Britisher Alan Aykbourn, who wrote the play "Bedroom Farce," inserted one scene especially for American audiences. A husband is confined to bed by a bad back, his suffering ignored by his pretty young wife hurrying off to a party. Left alone and trying to find a comfortable position, he drops his book on the floor and for the next five minutes goes through a series of gyrations as he tries to retrieve it.

In a very funny play, that scene provokes the loudest American laughter. As Aykbourn -- who calls Americans "a race of permanent agony from shoulders to waist" -- was confident it would.

Ayckbourn's diagnosis, however, doesn't go quite far enough. It's the lower part of the spine that generates most of the national agony.

We all know that America was built by strong backs, imported ones. But we've become a nation of back-achers: pinched nerves, slipped discs, sprains, chipped vertebra, and a host of spasms and aches, plaguing 7 million of us.

Until recently there were two standard treatments for back pain: pain-killing drugs and the scalpel. What has changed the picture is the proliferation of pain clinics. Their multidisciplinary teams of pain-control specialists offer numerous alternative treatment methods. The latest is the "back school."

The first back school on the East Coast opened early this year at the pain clinic of Associated Pain Consultants, Silver Spring. Modeled after the California Back School in San Francisco, the Silver Spring school offers three-week courses for patients whose physicians have recommended them.

Physical therapist Monta Powell gives these as the school's objectives: to teach people with back ailments to manage their pain, and to avoid further pain and injury as they learn to be more active.

"We never promise total pain relief," says Powell, "but we do help patients ameliorate pain and live active lives, despite some limitations. It's a process of retraining and instilling self-confidence.

"Changing bad muscular habits isn't easy, nor is learning new ways of using muscles. It takes will power, intense concentration and energy."

"What I look for when assessing patients," says clinical coordinator Marie Infante, who screens candidates for the school, "is those who would have the best chance of benefiting from the course.

"Having a definite goal is an important criterion. Men and women who want to get back to work are likely to be good candidates. Others are those who have had a series of unsuccessful operations to relieve back pain and are dead set against further surgery.

"Some people who have had chronic pain for years," she says, "really don't want to get rid of it. They've accommodated their lives to it and can't give up the psychic and financial rewards from their pain and disability. Others have drug-dependence problems caused by years of using addictive pain-relievers.

"Or people may be embroiled in family or other types of problems that use all their energy, leaving nothing for the back-school work. These difficulties have to be worked out first."

Age of participants has ranged from 15 to 60, equally divided between men and women, and including a clerk, housewife, pressman, roofer, secretary, truck driver, journalist, bookkeeper, high-school student and a telephone lineman.

Classes are limited to five patients, involved in both custom-tailored programs and group activities, one of which is the obstacle course. Score sheet in hand, Powell grades members on their normal walking and standing posture, the way they reach, bend, kneel, crouch, lift, twist, pull, push, step over an obstacle or crawl beneath it, and their usual positions for resting or sleeping.

At the end of three weeks, everyone again goes through the obstacle course. Scores improve considerably the second time around, after intensive retraining and practice.

Another basic skill learned at the school is backsliding. Everyone takes a turn at the huge, shiny red arrow painted on the wall. Back flat against the wall, the trainee slides down to a sitting position, feet firmly on the floor about 12 inches from the baseboard. After holding the sitting position a few minutes, the novice, misled by the ease of descent, tries to slide up. The back seems glued to the wall.

By strengthening their quadriceps, back-school participants learn to propel the back smoothly up the arrow.

In the specially designed classroom, areas are arranged to simulate work situations at home, in an office, plant or shop. Before assigning a task, Powell demonstrates the proper -- and most painless -- way to do it, explaining the body mechanics involved.

Class members practice the right way to carry laundry up and down stairs, to load and unload a dishwasher, to carry from the market and load and unload bags of groceries.

In the classroom's simulated office section, equipped with desk, chair, and file cabinet, office workers, for example, are taught the correct sitting posture, or "back ease" for long hours at desk or typewriter.

The refrain Mrs. Powell drills into her "students:" Flex the knees, tilt the pelvis, tuck in the buttocks and straighten the spine.

"Everyone should do this," she says. "It helps a strong spine to stay that way and protects a weak one. When you're standing in line at the bank or waiting for a bus, reminding yourself of those posture checkpoints pulls you right out of a slouch. It's a way of counteracting swayback and tightening the abdominal muscles that help keep the spine straight. People not only protect their backs by this exercise, but they look better."

In some instances, Powell visits the work setting to see what factors contributed to the back problem. One class member had injured her back in a fabric shop where she, as a saleswoman, had to pull bolts of material from shelves. After observing her pulling and lifting the bolts, Powell showed her how to remove and carry the bolts without jeopardizing her back.

"No matter how physically demanding a job is," says Powell, "there's a way of doing it that protects the back.

"A man in one of our classes had worked for 12 years on a job that required carrying heavy buckets of ink, stacks of books, and metal press plates. His back finally gave out.

"Once he understood the body mechanics involved and the proper way to perform each job, he practiced in the classroom and at home until he was able to return to his job and to handle it."

Alternating with physical activities are group sessions, in which therapists, nurses and pain specialists give talks on body mechanics, anatomy, diet and pain perception. As class members become better acquainted, they talk frankly about their worries and fears, the penalties -- beyond physical suffering -- of chronic pain. A common topic is sex: how to participate with a fragile back. Adapting her presentation to the sensibilities of a mixed group of men and women, old and young, Powell enumerates the "safe positions."

Cost of the three-week course -- for which physician-referral is necessary -- is $386. More information may be obtained from Associated Pain Consultants, 8808 Cameron St., Silver Spring, Md. 20910.