They are as predictable as the flowers in spring. Clad in Lycra from head to toe, the new beginners arrive into the gym every January with great intentions and shiny new trainers. Regular gym-goers accept the influx with an air of resignation, knowing that many of them will give up within the month. It is estimated that about 50 per cent of the people who join a gym in January do not continue past February.

We've never had so many well-equipped gyms, so why is it so hard to become a regular exerciser? People give up after a few weeks because they have unrealistic expectations, according to fitness consultant Brendan Hackett.

"It takes at least six weeks for the body to acknowledge that the person is taking exercise. But most gyms don't tell people this. So when people don't see progress after a few weeks, they give up and go back to their old lifestyle." He points out that it can take years to gain weight so people can't expect to lose it instantly. "It's a long-term commitment."

But it's a commitment that few of us make. Less than 20 per cent of people in this State are regular exercisers. Some 40 per cent fall into the "intermittent exercisers", category while the remaining 40 per cent do not take exercise.

While new fads are introduced to gyms every year, there is no magical solution to getting your body in shape, according to Hackett. "You need to go to the gym at least three times a week. It doesn't really matter what exercise you do as long as it's continuous activity."

But with today's busy lifestyles, isn't it difficult to devote so much time to exercise? "It's all about motivation. Human nature is slow to change. But if you are motivated enough to change your lifestyle, you will find the time," he says. Hackett advises people to think of the gym as they would think of any other appointment. "If you have an appointment with the dentist, you will find time for it. If it's important enough to you, you will block out time for it."

Training with a friend or partner is another motivating factor. "If you are wavering, and you have a commitment to go with someone, then you are more likely to do it," he says. He also believes that people are more likely to continue exercising if they find the type of workout they like. "If you are a person who likes competition, then running on your own on a treadmill clearly does not suit you."

Derek Phelan, owner of the Maltings Fitness Training Club in Portlaoise, agrees. "If you take up an exercise which really interests you, you are much more likely to stick to it," he says. For this reason, the Maltings tries to match the activity with the personality.

While January may be a lucrative time for gyms, Phelan doesn't like to see people coming in and giving up after a month. "I often say to people, if you are not committed, then you would be better off not doing it because you are giving us a bad name and you are getting nothing out of it for yourself. So nobody is a winner."

As programme director at the Westwood Club in Leopardstown, Co Dublin, Beverley Hally is familiar with the January influx. Westwood is one of the biggest fitness clubs in Ireland, with 8,000 members. She estimates that membership increases by 30 per cent every January, but by the third week in February, many new members have gone.

"They say, yes, I wore the new trainers and tracksuit, I got a little sweaty but not too much, and now the novelty is gone." And just because some people get gym vouchers for Christmas presents, it doesn't mean they have a burning desire to get fit. "Someone might have said that they wanted to lose two pounds and suddenly everyone has bought them fitness gear and gym vouchers."

Hally has put a lot of thought into holding on to these wavering members. All beginners are encouraged to do a course, which lasts from four to six weeks. "This gets them into the habit of coming here two or three times a week, and because it's for a maximum of six weeks, they won't get bored," she says. Based on what they enjoy, programmes are drawn up and new classes introduced. Westwood now runs 96 classes a week.

She has travelled to gyms in other countries to keep up to date with the new trends and predicts that the stability ball will be the next big thing. This is a big, round ball, on which you balance while you exercise. The effort of balancing on the ball while exercising strengthens your "core", the area between your rib cage and lower abdomen, she explains. By far the most popular activity last year was spinning and she expects this to continue. Spinning is a group workout carried out on exercise bikes. "It's a total fat burner. We have over 20 instructors teaching it. It's so popular." Khai-bo, an aerobic routine involving kick-boxing and martial arts, is also growing in popularity.

Madonna can be thanked for the renewed interest in yoga, according to Mark Tooke, of the Jackie Skelly Fitness Centre in Dublin city centre. "Madonna does Astanga, an aggressive form of yoga, and people are very interested in that when they see her results," he says. "We do a yoga class at 7.30 in the morning and we have up to 20 people in that class."

He, too, is keenly aware of beginners' low boredom threshold, so the centre updates programmes every month. "And when people do a certain amount of workouts, say 30, they get a free T-shirt. When they do 50, they get a sweatshirt and when they do 100, they get a gear bag. It's just another motivating factor."

Tooke encourages new members to take classes as he feels that these can provide more motivation than a lonely session on the treadmill. "Somehow, the time never seems as long in a class."

But the gym can only do so much to motivate. "It's all down to willpower. The person has to want to change. Exercise is one of the very few things where you pay for something that isn't really that pleasant. So you need a lot of willpower."

Phelan says receiving a present of a gym voucher is "quite like getting a pet for Christmas. You can't let the interest go in the New Year. It's an investment in your health so if it is to work, you have to keep it up."