We have more than 20,000 exercise instructors, but still no way of judging their competence, says Nick Walker
The rise and rise of the personal trainer proves that modern exercise is not an individual pursuit. The 6.3 million adults who keep fit or use weights hope to attain physical perfection quickly and safely - and under the watchful eye of a trained professional.

But anyone can start a gym or aerobics class. There are many fitness and exercise diplomas on offer. Look at Health and Fitness: "Jazzercise Instructor Certification", "Diploma in Sports Therapy", "Instructor Training Health and Fitness Certificates". But there is no industry standard. Inadequately trained staff are not only a physical threat (one man was allowed to jump from a sauna into a cold pool without being warned he might suffer a heart attack - which he did), but also a financial one.

Kathy Fulcher is a sports scientist with the National Sports Medicine Institute. "There are a whole number of qualifications but no sure way of telling whether it's a good or a bad course. I'm not so worried about qualifications, but levels of competence. You don't want to put yourself in the hands of someone who wouldn't know what to do if you had a chest pain while exercising, especially if you're pregnant, overweight or haven't exercised for ages."

Andrew has a long-term back problem and works out at a west London gym. "The instructor was sympathetic, but she didn't have any advice on how, or even if, I should exercise with this kind of injury. I used to do resistance training, but it can feel painful doing certain exercises so I stopped using machines, even though no one at the gym said I should."

David, who visits a gym four times a week, was given no instruction when he joined. "I learnt how to use the gym by watching other people. You can't go far wrong using a pec deck. It's different with free weights. You need to know which part of your body should be taking the strain. A lot of instructors rush you from machine to machine. The only reason they show you around is as cover for insurance."

It is estimated that there are more than 20,000 exercise instructors in the British fitness industry. The boom began with aerobics in the early Eighties but there was no central organisation to ensure proper instruction. Exercise to Music, which began in 1987, is the best known of all the aerobics instruction courses and has now established itself as a benchmark. Approved by the Royal Society of Arts, the course lasts 80 hours and covers everything from anatomy to setting up a class.

Aerobics is only one aspect; machine weights, free weights, cardiovascular machines and so on all require trained instruction. Over the next two months Scottish and National Vocational Qualifications (SNVQs), which aim to give an overall structure to vocational training, will embrace qualifications in the fitness industry. The Exercise Association, the governing body of the fitness industry, is responsible for supervising the introduction of SNVQs, and Annette Burgess is the SNVQ co-ordinator of the association. "We were aware of the hundreds of different organisations offering training, some of it good, some not so good," she says. "Employers have no way of knowing if a qualification is worth anything."

Critics say SNVQs have been introduced too quietly. "This is going to be a slow process," says Burgess. "People aren't all going to rush out to get requalified. It took a while for Exercise to Music to become recognised. The same applies to SNVQs."

The Exercise Association recommends that you check up on instructors before joining a gym, particularly if you are part of a "specialised population" - pregnant, injured, elderly or have never, or seldom, exercised. A gym should offer a personal fitness test and a programme tailored to the individual and, says one instructor, "not just a programme rattled off a computer".

If you do think you have been given bad advice and have suffered injury as a result, you should speak to the gym and then, depending on the response, contact a lawyer. The Exercise Association can tell you if an instructor is a member, but there is no means of testing an instructor's skills - though all should have a minimum level of qualification, preferably from the YMCA, the Physical Education Authority or the British Amateur Weightlifters Association. There should be at least one instructor educated to degree level, or by the American College of Sports Medicine, which has the only internationally recognised qualification.

"But that list is by no means exhaustive," says Burgess. "I am sure there are some courses I haven't heard of that are good, just as there are some that I know are unacceptable.... It's going to take some time before there is overall agreement."