stoll. Jenkins thought of this room for aerobic exercises. The Chinese screen could hide a stationery bicycle.

In the dining room, the floor is covered in a Rustic II, a shale-gray tile by Ceramicus Romaney. The glass and acrylic dining table is by Swaim ($2,495). The six dining chairs are in pine with a rush seat ($320 each) for a casual air. The prints on the wall think healthy: grapefruit.

In the kitchen, a bar at the end of the room is floored in tile. Both open and closed cabinets hang over the counter with baskets decorating the top. A ballet bar is set against a mirrored insert, for exercises while you wait for the roast.

The bath, floored in Ceramicus greige-colored tile, has a Lambert navy velvet day bed ($1,200) in case your bath was too fatiguing, a Millmode glass table, and a Swaim glass pedestal table. An oriental carpet on the floor adds to the luxury. The towel racks are really ballet bars. An exercise cycle sits stubbornly in the middle of the floor where you can't miss it. And a tall scale makes it easy to see what you weigh without actually having to bend over, something you may not do so well after all that pedaling. Shelves on either side of the sink hold not only towels but a few vases and ceramics to relieve the eye.

The bedroom, according to Jenkins, was planned with the idea that no one should know how you maintain that perfect body. "Everything is concealed," she said. Vertical blinds close off the windows. The gym outfit is in the closet, the trampoline under the bed. The queen-sized bed is by Dillon, lacquered in a cream color and covered with a pink, peach and beige stripe. The headboard extends to become a pair of chests (platform bed $375, dresser $695, storage headboard $285, two night table chests $400 each). The two chairs by Lambert with Herculon covers convert to beds. A poster of New York City and a steamship both match the Art Deco inspired furniture.

The second bedroom here has been converted into a gym guest room -- though you might have to select your guests with an eye toward their flexibility. Two of the three ottomans by Lambert ($600 each) convert to beds for guests. A third ($500) doesn't. The artwork gives you no relief from the matter at hand -- posters of balloons, the Boston Marathon and a bike.

One wall is mirrored, as you might expect, with another of the ubiquitous ballet bars across it.

The equipment all comes from the Executive Fitness Center. To use all the devices, you'd have to quit being an executive and exercise full time. Then how would you pay for it all?

Most of them look as though they came from a medieval torture chamber and I suspect I would feel as though I had been in such a dungeon if I tried one. But those who persevere will,no doubt, be better for it, if they live through it.

Here are a few: a leg press and leg squat accessory, $1,625; a Monarch trainer ergometer, $405; a WCSDI scale, $200; a Dyna Row rower, $275; an abdominal conditioner, $370; a chrome floor ladder (for crawling around the floor?), $200; a leather jump rope, $14; 12-inch ballet bars with brackets, $235; 4-by-6-foot exercise mats, $3.20 a square foot, and, in case each session seems forever, a timer, $59.95.

Sloane's isn't the only one thinking exercise. A few years back, interior designer Claus Mahnken did a bachelor pad for Woodward & Lothrop with exercise equipment on a podium. Keith Babcock did another with all sorts of carpeted platforms for a Washington Symphony Decorators Show House.

Interior designers Gary Lovejoy and Jean Maxwell did one in the American Institute of Designers showhouse in 1980. They took a third-floor room under the roof and turned it into a show stopper. The walls were gloss white. The floor was black Pirelli tile ($4 a square foot). One wall was mirrored. A double row (60 feet) of neon in a cool blue ran on two walls ($1,600). Track lighting cross the ceiling at a diagonal with pink spot bulbs to soften the effect. A wood and chrome ballet bar was on one wall, a workout bench with weights set at a diagonal. A diamond-shaped metal grill covered the windows.

For relaxation, after you've done your duty, Lovejoy/Maxwell built a platform for a black chinz-covered Futon (a Japanese cotton-filled mattress, about $350) with a head roll. Red apples in a black lacquer bowl and a green cactus plant completed the picture.

With today's emphasis on fitness, there's little question that the exercise room will be one of the standard rooms in the '80s house. Just think how fit we'll all be -- and how tired.