Is a bad back the curse of the caring classes? For a while your body may be strong and supple, lifting small children, bending down to correct work, reaching into difficult corners of the art cupboard. Then, one day, a twinge. Your body is trying to tell you something. But are you listening?

If you continue to slouch in front of the computer screen, stagger down corridors with piles of books and stoop over low tables, the twinges may well escalate into pain, chronic discomfort and eventually turn into injuries such as slipped discs or trapped nerves.

Conventional medicine can offer a range of painkillers and anti-inflammatory drugs, physiotherapy, corrective clothing (supportive corsets), surgery and traction. But what about the alternatives?

Three main systems try to re-educate the body to adapt better to the stresses and strains of working life. The Alexander Technique, the Feldenkrais Method and Pilates are all fashionable ways of correcting bad postural habits. They are intensive, involving small groups or one-to-one tuition, and thus expensive, but many who have followed courses swear that it has improved their lives - and not just their postures.

The Alexander Technique, says Carla Gray, has made the difference between being crippled and leading a full and active life. Carla, a lecturer in drama at an FE college, injured her back in a skiing incident when she was 22. At one point, it seemed as if she would never walk without pain. Conventional physiotherapy did little to ease her discomfort, but a course of 40 lessons with a trained Alexander practitioner left her fully mobile and able to continue her career. Carla says: “After a spinal fusion, when I had a dislocated and broken vertebra from a skiing accident, I had such bad pain I could hardly walk. I went intensively to the Alexander lessons for three months and the pain slowly went away. I went after work and I noticed that after you’ve been doing it for a bit you just don’t get the same aches and pains. It’s not first aid, it’s cumulative. You realise that bad posture is hurting you. It changed my life. I still go back for refreshers if I feel strain, and it sorts me out.”

Though Carla is still prone to backache when she is tired, she has only to lie down for 20 minutes in the reposeful position (supine, head slightly raised, knees slightly bent) favoured by Alexander to find that the strains ease.

Frederick Matthias Alexander (who died in 1955) was a Shakespearean actor working in Australia who, in the 1890s, discovered that muscular tension was causing his voice to seize up. Through trial and error, he found that reducing the tension in the neck allowed the spine to lengthen and the head to be carried freely.

Most of the Alexander Technique is aimed at getting students - they are not called patients - to learn how to experience this freeing sensation and make it a bodily norm. “The way you use yourself affects the way you function,” is the underlying principle.

Although it is possible to experience something of this sensation of release in small group introductions to the technique, it is generally taught in one-to-one courses of 20 to 30 sessions, generally lasting between 30 and 45 minutes. The teacher will explain how to observe and realign the spine in everyday movements, like sitting and rising.

In the course of these basic motions, the teacher keeps a light contact on the student, to feel how his or her body is contracting and tensing, and then guides the student into less stressed postures. Gradually, these “positions of mechanical advantage” should replace habitual tensing.

As well as physical benefits, the Alexander Technique reportedly brings spiritual and emotional improvements: students speak of becoming calmer and more focused. George Bernard Shaw was an early admirer, more recent devotees range from Paul Newman to Keanu Reeves, from Paul McCartney to Yehudi Menuhin. Nobel Prize-winner Professor Niko Tinbergen also swears by it.

Less widely known in this country than the Alexander Technique is the Feldenkrais Method. This attempts to treat the whole person using “bodily self-awareness”. Feldenkrais, an Israeli physicist and engineer who had once been a distinguished athlete, treated himself when an old knee injury flared up. To alleviate the pain and promote healing, he used insights from anatomy, judo and neurology. These observations are passed on in small groups, called Awareness through Movement, or one-to-one, with hands-on tuition, known as Functional Integration.

According to Ralph Strauch, a Californian exponent, the Feldenkrais Method “helps you learn to become more self-aware and to move in more efficient, less painful ways”. By showing the patient how to move with less tension, painful physical conditions can be alleviated. it is also felt that emotional tensions, held in the body by compressed muscles, can be dissolved, freeing the mind as well as the body. “It is amazing,” says Angi Hermann, a child-care worker who tried Feldenkrais in Canada, “how something so gentle can be so powerful.”

Even from one session of Awareness Through Movement, where the most strenuous exercise will typically be heralded by “Can you lift your hand without raising your shoulders?”, students are refreshed and invigorated. In Functional Integration, where the student lies on a low padded table and is guided through easier, more functional ways of moving, the experience of learning how best to raise the hands led Angi to “the best sleep I’d had for months”.

The gentle pieties of the Feldenkrais and Alexander techniques are less in tune with the spirit of the gym-going Nineties than Pilates. This latter technique, the work-out of choice for stars like Madonna, is both body conditioner and spine-improver. It was developed in the Twenties by Joe Pilates, a boxer who wanted to achieve “complete co-ordination of body, mind and spirit”.

Pilates concentrates on the “powerhouse” - a combination of stomach, bottom and lower back muscles. Mat classes, catching on fast in gyms like the Laboratory in north London (pound;8 for 90 minutes), offer students the chance to strengthen their weak backs.

An instructor helps the student into a posture and guides the student through a movement, with the student breathing deeply and evenly. The torso gradually strengthens, posture is balanced, and pressure removed from limbs. It takes months to build up the “powerhouse” to a peak level of fitness, but even the basic level can make students feel exhilarated.

As well as mat classes, there are six exercise machines. These are not the weight-resistance monsters you find in gyms but lengthening and strengthening isometric devices that take pressure off the joints.

The emphasis on breath control and on sustained fluid movement makes Pilates popular with dancers and gymnasts. Sarah Ward, a teacher from north London, is a devotee. “My back now carries my body, instead of me slumping round it,” she says.

The Society of Teachers of the Alexander Technique (STAT), Suite 20, London House, 266 Fulham Road, London SW10, please send an sae at 31p for list of registered teachers (more than 800 in UK). Tel: 0171 351 0828. Sessions range from pound;18-pound;25.Pilates Studio, 16 Balderton Street, London W1. Tel: 0171 495 0374. Studio uses machines pound;17 per 90 minutes; pound;150 for set of 10. Mat work from pound;8-pound;10 for 90 minutes. The Pilates Assocation at Body Control Pilates Studio, 17 Queensberry Mews West, London SW7. Send sae for list of practitioners. Tel: 0171 581 7041.Feldenkrais Guild UK, PO Box 370, London N10 3XA Tel: 0700 785506. Send sae for list of 40 UK practitioners. Individual sessions, functional integration, can cost pound;20-pound;25; Group classes are cheaper (pound;3-pound;9). AND RELAX...THE WAY TO BETTER POSTURE

* Each evening before you sleep, lie on the floor with a sizeable book under your head. Make sure your hips are in line with your shoulders, then slowly draw up your legs under you feet, your whole spine in contact with the floor. Then relax into the floor for 10 minutes, breathing slowly and evenly.

* Do not carry anything - children, shopping or work - on one shoulder or hip. Use a back pack.

* Start to notice how worries and hurries become held in your body. When having a tense phone call, say, try to release your hand.

* Become acquainted with the symmetry in your body, and experiment with consciously balancing even slight movements.

* Your head accounts for 10 to 15 per cent of your body weight. Carry it carefully.

* When you have to carry out difficult physical movements, try to think out how your body might manage them best, rather than focusing on how to achieve your goals: not how can I move that bookcase but how can I move that bookcase without damaging myself.

* How many muscles do you tense when sitting down in a chair?